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An experimental investigation of the pointed forebody aerodynamics Stewart, Alan Charles 1988

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AN  EXPERIMENTAL INVESTIGATION POINTED  FOREBODY  OF THE  AERODYNAMICS  By CAPTAIN ALAN CHARLES B.Eng.,  A  THESIS  STEWART  T h e Royal Military College  SUBMITTED  IN P A R T I A L  of  Canada,  FULFILLMENT OF T H E REQUIREMENTS  FOR T H E DEGREE O F MASTERS  OF APPLIED  SCIENCE  in THE  FACULTY OF GRADUATE  (Department  We  of  THE  Mechanical  accept this thesis as to the  required  UNIVERSITY  Alan  STUDIES  Engineering)  conforming  standard  O F BRITISH  August ©Copyright  1981  COLUMBIA  1988  Charles Stewart,  1988  In presenting  this thesis in partial fulfilment  of the  requirements for an advanced  degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department  or  by  his  or  her  representatives.  It  is  understood  that  copying or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department of  Mechanical  Engineering  The University of British Columbia Vancouver, Canada Date  DE-6 (2/88)  2 August, 1988  ii  ABSTRACT  An  experimental  aerodynamics angle  of attack,  missiles. the  low  been  zero  conducted  yaw,  Towards this speed  alleviation tip  has  investigation  wind  devices  generated  with  side force  tunnel  with  of  The  helical  vortices,  presence  of  nose-booms;  a  of  strakes;  reducing  the  the  with  the  the  side force of  50%  with  been  fashion.  up  porous  achieved.  aircraft  standard force  compared  a  delta  side  and  applications  pointed emphasis  by  is  passive  and  flow  its  several cone tip a  cone tip. assessed  porous The  over  a  tip;  50% w i t h and  up  also  active  field,  geometries: tip;  tip  of  of  flight  data.  in  force  by  the  model  are  a family  spinning  effectiveness range  side  the  and  tested  induced  on  high  aircraft  model was  and  the  of  nose-boom each tip  in  conditions,  Reductions  in  n o s e - b o o m s ; 88% w i t h  delta  strake  tips;  to  nose-booms  have  applicability are  forebody  on  fighter  effects  corresponding standard  to  The  experienced  asymmetric  in the  tips; as well as  particular  various  investigated  set  the  end, a slender cone-cylinder  installed.  pair  into  75% and  with  spinning  practicality  considered, however,  of  these  only  in a  devices  in  preliminary  iii  TABLE OF CONTENTS  1  INTRODUCTION 1.1 1.2 1.3  2  MODELS AND TEST PROCEDURES 2.1 2.2 2.3 2.4 2.5  3  Cone Model T i p Geometries Wind Tunnel Instrumentation T e s t Procedures  RESULTS & DISCUSSIONS 3.1 3.2 3.3 3.4 3.5  4  P r e l i m i n a r y Renarks A B r i e f Review o f t h e Relevant L i t e r a t u r e Purpose and Scope o f t h e I n v e s t i g a t i o n  Standard Cone T i p R o l l T e s t s Nose-Boom T e s t s D e l t a Strake Tests Porous T i p T e s t s Spinning T i p Tests  CONCLUDING REMARKS  1 1 4 13 15 15 17 21 23 25 28 28 37 43 52 56 65  4.1  Conclusions  65  4.2  Recommendations  69  BIBLIOGRAPHY  73  APPENDIX I: INTEGRATION OF PRESSURE DATA  78  iv LIST OP  FIGURES  F i g u r e 1-1  E f f e c t of angle of a t t a c k on l e e - B i d e flow f i e l d  F i g u r e 2-1  The at  standard  the  cone mounted i n the wind t u n n e l  an angle o f a t t a c k o f 30°  1  F i g u r e 2-2  An exploded view o f the cone-model  F i g u r e 2-3  A s e c t i o n view o f the cone model  F i g u r e 2-4  The  b r a s s apex cone t i p c o n t a i n i n g  pressure  1  16  taps  F i g u r e 2-5  The  porous cone t i p  F i g u r e 2-6  The  b e a r i n g housing  F i g u r e 2-7  A f a m i l y o f nose-boom t i p s w i t h the s t a n d a r d t i p shown f o r comparison A f a m i l y o f d e l t a s t r a k e t i p s used i n the t e s t program  F i g u r e 2-8 F i g u r e 2-9  cone segment  A schematic diagram o f the low used i n the experiments line  speed wind  F i g u r e 2-10  The s c a n i v a l v e p r e s s u r e arrangement  F i g u r e 2-11  The B a r o c e l p r e s s u r e t r a n s d u c e r e l e c t r o n i c manometer  F i g u r e 2-12  Instrumentation layout f o r pressure measurements u s i n g a S c a n i v a l v e and a Barocel transducer  tunnel  switching  and  F i g u r e 3-1  Pressure d i s t r i b u t i o n at a reference s t a t i o n as a f f e c t e d by the angle o f a t t a c k , f o r the s t a n d a r d t i p a t z e r o r o l l angle  P,  F i g u r e 3-2  P r e s s u r e d i s t r i b u t i o n a t a r e f e r e n c e s t a t i o n P, as a f f e c t e d by the angle o f a t t a c k , f o r the s t a n d a r d t i p a t a r o l l angle of 300°  F i g u r e 3-3  V a r i a t i o n o f the s i d e f o r c e c o e f f i c i e n t f o r the s t a n d a r d t i p model w i t h p i t c h and r o l l  V  Figure 3-4 Figure 3-5 Figure 3-6 Figure 3-7  Figure 3-8  Figure 3-9 Figure 3-10 Figure 3-11  Figure 3-12  Figure 3-13  Variation of the normal force coefficient for the standard tip model with pitch and r o l l .  33  Effect of the standard tip r o l l position on the side force at a pitch angle of 50°  35  Effect of the standard tip r o l l position on the normal force  36  Effect of boom length on variation in the side force coefficient with pitch and r o l l attitudes: a) Lb = 4.13 cm, Lb/L = 0.27; b) Lb = 3.18 cm, Lb/L = 0.21; c) Lb = 2.54 cm, Lb/L = 0.17 d) Lb = 1.91 cm, Lb/L = 0.125; e) Lb = 1.27 cm, Lb/L = 0.083; f) Lb = 0.95 cm, Lb/L = 0.063 g) Lb = 0.64 cm, Lb/L = 0.042; h) Lb = 0.32 cm, Lb/L = 0.031; i) Lb = 0.16 cm, Lb/L = 0.010  38 40 41  Magnitude of the maximum side force coefficient with varying nose-boom length including the standard tip case  42  Normal force variation with pitch angle and r o l l orientation for the 4.13 cm nose-boom  44  Normal force coefficient variation with pitch incidence and nose-boom length  45  Variation of the Bide force coefficient with pitch and r o l l angles for the 3.18 cm delta strake  46  Pressure distribution, at the reference station P, for the standard tip at a yaw incidence of: a) (3 = -10° b) B = +10°  48 49  Variation of the side force coefficient with pitch and yaw angles as affected by the delta strake length (aspect ration = 1): a) standard tip, Ls/L = 0; b) Ls = 0.32 cm, Ls/L = 0.021; c) Ls = 0.64 cm, Ls/L = 0.042 d) Ls = 1.27 cm, Ls/L = 0.083; e) Ls = 1.91 cm, Ls/L = 0.125; f) Ls = 2.54 cm, Ls/L = 0.167; g) Ls = 3.18 cm, Ls/L = 0.208  50  51  vi F i g u r e 3-14  F i g u r e 3-15  F i g u r e 3-16  F i g u r e 3-17  F i g u r e 3-18  F i g u r e 3-19  F i g u r e 3-20  F i g u r e 3-21  F i g u r e 1-1  E f f e c t o f the s t r a k e of the s i d e f o r c e  l e n g t h on the magnitude 53  V a r i a t i o n o f the normal f o r c e c o e f f i c i e n t with p i t c h and yaw a n g l e s f o r a s t r a k e o f 3.18 cm. E f f e c t o f the s t r a k e force c o e f f i c i e n t  . . .  54  l e n g t h on the normal .55  S i d e f o r c e v a r i a t i o n as a f f e c t e d by the p i t c h a n g l e and nose-boom l e n g t h a t t i p s p i n o f 2000 rpm  57  E f f e c t o f the nose-boom l e n g t h on the s i d e c o e f f i c i e n t a t 2000 rpm  59  force  S i d e f o r c e v a r i a t i o n as a f f e c t e d by the p i t c h a n g l e and s p i n r a t e f o r a 1.27 cm nose-boom  60  E f f e c t o f s p i n r a t e on t h e s i d e f o r c e f o r a 1.27 cm nose-boom  61  coefficient  The normal f o r c e c o e f f i c i e n t as a f f e c t e d by: a) the nose-boom l e n g t h a t a s p i n r a t e o f 2000 rpm. . . .63 b) the s p i n r a t e f o r a 1.27 cm nose-boom 64 D i v i s i o n o f the cone s u r f a c e  i n t o a r e a segments  78  vii LIST OF SYMBOLS  Ab  base a r e a of c o n e , TCD /4  a  local s p e e d of s o u n d  C  perimeter  CN  c o e f f i c i e n t of normal  2  of a r e g u l a r  p o l y g o n of n s i d e s  force,  normal f o r c e / ( q « A b ) Cp  c o e f f i c i e n t of p r e s s u r e ,  P/q  Cs  c o e f f i c i e n t of s i d e f o r c e , S i d e  D  cone base  diameter  L  total cone  length  Lb  nose-boom  length  Li  l e n g t h of the cone to the station  Ls  strake  M  Mach n u m b e r ,  n  an integer,  P, P«  local a n d r e f e r e n c e  Force/(qAb)  i  length  pressures,  V/a  n u m b e r of s i d e s of a p o l y g o n f r e e stream  static  respectively  q  f r e e stream  d y n a m i c p r e s s u r e h e a d , (1/2JPV**  Re  Reynolds number,  Ri  r a d i u s of the cone at the station  Si  l e n g t h of the s i d e of a r e g u l a r  V , V»  local a n d f r e e stream v e l o c i t i e s ,  a  a n g l e of a t t a c k  0  yaw  6  cone  angle half-angle  VD/u i  polygon respectively  viii P  density  0  roll angle (in the circumferential direction) to reference point on the surface of the cone  8  angular position in roll w.r.t. a fixed reference frame  6j  circumferential position on the cone surface at the point i  u  viscosity  ix  ACKNOWLEDGEMENTS  The  timely  completion of t h i s t h e s i s would  not have been  without t h e a s s i s t a n c e of many i n d i v i d u a l s a n d o r g a n i z a t i o n s . foremost g r a t i t u d e i s e x p r e s s e d Modi.  First and  f o r t h e g u i d a n c e a n d c o u n s e l of Dr. V.J.  His c l e a r i n s i g h t i n t o t h e t e c h n i c a l p a r t of t h e t h e s i s a n d h i s  invaluable editorial skills are greatly The  comraderie  and  fellow g r a d u a t e s t u d e n t s  The  appreciated.  occasional  brainstorming  with t h e i r e x p e r t i s e w h e n needed. Len  with  my  and progress faster.  machine a n d i n s t r u m e n t a t i o n  particular,  sessions  h a v e made my e n t i r e m a s t e r s p r o g r a m i n c l u d i n g  the t h e s i s , b o t h more e n j o y a b l e  In  possible  Drakes  shop technicians  Their assistance  contributed  have helped  me  has been invaluable.  h i s exceptional  model  making  skills. The  Canadian Armed  Forces  of t h i s p o s t - g r a d u a t e e d u c a t i o n financial  assistance  Canadian years.  Armed  completely  a n d to them  and the opportunity.  Forces  have  been  covered  all financial  costs  I am g r a t e f u l f o r b o t h t h e Many  particularly  local  agencies  helpful over  of the  t h e last  S a r g e n t Daniels o f J e r i c h o Detatchment a n d t h e Photo S e c t i o n of  Canadian Forces  Base C h i l l i w a c k d e s e r v e s p e c i a l mention.  1 1 INTRODUCTION  1• 1  PreliminaryRemarks  It is well known that certain flight vehicles, particularly the STOL and  fighter airplanes, often  angles of attack.  undertake maneuvers  It has been observed  that,  at relatively  high  depending upon  the  geometry of the aircraft and its angle of attack, it may experience a large side force, of uncertain direction, resulting in a yawing moment that may prove difficult to control.  Association of a side force with an  object that has a plane of symmetry intrigued aerodynamicists, however, it was  quickly established  pointed forebodies. the fuselage. propellers, etc.,  to  be related  to the  fluid  mechanics  of  In the case of an aircraft, it would be the nose of  Tip-tanks, bombs, missiles, also present  launch vehicles,  pointed forebody  geometries.  hubs of Normally,  such a pointed forebody is incorporated as a part of the streamlined structure to reduce drag, increase stability and aid in generating lift. Although a simple cone geometry  is sometimes used, a more common  pointed forebody is a tangent ogive or its variation. As discussed by Ericsson and Reding [1], an object with a slender forebody, depending upon its attitude in pitch, exhibits four distinctly different types of flow patterns as shown in Figure 1-1. At low angles of attack the flow field is usually symmetric and essentially attached.  As the pitch angle increases the streamlines are  swept downstream from the windward to the leeward side of the body symmetrically about the pitch plane.  Figure 1-1.  Effect of angle of attack on the lee-side flow field.  3  A t h i g h e r a n g l e s of two  counterrotating,  side  of  the  At One  still  of  exerts a lower  Although  this  literature  in  the  wake  pair  flow  near  vortices the  apex  Typically,  form  on the  leeward  and  continuing  well  of  attack  the  vortices  strength  p r e s s u r e on the which is the  pattern  has  been  become  and  position  body  than the  subject  two v o r t i c e s , effectively  such  of s t u d y  described  and  there  asymmetric. that  other.  in this  analyzed  it  This thesis. in  c a n be f o u r ,  the  six  or  quasisteady vortices.  a n g l e s of  results  or  changes  side force  t e r m s of  stationary  becomes separated.  stationary  at  angles  aerodynamic  more s t a t i o n a r y  flow  object.  the  results in a net  At  starting  higher  vortex  the  symmetric,  object,  d o w n s t r e a m of the  attack  attack  approaching  vortices start and  the  to s h e d .  side  force  flow  normal  A vortex becomes  to  the  slender  street o r a more  oscillatory  or  body  random  disappears  entirely. T h e o n s e t of a s i g n i f i c a n t attack  approximately  of  same o r d e r  the  On  aircraft  rudder lead  is  to  this  of  the  cone  magnitude  would  partially  the  twice  side force usually  shadowed  situation  where  by the  half-angle, and  as the  correspond  to  the  a t t a c k , it  is  not  craft  c a p a b l e of  side  force  the  for  flights  large  phenomena.  at  most  be  angle  attack  when  the  fuselage.  This  may  order  magnitude  of  force  the  is  aircraft.  within  of  an the  the  can  an  a n g l e s of  Included  peak  by  side force is u s u a l l y at  a problem  its  generated  wake  side  at  of  lift  larger than the correcting force available from A s t h e o n s e t of  o c c u r s at a n angle  of  rudder. a fairly  high angle  Only highly  attack this  forebody.  maneuverable  have experienced group  of  are  the  the  latest  4  f i g h t e r s , t h e F-16, F-18, etc., t o g e t h e r with a i r - t o - a i r a n d s u r f a c e - t o - a i r missiles.  F o r reasons  of nose  shape,  flight  attitude  and  the  Mach  number t h e S p a c e S h u t t l e l a r g e l y a v o i d s t h e s i d e f o r c e phenomena. The forces  e f f e c t i v e n e s s of t i p geometry i n p a r t i a l a l l e v i a t i o n of t h e side  experienced  here.  The  dominated, exhibits  by  flow  and  pointed  field  f o r e b o d i e s i s t h e topic  is fully  primarily  three-dimensional,  governed  p u z z l i n g , seemingly  by  random  unsteady,  the boundary  characteristics  of i n v e s t i g a t i o n  layer.  thus  vortex It also  making  this  p r o b l e m of c o n t e m p o r a r y i n t e r e s t a n d s i g n i f i c a n c e , r a t h e r c h a l l e n g i n g .  1.2  AJBrieL-BeYJew QL.the.JRekvant Literature The  Allen  side f o r c e p h e n o m e n o n  and  Perkins  experimented investigations  with  [2] i n 1951.  forebody  Since  various aspects  [2-4] c o n c e n t r a t e d  v a r i o u s nose geometries. of t h e nose.  was f i r s t  Only  n o t i c e d a n d documented  then  many  of t h e problem. on  flow  past  recently  have  Most of t h e e a r l y  slender cylinders  They focused their study  more  researchers  by  with  on t h e flow f i e l d a f t  [5-13] h a s t h e f o c u s  moved  to t h e  nose itself.  A r e v i e w of t h e l i t e r a t u r e s u g g e s t s t h a t t h e e a r l y r e s e a r c h e f f o r t s can  be  broadly  divided  i n v e s t i g a t o r s who  into  two  groups.  On  one  hand,  we  c o n s i d e r t h e side f o r c e phenomenon  to be  boundary  l a y e r g o v e r n e d a n d t r e a t i t as a logical e x t e n s i o n of t h e c y l i n d e r flow.  The  Reynolds number  two-dimensional  dependence and the effectiveness  of some of t h e s i d e f o r c e a l l e v i a t i o n d e v i c e s seem t o s u p p o r t Other  researchers  suggest  t h a t t h e side f o r c e  h y d r o d y n a m i c i n s t a b i l i t y of t h e leeward  have  flow.  is caused  t h i s view. by  Some experimental  a  basic  results,  5  s u c h as the  direction  blowing, substantiate It  appears  A hydrodynamic to  an  this  that  these  two of  in  the  side force  the  hypotheses  the  boundary  gradients  of  leeward  layer  strength  of  streamwise  of  Morrison  vortices  photography wake  and  behind  and vortex  shedding from  useful data on the  The  with  a 2,  results  however, postulated switching  4, o r  [4]  were  that of  the  pattern  could  an  F-5  the  was  aircraft  h i g h a n g l e s of  ogive  the  that  side  quite  make  sensitive the  the  spacing, They  high  boundary  concern  position  used  the flow  was  nose or  by  two  a  a  mostly  and  schlieren  field in in  the  have  the drag  presented  one. in laminar flow  a pair  of  as it  exhibited  the  by  with  L/D  Reynolds  repeatability. clear  be  = 2.  number, It  was  evidence  A change  in  of  the  roll  unsteadiness. designed  disrupting  symmetrical its  the  of  configurations.  tested  His results  n o s e - c o n e of  lack  properly  force  a  dependence on  demonstrate  model a n d  attack.  may  to i n v e s t i g a t e  unsteady  between  He i n s t a l l e d  be  Their pressure tapped cylinder could  plagued  suggested  stabilize  mechanism. of  [5]  normal  exclusive.  Conversely,  u p to a M a c h N u m b e r of  a clear  angle was u s e d to f u r t h e r Rao  mutually  could  cylinders.  Their  6 calibre  flow  not  tested a slender cylinder  demonstrated  they  of  flow.  studied  slender  different nose geometries.  fitted  effects  the cylindrical body, and they  subject  Lamont and Hunt four  [3]  model.  flow  direction  and yawmeter traverses  a cone-cylinder  are  upstream.  l a y e r separation sensitive to the external Thompson  and  concept.  instability  asymmetric  pressure  switching  static  showed  boundary the  vortex  helical trips and  better  layer  dynamic  on  trip  feeding the  nose  response  response in  all  at  flight  6 conditions except stability.  The  sideslip where the trips  trips, however, did not  decreased  disrupt the  the  directional  vortex feeding  mechanism but did keep the separated vortices symmetrical throughout a much larger flight envelope. Oberkampf and cylinder  in a  Bartel [14] studied the wake of an ogive nosed  supersonic flow.  Although  they  demonstrated  some  interesting characteristics of the wake, the investigation was confined to symmetric flows at relatively low incidence. Ericsson and field.  Reding have contributed rather extensively to the  Their best known papers [1,6,7,15] are reviews of the existing  literature, and critical analysis of the results with conclusions based upon both the previous work and their own. [6] focuses on  the  vortices created by  alleviating the side force.  In particular, reference  the  nose and  methods of  It suggests the usefulness of nose bluntness,  nose-boom, and various geometries of boundary layer trips, in reducing the side force and  presents results showing the effectiveness of the  trips with an F - l l l aircraft model. They concluded that nose bluntness and nose-boom can alleviate the side force to various degrees. other  hand, trips  and  strakes, although  more  effective,  On the have  a  disadvantage for an aircraft not flying coordinated maneuvers. Further evidence of the leeside flow instability hypothesis presented  by  Oberkampf,  Owen  and  Shivananda  [16]  was  in  their  investigation of high subsonic flow past a pointed slender body.  They  used a Laser Doppler Velocimeter (LDV), force and moment measurements, surface  hot  experiments.  wires  and  laser  vapour  screen  photography  in their  The results clearly showed that more than one asymmetric  7 vortex roll  wake  configuration  paper  by  moving wall effects. side  force  Reynolds clear  for  and  Mach  dependence  the  The  study  the  vortex  coning  same  showed  a  shedding  angle  of  attack  and  a  utilizing  demonstrated force,  upstream  or  step  concentrated  spin, coning and The force  the  side  a  critical  coupling  were force  the  pressure  Johnson  [8]  conducted  of  also on  the  on  rate on  the  varying  the  discussed.  the  Reynolds  between  that  pitch  effects  side  within  with the  freedom  on  that  a  the  A  body  motion  number  range.  coning  distribution  the  digital  cone  means  of  amount  the  of  on  a  blowing  one  Lorincz  motion  and  increased  completed  simulation of  a  tangent the  the  initial  the  and  orientation  nose  could  works  LDV,  the  buried Besides  asymmetry,  the  better  of  they  the  nose.  side  It  was  reverse  the  either  the  than  blowing. the  formation  concept  of a c t i v e  experimental from  an  spin recovery  with tangential  aircraft  an  ogive.  c l o s e to  the  combined  automatic  tests  of  carried  vortex  developing an tunnel  side  with  measurements  quite  blowing  [9]  studies  16°  controlling  tangential  asymmetric  wind  and  normal  downstream  They  pressure  mechanisms triggering  Moore a n d  aim of  5°  blowing  that  control  r e s u l t s of  Visualization,  a small  further. to  and  novel  and  Skow,  study  such  upon the  proposed  force  the  d i r e c t i o n of  positive  Screen  instruments  conjecturing also  on  [15]  rate.  Vapour  wire  of  Reding  analyzed.  particularly  Peake, Owen Laser  were  the  and  influence  numbers  of  demonstrated  Ericsson  The  phenomenon  was  a  exist  angle. Another  side  can  performance  and  analytical  aircraft  forebody  system.  blowing was  blowing  a  From  six d e g r e e  developed  to  the of  show  8  that  the  concept  fighters.  They  angles  attack  of  through  the  could  also  of  tunnel  a  fighter  the  asymmetric  and  flowfield  were  a  yawing  plagued  at  the  spin  amount  of  moment  than  recovery  blowing that  at  of high  obtained  with  of the the  with  hence their  repeatability  trips  tunnel  and  helical  trips  on  a  wind  significantly  a large  decrease  noted.  conducted  remaining  helical  sideslip, however,  local side force o c c u r s  side  of  water  designed  zero  associated  effects  Their  was also  [17]  the  F-5.  properly  stability  structures  the  researchers, in  small  studied  the  loads  Wardlaw  maximum  is t o w a r d s  a  more  aircraft,  concluded that  Yanta  that the  produce  L o r i n c z [10]  in lateral-directional  the  that  improve  rudder.  tests  reduced  showed  can  Erickson and model  substantially  some  slender as the  vortex. problems,  observations  fundamental bodies.  first  research It  vortex  was  the  also  many  can only  faced  found  is s h e d ,  Unfortunately by  be c o n s i d e r e d  on  and  results other  qualitative  nature. Almosnino and  circular  trips  on a  in r e d u c i n g the alleviate  the  speeds.  It  slender  side  side was  R o m [18]  force  force  cone wind  at  Mach  tunnel  body. but  Fisher  and  numbers and  They  the  became  concluded that  p r o c e d u r e to implement Peake,  experimented  numerical  [19] 1.5  large  at  studied 1.8  experiments.  in  the  blowing  devices  required transonic  blowing  and future  and  both  rate  symmetrical  McRae 0.6,  found  blowing  very  in existing  of  with symmetrical  to  and  effective  significantly  and  supersonic  is a simple a n d  easy  aircraft. separated flight, They  as  flow  behind  well  found  a  as  a  5*  through  reasonable  9 agreement between the three sets of results, however, the  experiments  avoided test angles of attack which might produce an asymmetric flow. Lamont  [20]  contributed  an  important to the understanding  article  of the  which  has  side force  proven  very  phenomenon.  conducted wind tunnel tests with an extensively instrumented  He ogive-  cylinder in laminar, transition and turbulent separation conditions.  The  results clearly demonstrated a need to vary roll angle in any series of comprehensive  tests.  He  conjectured  that  microscopic  surface  asymmetries at the apex of the body were sufficient to trigger large scale flow asymmetries further downstream. Keener et al. [21] further substantiated Lamont's thoughts on the cause of the side force onset.  His experiments involved measuring the  side force while first rolling his entire model and then rolling the tip alone.  The results,  nearly identical in the  two  tests, support  the  microasymmetry hypothesis. Woolard [22] used a conformal mapping technique to add weight to the  hydrodynamic  postulated  that  instability  boundary  argument.  layer  effects,  Some associated  separation points, cause vortex asymmetry. forebody  vortices  to  the  slender  wing  researchers with  have  asymmetric  Others, by comparing the vortices,  postulate  a  hydrodynamic instability resulting from the crowding of vortex lines at the  apex  comparing  despite cone  symmetric  side  force  separation. onset  angles,  Woolard,  by  successfully  through  the  appropriate  mappings, to slender delta wing experimental data, concluded that the separation lines are unimportant in relation to the basic hydrodynamic instability.  10 Apart  from  previously, slender  other  flow  elements  to  at  theory,  angles  Newsome  20°  found  Chan slender trailing  [26]  body.  only  a  an  45°  roll.  Cyber  using  real  symmetrical  to a s y m m e t r i c for  a  flows  realistic  body.  Reynolds-averaged body  dominated They  used  Excellent  missile.  flow  at  a high  10°  speed  agreement  was  results.  field  approach  modeled the  and  to  study  the  side  far  field  wake  by  established  structure  filaments  were  dynamics of  the  system.  The  showed  205.  around  vortex-lattice  elliptical  and  the  preditions  about  mentioned  R o m [23]  and  the  with 0°  of  numerical  solved  vortex  the  airflow  lines on the  the  numerically  and  the  needed  for  far  of  model  obtained  filaments,  distribution  have  flow  the  [19]  source  input  separation  [25]  experimental  He  vortex  strength  The  for  al.  s u c c e s s f u l l y modeled  attack.  Adams  used  of  computer  the  et  Almosnino and  combination  body,  computer,  with their  modeling  this  attack  vector-processor  Peak  extended  were  a n g l e s of  of  computer  a  the  equations  results  work  been attempted.  location of  and  Navier-Stokes Numerical  of  the  of  with  represent  modeling was  force  also  A l m o s n i n o [24]  higher  and  numerical  avenues  bodies have  potential  flows.  the  of  derived  relationship  the  wake.  from  procedure excellent  a  The  experimental  appears  quite  correlation  with  force on a system  a of  between  the  geometry  and  data  and  the  promising as  the  the  experimental  results. In were  review  proposed  maximum on  the  one  side side  which  force of  article  a  were  occurs body  by  Reding and supported  when  and  a  a  Ericsson by  the  Bubcritical  supercritical  [7] new  three  evidence:  separation  separation  hypotheses  is  the  experienced  appears  on  the  11  other;  the  body  motion  can  lock  produce  a self-induced rotation;  cylinder  when  In vortex some  a  paper  interesting  results.  number  motion  force.  is  Hence  it  Seginer attack the  effects,  angle  pitch The  regardless  Ringel the  is  of  He  In  occur  to a  the  drives the  angles  to was  the  separation,  body  paper  body into  and  [11]  over  present  tip  the  critical  at  determines  of  the  the  such  that  static  side  induces  range.  due  to  asymmetric  at  It  the  high  was  angles  observed  boundary  layer  contribution.  interdependence  of  the  Their  spin  rate,  and  their  lift. spin  of  types its on  Blender of  the  a flat  bodies  separation  attendant  lift  and  subject  [29]  asymmetric  possible, the he  the  Magnus shows  vortex  pattern,  a  cone  spin.  conducted a  and  [1]  Magnus effect  motion l o c k s in an  Narayan  47*  flat  depth  recent  slender and  information  on  more  Viswanath up  in  the  motion  sheds vortices  classical Magnus  and  a  asymmetry.  when,  complex  explored  that the  static  on  Reding  spin  motion  number  motion  a  vehicle  Reynolds  can  the  to  flow.  body  direction  critical  discusses  body  the  the  opposite  [28]  of  explored  reversal  of  and  action  of  can occur  a turbulent  spinning  [27]  demonstrated  conclusively which  coning  of a t t a c k , R e y n o l d s n u m b e r  recovery.  effect.  The  a  asymmetry  separation  Ericsson  direction  any  Ericsson  effect  the  easily overpower  lift  experiments  that  vortex  coupling  with  the  in  the  earlier,  that  force the  on  Tests  appears  and  and  to  force.  sustained  vortices which  that  side  driving  nose is experiencing  showed  the  a  and a laminar  concentrating referred  d i r e c t i o n of  of  pointed  shedding  Reynolds  the  the  in  wide  range  c o n f i n e d o n l y to the  force  tests of  with  the  balance  20"  Reynolds data.  at  number.  12  M o d i et which  a  effects tip  set of  al. of  boom a n d  Bishop, flow  tip  had  flow  inclined  cone.  first  produce capable from  methods,  the  the  Marconi for  supersonic vorticity boundary  flow  positions.  second family  [31]  has  regime,  layer.  of  a  also  using the  Solutions  an  core  locations  field  obtained  the  of  several  flow two  past  of  lines  solutions  even  using  when  are  the  vortex  results  to  fed  to  manipulations  numerical  an  categories.  contribution  scheme  delta-  sheet which  compared  data.  past  Euler  flow  own  The  subsonic  separation  family  by  reduction.  for  second  contributed  flows  tried,  into  parametric  results.  in  summary  results  His  and  nose-  report  cone  side force  models  numerical  experimental  vortical  studied:  of  28'  asymmetric  vortex  formulae  with the  sheet  The  asymmetric  development  highly  are  results.  a  excellent  require  and  the  project  geometries  of the  numerical  the  geometries  devices tested,  on  nose  an  explored  to  promising.  tests  vortex  solutions  clever  favourably  results,  of  tip  engineering  [13],  various  They  modified  most  year  the  attached.  trips,  be the  and  with a circular cylinder  alleviation  presented  separation  some  produced  the  divides  producing  was  to  fourth  vortex  He  symmetric  problem  quite  line  asymmetric of  be  most promise in terms has  family  force  proved  among  the  can  Thornthwaite  [30]  potential  The  and  that,  Fiddes  experiments  helical  side  unpublished  Tarnai,  tip  the  rotation  an  out  roughness,  Among  indicate  strake  carried  conical forebodies  surface  rotation.  In  [12]  some  cones  equation shock with  interesting  and  delta  model.  both  the  wings  Two  system; and  numerical in  sources  the  s o u r c e s of  the of  separating vorticity  13  are  s t u d i e d i n detail, a n d c o m p a r e d  with  flow c a l c u l a t i o n s a n d t h e experimental It i s a p p a r e n t experienced attention  data.  the literature that the problem  b y high performance aerospace  relatively  understanding  the side  recently.  Some  of s i d e f o r c e  vehicles has r e c e i v e d active  progress  has  been  made i n  of t h e p h e n o m e n o n a t a f u n d a m e n t a l l e v e l a n d t h e r e a r e  several hypotheses of  from  e a c h other, with t h e p o t e n t i a l  w h i c h seem t o e x p l a i n some a s p e c t s of t h e mechanism  force  generation.  On  the other  results are often not reproducible, suggesting  hand,  the experimental  t h a t t h e models u s e d i n  e x p l a i n i n g t h e p h e n o m e n o n are, a t best, incomplete.  1.3  E.urpQ.s.e._.an.d__S.cope. o l ...the I n v e s t i g a t i o n With  precise  this  as  background,  information,  obtained  the thesis  through  a  aims  at  s e t of  providing  carefully  experiments, a s s u r i n g r e p e a t a b l e a n d r e l i a b l e data, to b e t t e r the  s i d e f o r c e phenomenon.  field  associated  with  a  It aims  slender  cone  at s t u d y i n g and  several t i p devices i n alleviating the side force. review  t h e flow  field  v o r t e x dominated is somewhat problem itself  experimental  b y the Reynolds  angle  to the known  investigation,  boundary  As apparent  layer  of a t t a c k  analytical  therefore, program.  a n d Mach  forebody  o r numerical  purely  relies  from the  Furthermore, i t  numbers.  procedures. a  flow  sensitive, turbulent,  aerodynamics  on  understand  e f f e c t i v e n e s s of  a n d h i g h l y c o n f i g u r a t i o n dependent.  affected  of h i g h  i s unsteady,  planned  t h e asymmetric  assessing  more  Hence, t h e  does The  carefully  not lend present planned  14  Several booms,  strakes,  success cases  as  to  the  mostly  trips  their  tests  problems  which  purposely  be  It  to  The  criterion  house  uniform,  particular which  directionally. devices  as  nature  prime  nose-  degrees In  with  of  most  results  its  success.  well.  degrade  particular  device  forms  required the  radar  is  are to  prove  nose  composite its be  of shell  as  Water  the  other  attention in this  porous  hand,  devices  only  thesis.  or  a missile  which  the  no  is  appear  aircraft,  to is  moving  transmission as  possible,  considerations, and  is  alleviation  with  a  performance  being on  such  uniform  absorption  make  aspect  impractical  spectral  performance  to  radar  may  situation  force  devices  is  practical.  this  focus  aircraft  class  devices  real-life  side  the  the  likely  On  the  of  force  nonmetallic  the  this  emphasis  be more  in  nose of a n some  side  which  of  The  Although  concern here,  radar,  to  for  passive  force.  deemed  performance  a  several  side  the  impractical.  microwaves  strakes  received  from  appear  unsuitable  tried  force.  foundation  with  of  importance  are  Hence,  of  of  the  radome,  thin,  side  in  a firm  study  applicability  alleviating  characteristics,  have  to l a y  recognized that as the  Of  booms a n d  in  on  is  implement.  the  is  have  varying  the  preliminary  systematic  information  in  device  a  the  promising  attenuation  attempts  not  used  moving  study  ultimate  frequently  parts.  rather  are  it  with  reducing  on passive devices as they  fundamental  a  in  the  of i m p o r t a n c e ,  usually  roughness  reducing  the  devices.  [5,6,9,12,13,18]  character.  promising  Obviously, would  past  surface  been  through  appear  the  effectiveness  in  present  in  and  have  qualitative The  of  investigators  its tip such  marginally  active  attendant alleviation as  nose-  and  hence  15  M O D E L S AND  2  This chapter experiments, The  briefly  test  wind  aerodynamics laboratory test  procedures  instruments  2.1  describes the  arrangement,  conventional  are  tunnel  well  PROCEDURES  models used in  instrumentation  needs  also  TEST  equipment  no  and  being  explanation.  established.  the wind test  Only  with specific role are touched upon  procedures.  standard  Most of  tunnel  in  any  the wind  distinctive  tunnel  models  and  here.  Cone - M o d e l For  the  diameter and  entire  10 c m l o n g , w i t h  model.  The hollow  cm  in.)  (6  experimental  long  accommodated  aluminum and  up  to  had  40  program  a  cylindrical  a conical forebody  formed  cone with an apex angle a  base  pressure  diameter  taps.  of  The  base,  of *  7.62  apex  of  the  7  cm  basic  28" w a s  cm  (3  the  cone  test 15.25  in.).  geometries.  cylindrical aft  to rotate the  at  a  controlled  h o u s e d a v a r i a b l e speed d.c.  speed  during  one  phase  The aftbody  was also c o n n e c t e d to a y o k e  mounted  the  on  tunnel  attack  and  though  modified and refined,  B i s h o p et the  yaw  wind  inclination  a l . [13].  Figures  balance can  be  of  model and its exploded view,  and  2-2  show  respectively.  experimental  such  as  that  required.  same as the the  test  the  be The tip  program.  vertical support,  platform,  is essentially the 2-1  the  type  adjusted  motor  It  can  s e p a r a t e d at two locations to r e p l a c e it w i t h d e s i r e d t i p body  in  in  turn  angle  The  of  model,  one u s e d  arrangement  by for  16  Figure 2-2  An exploded view of the cone-model.  17 The  pressure  modification, its  length.  surface  In  as  carrying with  were  16  a  indicated  with  pressure  taps, roll  pressure  at  a  on  minimize  side  finish.  the  With  was  the and  the  2-4)  0.64  housing  bearing  inside  diameter,  of  surface  to  of  an  cone  replaced  (Figure  2-6)  with  the  be tested  mode. is  cone  the  and  tip  along  on the  c a n now  diameter,  no  stations  housing,  spinning  in  with  apex  bearing  the  mm  six  removed  nose-tips, which in  i.e.  be  The  as  at  brass  can  a  taps.  well  mm  effect hence  the  to  was the  the  better  cone  exception  polished  roughness  The  static  conveyed  externally  at  by  a  located  model  of  within  identify  a  some 5-7  of  the  higher  model may  the  smaller surface at  on  influence  provided  micron  necessarily  cone, the  was  roughness  with  the  of a  nose  boundary  tip  geometry  smooth tips,  the  roughness.  junctions  of  mirror entire  Although  the  various  be c o n s i d e r e d essentially  smooth.  T i p .Gjeoinetries The  standard employed, the  1.7  force,  components of  2.2  as  model,  distributed  The  or  different  typically  tube,  instability,  the  cone  tap,  2-3.  2-5)  pressure  supports  pressure taps  (Figure  (Figure  cone  circumferentially  Figure  taps  three  standard  transducer.  To layer  w e r e 40  orientations,  polyethylene pressure  tip  the  spaced  in  pressure  provided  for  equally  all t h e r e  porous  desired  taps  test program tip  shown  which  side force  can  in be  made Figure  use of 2-3,  rotated  dependence on the  several a  about  tip  smaller its  roll angle.  geometries.  tip  axis  (Figure quite  Besides 2-7)  readily  was to  the also  assess  As discussed in Chapter  1,  15.25SECTION A-A  CONE MODEL WITH STANDARD TIP  RING OF 3  'I 3.18^—4.32 -5.59 BEARING HOUSING WITH ROTATABLE STANDARD TIP  Figure 2-3 A section view of the cone model  ( a l l dimensions i n centimeters)  %  19  Figure 2-5  The porous cone tip.  Figure 2-7  A family of nose-boom tips with the standard tip shown for comparison.  21  L a m o n t [20] the  and  K e e n e r e t a l . [21]  did  dependence  of  side force. The tests have focused primarily  nose-boom review The  observe such roll  (Figure  2-7)  and  suggests both the  nose-boom  lengths  0.16 c m ( a s p e c t r a t i o 46 a n d  delta  strake  used in  variation  the  based on  The length  observed  a  loss  of  the  2-8).  varied  the maximum  of the 1.  literature  [5,6,8,9,12,13]. from  2.7  cm  boom d i a m e t e r  delta strake  to was  varied from  As several earlier  lateral-directional  geometries:  The  side force  experiments  c m t o 0.32 c m w i t h a n a s p e c t r a t i o o f have  (Figure  d e v i c e s to affect  2, r e s p e c t i v e l y ) .  [5,6,8,9]  o n two families of t i p  3.2  investigators  stability  with  the  d e l t a - s t r a k e , t h e t e s t s w e r e a l s o c o n d u c t e d at y a w a n g l e s of ± 10".  2.3  Tunnel  Wind  The cone model was tested in type  wind  tunnel  with a turbulence the  contraction  where  the  air  a low  of  7:1  The  ratio 0.2  velocity  above  rectangular 45"  corner  partly tunnel  calibrated  against  c r o s s - s e c t i o n , 91 fillets  which  vary  compensate for the outline.  the cm  from  wide  be of  mm  X  15 cm  turbulence from  return  1 to  46  pressure differential  can  micromanometer w i t h a n a c c u r a c y of is  low  s p e e d c a n be v a r i e d  l e v e l l e s s t h a n 0.1%. section  speed,  measured water.  pressure 69  cm  boundary layer growth.  to  across a  The test  Betz  section  differential.  high, is  X 15 cm  on  m/s  The  provided  12 cm  X  12  with cm  F i g u r e 2-9 shows  to the  22  Figure  2-9  A schematic wind  tunnel  diagram used in  of  the  the  low  speed  experiments.  23  2.4  Instmmentetiojni Although  the  model  was mounted  turntable. to  a n y desired  incorporates orthagonal  it  an  (pitch,  microvolt  was used only  are  purposely The  model  used,  Datametrics high  with  relatively readings diagram the held  measurements,  Aerolab  supply  balance  the turntable  c a n be  adjusted  gauge  balance  T h e strain  cells  which  force  a n d yaw) in  provide  (lift, d r a g  conjunction  Due to excessive indicator  a n d side  with  drift  the  three force),  a  Leeds a n d  of the  instrument,  a n d hence the balance  h a d 24, 27, o r 40 p r e s s u r e scanivalve  type  48J9  connected  the  Barocel  Pressure  Sensor,  Betz  stable,  capacitive  u p to  were  ±  10  mmHg  tachometer.  (Figure  results  taps  As  voltage  divider  mmHg.  T h e resulting  and for off to  the rate  the  reasons  of  the nearest  set-up  which  type  1018B  mmHg.  calibration  the A  in Figure  was measured  2-  Manometer  fluctuations  convenience,  a  was  (Figure  to be in  stream  is presented  of rotation  voltage  a  is a  measures  a n d Electric  0.01  to  T h e Barocel  was found free  device  sequentially  511J-10.  Barocel  upon thetip  2-10) switching  type  a n d the system  of the instrumentation tip tests  depending  Electronic Manometer,  Manometer.  rounded  taps  pressure  of the combined  insignificant  Shimpo  load  of the resultant  to a Datametrics  spinning  built  attack.  which  i s 0.001  the  of  six  amplifier.  The accuracy  system  custom  the model,  angle of  roll  pressure  transmitted .  a  a s a qualitative  A  precision,  differential  11)  on  was in the pressure  not reported.  configuration. was  array  components  moment  Northrup  interest  Besides supporting  provide  and  the primary  were Barocel  schematic 2-12. F o r  with  a  hand  24  Figure  2-11  The Barocel pressure transducer electronic manometer.  and  25  Electronic Manometer  Figure  2.5  Instrumentation layout for pressure measurement using a Scanivalve and Transducer.  stronger caused  the  with a similar  model s u p p o r t a s it  by  of attack.  highly  turbulent  Preliminary  o n s e t of v i b r a t i o n  25.8  m/s.  22.7  entire  Hence, for  m/s which range  tests to  the  the  used  by  the  comparison of  cone earlier  the  was f o u n d separated with the  present test  T h i s is more  data.  The  diameter  Barocel  is  had indicated a need be s u s c e p t i b l e to  flow  at  higher  improved free  program  stream the  eliminated than  speeds and  support  is  1.1  in  the  X  wind  system  delayed  speed was  vibration  s  which  [1,4,11,20]  over  speed  range  where  compares  and the  hence  a  angles  speed as h i g h  double the  10 ,  for  vibrations  as set  the  previously  corresponding Reynolds number  investigators It  to  with the  (with one exception)  of interest.  maximum  m o d e l [13]  a > 50*  achieved without vibration. on  a  Test Procedures Earlier tests  at  2-12  based  with  that  facilitates  Reynolds  number  26  dependency higher  is  negligible  Reynolds  separation  may  exhibit  and  separation.  higher  number still  may  a  In  results  from  The  the  the  is  3  2  been  been less  the  repeatability  10  by  of  laminar. X  on  10 , the  and  laminar  other  side  number  much  as pointed  repeatable.  here  a  reattachment  Reynolds however,  At  a  6  turbulent  the  problem roll  flow  a  predictable  -  5  the  reported,  that associated with the steps during  X  while  range  have  series of  separation  followed  critical have  of  side  separation this  flow  range  on one  side force  be emphasized that in origin  in  occur  laminar  l e v e l s of  before, the  and  It  is distinctly  out  should different  orientation.  a typical  test  may  be  summarized  as  follows: i)  set the  balance table  i i)  set the  yaw  iii)  set the  nose tip  iv)  set the  tunnel  v)  read the  vi)  electronic  increase the  series  the  repeatable  of  tests,  measurements During the  whole  character the  were limited the  For  to the  required  rotated the  the  taps  0;  speed;  with the  Scanivalve  and  manometer; of attack  tunnel of  the  a by  s p e e d if data  procedure  up  to  established  was  shortened  through and  a the  50*.  effects  tips  50',  needed.  its axis as the  spinable  10*  was  40°, and  roll angle  about  smaller  roll angle  to a p r e s e l e c t e d wind  to a = 30",  assessment of  model was  independently.  above  0;  desired;  angle  the  a =  (3 a s  p r e s s u r e s at  resetting Once  angle  to  with tip  only  the  standard  could not  the  tip  be  tip,  rolled  position  was  27  changed. the  T h i s is  expected  rolling of the The  entire  dynamic  readings  being  obtained  directly,  head  to  give  results  body as shown =  (1/2)pVt  from  each  q  available  2  similar  by and  tap,  a  to t h o s e o b t a i n e d  Keener et  al.  individual pressure  with  [21].  Pi  -  P*  coefficient  pressure can  be  surface  to  Cpi - (Pi - Pm)/q. The  pressure  obtain  the  Appendix  coefficients  force I.  were  coefficients.  integrated  The  over  integration  the  routine  cone is  summarized  in  28 3  The the  amount  system  is  of information  parameters  angles; tip etc.,  R E S U L T S fc D I S C U S S I O N S  rotation;  rather  presentation  such  as  the  s c a n n i n g o f 40  extensive.  of  obtained  data.  There  An  effort  through  tip  a planned  geometry;  roll,  pressure taps  are is  several  made  and  convey  standard  cone-tip  reference  to  with  nose-boom, delta-strake  the  effect  of  the  experiments through  assess  data  effectiveness  tip  with  rotation  is  repeatable  adjustment  of  are of  presented  other  and  porous  evaluated.  results,  the  tip  the  tip  first,  geometry  pitch  integration; for  which  as  serve  The  tip  Finally,  follow.  carefully  side  are  the  information  geometries.  at  of  trends.  Such  aimed  and  available  concisely as possible with an emphasis on discernable The  yaw  their  options  to  variation  force  not  as  results the  planned alleviation  reported  in  the  ratio  was  different  roll  literature.  3.1  SfcftiJicliftr d J C o n e . J I i p _ ^ o l I _ j £ 3 . t s . The  tested  in the  positions. and  plain  range  The  integrated  normal  force  patterns direction, hand,  the i.e.  large  cone  tip  (Figure  the  cone  both  pressure  distribution  from  nose  the  pressure  variations  direction especially for  the  pressure  any  at  to  the  length O to  50°  each pressure  surface  For  4:1  from  coefficient at  components.  variation  of  of a n g l e of attack  pressure over  2-4)  to  evaluate  symmetric  varied base  were  asymmetric particular  only of  flow axial  radius  in  12  tap the  and  was side  cone. in  station  in On  the  situations.  calculated force  asymmetric  slightly  the  noticed  to  the the  and flow axial other  circumferential Thus,  can  a  serve  plot  of  as  a  29 qualitative 25.3%  of  largest  pressure  the  total  number  Figure the  lift  range  a  = P  0  is  asymmetry force.  roll  appears  of  respect layer  attack to  =40°  300°,  F o r the  zero  in  the  is  this  angle  axial  end  station  as  it  P  had  about  the  suggesting  now  the  direction  angle).  net  governed  by  is  In  attack.  Note,  of  at the  vertical  presence  pressure  side  force the  tip  is  suggesting  of  in  at  a  the The  net  the  any as  the  plane.  side force  surface  in  side  distribution  understandable  the  general  distribution  axial  the  without  This  roll angle.  pressure  twelve roll positions tested  roll  instability  plot for  similar asymmetric  but  changed  the  to  Cp  symmetric a  The  selected  circumferential  shows a  of  cone.  taps.  increase  the  at  3-2  angle  direction. angle  30*,  entire  was  typical  an  essentially  Figure  a  with  the  length  shows a  -  for  pressure  increases  station  for  cone  of  3-1  loading  case,  opposite  at  a  given  trend  (with  the  boundary  roughness,  a  random  parameter. Figure positions. close  to  It  3-3  presents  clearly  30°.  This  21].  randomly affected,  is  by  the  It  is  as  explained  surface  instrumentation Figure  due  large  that  to  the  the  at  shows  the  Note  Its  the  the  of  value  force  12  force the  for  [1-5,  a in  different starting  cone  changes  This would  15,  direction  the  require  at  angle  11, 12,  given  roll  a  more  and 17,  rather is  flow,  a  also  induced extensive  accurately.  force  results  of  asymmetry  field  normal  side  magnitude  tip.  flow  in  for  investigators  side  extent  to a n a l y s e the  twelve roll positions.  the  before.  variation  increase  r e s u l t s of o t h e r  roughness  3-4  force  approximately  apparent  perhaps  side  shows a  compares well with the 20,  the  coefficient  show a marked  variation scatter,  at  for a  the  a, deg. o A + = X = o = V = 360.0  Figure 3-1  Pressure distribution at a reference station P, as affected by the angle of attack, for the standard tip at zero roll angle.  0 10 20 30 40 50  '  0.0  i  60.0  I  120.0  1  1  1  180.0  240.0  300.0  !  360.0  e, d e g . Figure 3-2 Pressure distribution at a reference station P, as affected by the angle of attack, for the standard tip at a roll angle of 300*.  0.0  10.0  20.0  30.0  40.0  50.0  60.0  a, deg. Figure 3-4 Variation of the normal force coefficient for the standard tip model with pitch and roll.  34 given can  a, s i g n i f i c a n t l y be  explained  Although the  by  density.  show  force  was  taps  results  conducted different eliminated  with the  a  best  variations attributed The  visible.  of  to  the  shows  two  asymmetry switches  fluctuations  30° a  in  observed  while most of  with  roll  same  Now  can  pressure  second  tip  induced  and  pressure  the  ring  the  subsequent  the  angle.  repeatable  of  positions). All  This  cone surface  the  alone  of  normal  tests  were  rotated  experimental  of  negative  force  side  procedure  the  tip  force  force  pressure  a  error  the  Note,  biasing of the  The had  result  pointed profile  to is  fact  although  entirely  model  was  its  out  be  before.  strikingly pattern  Figure  3-5 large  the  side  force  rolled  true  may  any  due  spacing.  minor  of  (Figure  is  about  the  type  that  roll  obtained  is  wave  constant  a 60°  the  were  Note,  probability  coefficient  taps  as  The  by  coefficient  square  [20].  is nearly  error.  tip.  surface  follows  Lamont  affected  results  the  construction.  normal  These nose  discounts  integration the  of  by  waves  normal  50°.  as  symmetric  variation  model  the  are  the  only  variation  integration  one  the  of  nearly  force  pressure  positive or  and  side  direction  the  orientation  12  roll  force  incidence  pressure  the  3-2  over  scatter.  the  side  magnitude  square in  and  the  position,  microasymmetry  The  similar  induced  the  the  pitch  the  to  effect  roll  with  c o v e r e d with the  through less  side force.  tests.  polished  in  3-1  integrating  Thus  shows  fixed  upon  by  distinctly  body  in f u r t h e r  position at  Figures  rolled  positions.  3-5  of  the  variations  pressure integration  taps  one  Figure  field  depending  showed  roll  flow  checked  (12  at  that observed for  cone model is not  variation  This  pressure  the  than  plots  Hence, the  some  taps.  the  pressure  e a s y to i n t e g r a t e , tap  larger  3-6). to in  the  The roll  steps  of  This results  in  value.  0.0  60.0  120.0  180.0  240.0  300.0  360.0  0, d e g . Figure 3-5  Effect of the standard tip roll position on the side force at a pitch angle of 50".  Figure 3-6  Effect of the standard tip roll position on the normal force.  37 The was  maximum  1.22.  This  coefficient reference  (1.5).  may  coefficient  the  This  be  order  well  coefficient  of magnitude  value  of  et  C s t o b e 1.25, w h i l e  side tip  nominal  that  Keener  the  of o t h e r  this  with  for the  Viswanath  as the normal  force  force  as  value  in  tip  is  used  a  geometries.  obtained  a l . [21]  standard  of  by  the  side  several  earlier  his experiments  and Narayan  [11]  force  with  a  obtained  = 1.10 f o r a s i m i l a r c o n e m o d e l .  NQs.e-.Bpom T e a t s Each  darning  nose-boom  needle.  was  A family  (Lb)  from  0.16  cm) was u s e d i n this  4.13 c m t o 0.16  Each In  these  As  pointed  same  test  tests  effect  just  a  of  3-7(a)  and the  of attack  different  mm  needles,  3.18, 2.54,  was rolled et  shows roll  longest  dependence on the tip  0.89  diameter varying  tapered in  length  1.91, 1.27, 0 . 9 5 , 0 . 6 4 , 0 . 3 2 ,  nose-boom was carried  al.  obtained  nose  (the  nine  a  test-program.  Keener  that  from  c m (4.13,  did substantiate  nose-boom  angles  made  the tip  by  as  Figure incidence  with  out  experiments  tip.  force  out that  F o r example,  cone found  3.2  cm  same  nominal  pointed  compares  researchers.  Cs  is of  side  to a s s e s s t h e e f f e c t i v e n e s s  It  20°  recorded  instead  [26], t h i s by  observation.  the  side  used  force  in  roll orientation  the  of t h e entire  the  this  when  the  tip  cone  > 3 0 ° ) , similar  to  with  is fitted  T h e magnitude  of t h e maximum  side force  the  with  d i d show a  The  the with A  be p r e s e n t  observed  body.  model.  test-program).  (a  positions.  to produce  entire  variation  continues to that  six roll  is expected  rolling  position  out at  the  pitch a  4.13  marked  at  higher  standard  significant  38  F i g u r e 3-7  E f f e c t of boom l e n g t h o n v a r i a t i o n  i n the  s i d e f o r c e c o e f f i c i e n t with p i t c h a n d r o l l (a),(b),(c).  attitudes:  39 (50%) r e d u c t i o n . did  result  coefficient  3-7(b)  a  showed  to  an  this  set of tests,  side-force  3-7(i)  show  in the  similar  increase  in  force  side  Cs.  the largest  nose-boom  reduction. variations  nose-booms tested.  reduction  direction of the side roll  during  for the other  showed  cm  fact  i n t h e maximum  Figures  cm  In  force It  is  is dependent  in  the side  T h e booms l a r g e r while  of  those  smaller  interest  on both  to  force  than  0.95  than  0.95  note  that  the pitch angle  the  a n d the  orientation. In  general, the changes in magnitude  d i r e c t i o n , w i t h a a n d 0, w e r e l a r g e r  for  accompanying the changes in  shorter  boom-lengths  (Lb  < 0.95  cm). It  is important  for  a  given  Reynolds the of  to  point  model  at  number,  side force  stream  fixed  repeating  (without  the phenomenon  free  out that  is  even  pitch  and  the test  affecting  roll  well  and  as  the  a  fixed  direction  This bistable  considering its  as  c o n d i t i o n s , i.e.  to a different  its magnitude).  character,  test  orientations,  may lead  understandable  turbulence  for identical  character  sensitivity surface  of  to  the  roughness  distribution. Figure better  percentage  of  the  the  change  length.  defined  the  (Lb/L  boom l e n g t h s  the  effect  of  absolute (from  Although  pattern  boom l e n g t h s longer  summarizes  appreciate  variations  boom  3-8  overall  information  nose-boom  maximum  the the  above  no  and  side  trends  variations are  < 0.7)  tend  there  is a distinct  well  to increase  its  force  nose-boom  local  in a  length.  as not  affected exhibit  established.  the side  reduction  way  It  coefficient  case) do  useful  shows  and  its  by  the  any  The  well  shorter  force, however,  i n t h e maximum  to  Cs.  for It  40  in o  1 0.0  1  1  10.0  20.0  I  30.0  a  f  1  40.0  1 50.0  ' 60.0  deg.  Figure 3-7 Effect of boom length on variation in the side force coefficient with pitch and roll attitudes: (d), (e), (f).  o  Figure  3-7  E f f e c t of side force (g),  (h),  boom l e n g t h coefficient (i).  on variation  in  with pitch and  the roll  attitudes:  Figure  3-8  Magnitude varying case.  of the  maximum  nose-boom  length  side force coefficient including  the  with  standard  tip  43 is possible to achieve a reduction  in maximum side force coefficient by  around 50% through the appropriate  choice of the nose-boom length.  Figure 3-9 shows normal force variations with the pitch angle for the case of a 4.13 cm nose-boom. The  It is nearly linear with little scatter.  normal force plots for the other boom lengths  show similar trends.  Variation of the normal force with the nose-boom Figure  3-10.  It is apparent  that  length  effect of the boom  is shown i n  length  on the  normal force coefficient is relatively small.  3.3  De.lt^„stmke_. Tests Tests  conducted  with  3.18 cm  delta strake  tip shown  at 6 different roll positions.  effect of the strake  in Figure  2-8  were  Of primary interest was the  when perpendicular  to the pitch plane, as this  configuration was expected to be successful at minimizing the side force. However, the tests were also conducted at roll angles of ± 10*, ± 20° and  90°.  flight  The small roll angles would be of interest for noncoordinated  maneuvers, while  effectiveness  i n side  the  force  90°  position  alleviation  was  with  tried the  to compare its  more  conventional  orientations of the strake. Results of the side force variation with pitch and roll attitudes for  the 3.18 cm  delta strake are presented in Figure  3-11.  Note, both  zero and 90° roll orientations of the strake seem to promote symmetric flow fields with the zero position proving  a little better.  For a given  pitch angle, particularly with a > 30°, the presence of a small roll angle (± 10°, ±20°) seems to reduce effectiveness of the strake i n promoting the  flow  symmetry.  However, it is encouraging  that  the side  force  remains relatively low over the entire range of the pitch angle tested.  o  i  0.0  1  1  1  1  1  10.0  20.0  30.0  40.0  50.0  a, deg.  Figure 3-9  Normal force variation with pitch angle and roll orientation for the 4.13 cm nose-boom.  r  60.0  Figure  3-10  Normal force coefficient v a r i a t i o n with pitch incidence and nose-boom length.  deg. 8  -  •o •1  0.0  • =  1  1  1  1  1  10.0  20.0  30.0  40.0  50.0  o  f  Figure 3-11  deg.  Variation of the side force coefficient with pitch and roll angles for the 3.18 cm delta strake.  f  60.0  0 10 10 20 20 90  47 As  several investigators  stability  with  strake  conduct tests condition.  tip,  Figure  3-12.  viewed  by a  clear  side  a  for  10°  =  negative  side  in  3-12(b)  as the  for  B =  ±10°  cone  is  On  show  and  the  the  surface  to  as  is  the  other  sideslip with  pitch  the  trend  in  right  (as  angle  left.  This  hand, pressure  reverse  the  distribution  the  to  to  presented  pressure  However,  direction  zero  are  yawed the  important  normal  cone  of attack,  stability.  deemed  the  right.  reverses  positive  resultant  angle  for  B =  series  of  tests  0°  side  and  it  direction.  easily  the  the  was  lateral-directional  plots  indicating  a  stability.  The  yaw  to  it  loss of  over  pitch  zero angle  load  Figure  the  a  as well  plots  3-12(a)  force  strong  angles  by  At  reported  devices,  distribution  Figure  pilot).  the  yaw  affected  In  suggests B  as  the  increases  alleviation  nonzero  Pressure  standard  shows  at  have  ±10°  seems  It  force  overpowers  (Figure  the  appears  coefficients are  side that  3-13a) f o r force  plotted the  direction  microasymmetry  against  standard is  of  not the  any  inherent  directional  stability  the  pressure  integrated  side  the  tip.  In  affected cone  of  pitch this  by  tip  the  surface  this  forebody  data  for  configuration. Results  for  various lengths through  3-13(g).  apparent note  for  that  the  the  decreases and unstable It 0.32  of  in is  delta  strake  tested  E v i d e n c e of a weak 3.18  cm s t r a k e  stability below  Ls  gets =  tip  are but  force  presented positive  in  directional  (Figure  3-13g).  It  progressively  weaker  as  1.27  cm  point  out  the  model  Figures  becomes  is  of  the  the  3-13(b)  stability  is  interest  to  strake  size  increasingly  more  yaw. important  to  cm showed promise in terms  that  of the  all  the  strake  tips  side force reduction.  larger On  than  the  o= 0 A = 10 + = 20 X = 30 o = 40 V = 50 1  0.0  1  60.0  1  120.0  I  I  180.0  210.0  I  300.0  e, d e g . F i g u r e 3-12  Pressure distribution, a t the reference station P, f o r the s t a n d a r d t i p a t a yaw i n c i d e n c e of: a) B = -10'.  360.0  Figure 3-12  Pressure distribution, at the reference station P, for the standard tip at a yaw incidence of: b) 0 = +10*.  0.0  10.0  20.0  30.0  o., Figure  3-13  Variation of the  40.0  50.0  60.0  deg. Bide  force coefficient  with  pitch and yaw angles as affected b y the delta s t r a k e l e n g t h ( a s p e c t r a t i o =1): ( a ) , ( b ) , ( c ) .  51  d) Ls = 1.27  0.0  1  cm, L s / L - 0.083  I  10.0  i  20.0  30.0  o.  f  Figure  3-13  V a r i a t i o n of t h e pitch and strake  yaw  length  i  1  i  40.0  50.0  60.0  deg.  side force coefficient angles as affected  (aspect ratio  =1):  by  (d),  with the  (e),  delta (f),  (g).  52 whole  they  reduction  performed in  the  nominal value As  does  normal by  pitch  force  to  is  yaw  the  contribution  is  It  strake  = 3.19  the  for  cm  However,  given  a.  the  3.18  cm  3-16  strakes.  was  variation  a  Figure  delta  achieved  linear. at  nose-booms.  increased.  portion  of  the  of  however,  this  a  loss  small  side force obtained  total of  normal  the  the  with these  3-15  the  yaw the  affected force  in the  normal  forebody  a  lift  missile  or  an  have  to  be  would pay  as  normal  the of  to  force  shows  strake  lift  the  p r e s e n c e of  If  lift  penalty  of  of  decrease  is  88% 3-14).  delta  slight  maximum  (Figure  Figure  length  importance  around  summarizes  A  The  for  the  large  tips.  EQrou.s_. T i p . T e s t s The  porous  e q u i p p e d »with The  results  the  Ls  study,  results  of  seems,  reductions in the  3.4  the  significant  the  of  is essentially  the  a  than  strake  angles.  as  then  analysed.  delta  family  noted  aircraft,  coefficient  coefficient  and  for  force  nose-boom  scatter  force  results  the  pitch angle  tend  better  with the  with  with the  side  much  a  perforated  length.  The  reduction standard slightly It  the  value. (6%)  seems  in  comprised  the  test  approximately  side  force  nose-boom  case  and  On  the  other  normal force  logical  that  vortex  formation,  with  20%  a the  49%  of  efficient  0.64 the  was  tip  standard  porous across  as well as negate  tip  its the  2-5) mm  was holes.  total 0.62,  reduction  porous  that with the  pressure  (Figure  coefficient  hand,  than an  of  program  perforated  recorded  communication  symmetric  used  cm n o s e - b o o m , a n d  maximum  higher  instantaneous enhance  3.18  tip  portion  from tip  brass  cone a  38%  from  the  recorded  a  tip. with  surface effects  near would of  Figure 3-14  Effect of the strake length on the magnitude of the side force.  OJ  0.0  10.0  20.0  30.0 ex,  Figure 3-15  40.0  50.0  ,  60.0  deg.  Variation of the normal force coefficient with pitch and yaw angles for a strake of 3.18 cm.  o CM  Ls / L Figure 3-16  Effect of the strake length on the normal force coefficient.  56 asymmetric had  vorticies.  several  The  porous tip  the  tap  size  roughness (ii)  the  is  thus  porous  larger  rather partly  length  internal  (iii)  the  problem  internal  is  established,  experiments  in this  earlier  suggested was  a  local  is  of  the  even  program  the  surface  this  are  the  presenting  average  a  pressure  of  here  the  as  the  cone  and  there.  in  to  thus  base  reducing  preliminary  likely  influence;  accentuated  the  tip  to  value;  pressure  porous  by  direction  to  long, in  further  extends  desired  too  resulting  the  (ii)  preliminary  be  Several  precisely the  spinning the these  in  to  The  and  in  tip  the  test.  side  force  Better  is  planned  fruitful.  and the at  the  direction  For test  c a n be of the  by  Modi  force  when  tests  were  rotation.  Variations 3-17.  side  planned  conducted  of i n t e r e s t  force.  of  tip  used.  Figure  50°  observations i)  effect  were  small D.C. motor  through  carefully  standard  tests  shown  investigation  possible reduction  spun.  more  are  test  S i n n i n g .Jip..Tests The  All  present  contributing  perhaps  communicates with the  3.5  the  cancelling its  from  in  gap  effectiveness  large  volume  that is different  clearly  in  limitations:  (i)  However,  used  et  the  al.  tip  conducted  The first  up  2000  maximum  in  the  each  side  tip  repeated  the  with  to  force with  tested  the  the  had  the  cone  to  set of tests  n o s e - b o o m s of rpm,  of  [12]  1.27  involved  cm  length.  speed  the  model  spin  assess  of  pitch was  the  angle  pitched  reversed.  Two  made: spin  determines  A clockwise rotation  the  direction  leads to a net  of  the  left side force  side (as  LO  O LD  Lb / L  A  0.0 0.010  +  0.032  X  0.041  o  o  0.063  V  0.083  in  o _ I  0.0  20.0  10.0  30.0  40.0  50.0  60.0  o., d e g . Figure  3-17  Side force variation as affected b y pitch angle a n d n o s e - b o o m l e n g t h a t t i p s p i n r a t e o f 2000 r p m .  58 viewed  ii)  by  the  anticlockwise  spin.  Ericsson and  Reding  The  tip  rotation  force.  Figure  These  results  nominal value  The  maximum  2000 r p m ,  was  length  the  the  in  nominal  tip  was  quite  The  a range  spin  rate  of  are  determined  set  at  200  a  rpm  yielding  the  same tip.  the  maximum  range  of  with  the  results  by  in  the  the  nominal  actually to  involved force  that  the  reduced  a  a stable  spin rate  below  100  rpm.  In  fact,  any  25% o f t h e  spin  reduction  100-400  rpm.  seems to  nominal value  Investigations in  by the  a  other side  clear  the  force  occurs  75%  spinning  of  at  same  boom  side  force  from  standard  cm  nose-boom  pitch and of  motor  in  the  rotation it  the  has  was  with side  side force  46% o f t h e  researchers  to  variation  minimum  reduce  and  sense  force  various  the  1.27  present  Note,  50%  with the  the  side  71%.  the  nose-boom.  Again  side  of  spinning  by  spinning variation  maximum  of  the  With  cm  of  rpm.  Note,  direction.  the  in the  nose-boom tip  force  shows  the  with a nose-boom.  side  3-20  3-19.  tip  value).  note  of  Figure  range  increased  side force  side  2000  spinning the  interesting  tests  at  in  1.27  rpm.  for  effectiveness  side force  reduction  tests  The  true  significant reduction  with the  speed.  possible to obtain  rate for  (of  is  shown  the  Figures  agreement  r e d u c t i o n w i t h a 0.318  is  effective  second  over  that  25%  It  to a  r e d u c i n g the  nonspinning  value.  in  demonstrates  c a n be o b t a i n e d  around  is  opposite  [15].  3-18  show  side force  The  This  c a n lead  nose-booms in  the  pilot).  spin force  with  zero spin case,  [12,  15]  at  spin  suggests rates  not  in  200 for that the  Figure 3-18  Effect of the nose-boom length on the side force coefficient at 2000 rpm.  IT)  SPIN o v v a  RPiTE, RPM = 2000 = 2000 = 1200 - 1200 a - 700 x - 700 x - 525  O LO  CLOCKWISE  • • © ©  = =  a = a =  a = a =  LT)  B = I  0.0  20.0  10.0  30.0 a,  Figure  40.0  50.0  60.0  deg.  3-19 Side f o r c e v a r i a t i o n a s a f f e c t e d b y p i t c h a n g l e a n d s p i n r a t e f o r a 1.27 cm nose-boom.  525 410 410 300 300 200 200 100' 100  (] (0)  ( B r a c k e t t e d numbers a r e % r e d u c t i o n f r o m t h e 1 . 2 7 cm nose-boom's s t a t i o n a r y value)  0.0  1  1  1  500.0  1000.0 SPIN R A T E , RPM  1500.0  Figure  3-20  Effect  of s p i n rate  coefficient for a  on the  1.27  side  2000  force  cm n o s e - b o o m .  62 Results for the normal force coefficient as affected by length and  spin rate are presented in Figure 3-21.  Cn is virtually unaffected  by these parameters.  the  boom  It iB apparent that  o  Figure 3-21  The normal force coefficient as affected by: a) the nose-boom length at a spin rate of 2000 rpm.  Figure 3-21  The normal force coefficient as affected by: b) the spin rate for a 1.27 cm nose-boom.  65 CONCLUDING  4  The far  more  subject complex  happens  in  sometimes  invalidate not  p r o b l e m s of a n  the  first  the  only  impressions of  in  which  results.  the  flows  would  subject  involved aerodynamic  only  present  matter,  testing  proven  to  As  many  complicate,  study  but  be  often  phenomena,  not  The  has  indicate.  aerodynamic  appear  test  forebody  in  but  proved  to  be  procedures  and  scheme.  CpnclMSiplQS The  provides,  carefully for  effectiveness force with  the  of  first  several  better  following  i)  tip  tip  geometries with  of  and  a  be  Regardless it  is  of  the  cone-cylinder and  flow.  on  on  side  provided  apex,  information Based  the  the  model,  porous  study  a n g l e s of study at  that the  attack of  as  delta  leading the  true  of  can  effects  many  worst  hypotheses  undeniably  with  results  concerning  rotation  fundamental  repeated  possible to e n s u r e  their  authoritative high  repeatable  to  results  made:  comprehensive  must  28°  complex  c o n c l u s i o n s c a n be  without  onset,  given  the  c h a r a c t e r i s t i c s at  ii)  and  nose-booms without have  a  with  information  tip,  complete  Tests  reliable  tests  appreciation  A  time,  rotation,  general  experiments  The  standard and  planned  the  reduction.  strakes a  than  dominated  parameters  education,  4.1  vortex  investigations  uncontrollable  an  of  REMARKS  of  roll  side  not the  that  complete  roll  angle.  orientations  configuration concerning  be  force  as  is c o v e r e d ,  the  microasymmetry  side of  force either  the to  tip  surface  trigger  switching  roughness  to  asymmetric  flow  The  the  asymmetric  direction  iii)  or  effect  be  of  with  an  roll  entire  hypothesis  that  stream  vortex  major  suggests  parameter  the  attendant  flow  can  the  surface  sufficient  positions,  orientation  body or  is  The  roll  and  turbulence  development.  important  pattern  rolling the  triggering  free  tip  be  in  surface an  force,  assessed  by  either  This supports  the  responsible  for  asymmetries are  force  initiating  side  alone.  asymmetries  side  confined  to  the  tip  region. iv)  Plots  of  attack  pressure show  side.  by  attributed  nearly  The  other  is  surface on  one  survey the  significant  the  side  equal  to  the  Bame  order  of  angles  the  visualization area  close to the  side of the  occurs  magnitude  at  a  The as  is  cone  cone  separated  angle.  of  leeward  pressure  line  force cone  of  flow  low  leeward  high  half  and  of a v o r t e x  of the  at  pressure indicating a fully  the  of  low  literature  half  approximately  side force  cone  quite  presence  uniform of  the  researchers,  The other  onset  angle  be  the  to the  surface.  v)  to  Based on  studies  a  it  over  has  flow, pitch  maximum  the  normal  force. vi)  The  normal  orientation.  force  is  relatively  unaffected  by  the  roll  67 Nose-Boom i)  A B in the case of the standard tip, the roll orientation continues to affect the side force, even in the presence of a noBe-boom.  ii)  By properly  choosing the size of a nose-boom, the side  force can be reduced  by as much as 50%.  However, it  appears that too short a nose boom is worse than none at all as a 34% Increase in the side force was recorded with a 0.32 cm nose—boom (Lb/L  =  3.1%).  In fact, the nose—booms  shorter than 7% of the cone length increased the maximum side force while the opposite was true for the nose-booms with Lb/L > 0.07. iii)  Tests with the nose-booms of lengths less than 7% of the cone length exhibited a greater instability of the flow field. Large changes in the side force magnitude and direction with roll orientations were frequent with shorter  booms.  This  several  agrees  with  the  trend  observed  by  investigators in their studies with slender cones. iv) The normal force is relatively insensitive to both the noseboom length and roll orientation. E o r p u s .Tip_wifch.NQse-Boora  i)  A side force reduction of nearly 50% is possible with the addition of a porous tip having a 3.18 cm nose-boom.  i) A side force reduction by at least 88%, and possibly greater, is achievable with an appropriate delta strake.  The largest  strake used in the test program (21% of the cone length)  exhibited  the  irrespective the  cone  the  shortest  best  of  side  their  length),  force  lengths,  reduced  strake  alleviation.  except  the  behaved  the  All  strakes,  shortest  side  force.  almost  like  The the  (2.1%  model  of  with  standard  tip  configuration. ii)  An  orientation  plane  is  slightly  A  small  in  a  lower  iv)  roll  but  the  largest  stability.  far  with  the  tip  strakes  less  as  to  50%  larger  than  increase in the  a  the  the  pitch  results  from  strake,  as  a  of  the  pitch  plane. this  A more  encountered  slightly  higher  side  encountered  with  ±10°, indicate  that  that  delta  the  positive the is  cone  tip  reduced  length the  becomes in  size.  appeared same  to  trend  model, was o b s e r v e d with  The  normal force  length.  F o r all  reduction  directional  system  Incidentally,  normal force  c o m p a r e d to the  force.  but  strake  12% o f  strake.  negligible  B =  decreases and  standard  strake  at  weak  stability.  of a delta  this  strakes,  the  addition  side  delta  leads  than  delta  decrease in the  the  the  flight,  A slight  consequence  of  stability  directional  purposes,  to  coefficient  promotes  was o b s e r v e d for  an  parallel  to  tip.  unstable  promote  v)  force  orientation  The  strongly  that  perpendicular  configuration,  standard tests  The  side  still  Yaw  strake  to  noncoordinated  force the  the  preferable  conventional iii)  of  decreases  the with  practical  i n lift is of  associated large  little reductions  in  69 .Spinning .Tips  i)  Spin For  direction determines the direction of the side the test Reynolds  number of 1.1 X 10 , there 5  force. is no  Magnus lift reversal and the side force is always to the left for  clockwise  spin  and  to the right  for anticlockwise  rotation (as viewed by the pilot). ii)  Reductions in the side force of up to 75% were possible with spinning  tips.  Tests  with various sizes of the nose—booms  spinning  at 2000 rpm showed that a smaller boom length is  more effective in alleviating the side force. percent rpm iii)  reduction  A  seventy-five  in the side force was achieved  at 2000  with a 0.32 cm nose-boom,  Spinning of the nose-tip does not increase the side force.  iv)  A clear minimum observed (Lb/L  v)  A  at  side force coefficient (75% reduction)  200  rpm  for  the  1.27  cm  was  nose-boom  = 0.318).  complex  interdependence  of the spin  rate, tunnel  test  speed, angle of attack and nose-boom length is evident.  A  separate more elaborate and carefully planned test-program is necessary to fully appreciate these interactions.  4.2 Recommendations As  in any study  aimed at understanding a phenomenon at the  fundamental  level,  appreciation  of the process.  understand  more  the side force  new  questions This  arise  experimental  as  one  program  phenomenon i s no exception.  following recommendations involve extension  has  better  trying to  Most of the  of the present test-program.  70 Several  of  the  porous  tips)  side are  associated fluid basis  alone.  individual's  of  the  may  for  one  or  and  other  Industrial,  be  in  from To  manufacturers, evolve  coordinated  end and  rational  to  to  of  the  pressure  per  further  study.  following  the  special range  operational side  in  NASA,  engineers  have  wide  feasible  as  that  upon  and  promise  such  the  on  addition,  the  and  of  receive  narrow  little  maintenance  consultation  in  may  distinguish  have  terms  Depending  group  agencies  plan  in  manufacturing  which  this  pilots  a  order  those  strakes),  prefer  (spinning  investigation  applications.  the  here  interest  delta  h a n d , one may  polled  studied  merit further  topics.  application.  to  hence  practical  other  devices  consulted  and  devices  fundamental  (nose-booms  scope  research  practical  such  mechanics  On the  alleviation  alleviation  considerable  interest,  requirements  missile  of  Others  considerable  attention.  force  force  terms  aircraft  should Even  of and  also  in  be  absence  recommendations  seem  appropriate: i)  Twelve  describe  the  pressure  taps  taps  pressure at  ring  is a minimum  distribution.  certain  stations  The  to  adequately  addition  s h o u l d be  of  more  seriously  considered. ii)  The  model s u p p o r t , although  previous  state  vibrations the iii)  The  limited  maximum use  of  angle a  recommended procedure.  [13],  could stand  the  The  tests  a  and  further  to the  of attack  reliable as  much improved  of  wind  Department  on of  its  modification. speed  (22.7  Model  m/s)  and  50°.  calibrated  check  from  the  force  balance  pressure  Mechanical  table  is  integration  Engineering  has  71 just  iv)  acquired  such  operational  at  The  more  u s e of  better The  the  of  system  complete the  LDV,  hot  v)  flow  wires  and  aircraft  F-18  of  aircraft  purpose It  as they  prove  this  forebody do not  of  It  be made  the  to  model.  although  understanding  presently further  study  side  alleviation  force  of  tested  application  to of  arrive this  alleviation  of  device  the  device  also recommended for study  at  to  porosity,  require  further  examination.  to  and  purchased but  size  new  model to match  incorporate  effectiveness.  tip  of  the  the may  use  to  best been  and  shapes  could  aircraft  The nose  is  results, as  with  filter be of  existing  tip  be the  a  side  Parameters  fuel  proved  into tip  A  to  strake  has not  an  concept  its  this  geometry.  of the  recommended.  length,  and  model  porous  porous  was  a  F-16  yet  optimum  substantiation  the is  aspect ratios  for  delta  found as  that an  a nose-boom.  of the  and  an  useful  acquired  T h i s was  Different lengths,  and  incorporate  geometry  for  n o s e - b o o m to  or  out.  bronze  the  visualization,  is recommended  be c a r r i e d  Further  around  interesting  effectiveness  optimized.  vii)  flow  improve  an  work.  is recommended that  be  is recommended  structure  various lengths  model would  substantiation  vi)  greatly  not  program.  instrumentation field  was  phenomenon,  The application of  or  unfortunately,  present  flow  time c o n s u m i n g w o u l d this  which,  time of t h e  understand  use  a  such  other made  the  of  wrong  model.  force as  devices porous shape  Perhaps  be c o n s t r u c t e d to a s s e s s  a its  72 viii)  The  porous  connected  tip to  the  communicated of  the  body  As  the  the  force  cavity  of  these  results  of  the  from  reduction  optimization  spin rate  the  but  merits  and  present  wake  be  through  it  also to t h e  of the  tip  the by  model, is  an  study. has  The  not  been  recommended  that  r e s p e c t to the  wind  is  be n o n d i m e n s i o n a l i z e d with  on  rotation  further  It  is  examined  nose-boom length  study.  It  pressure  rest  and was  model.  base  the  hollow  Pressure  the  characteristics  phenomenon,  in  of  was  model.  center  effect  interesting  achieved  program  cone  the  porous tip  side  test  circumferentially  alleviation  isolating the ix)  the  hollow  through that  force  in  not o n l y  recommended side  used  speed. x)  Finally,  a  statement  analytical/numerical literature showed have the  review,  little  be  investigation. computer  promise.  models  codes,  with  the  made  Earlier,  modeling  However,  developed computer numerical  should  of  the  recently  and  on during  the  complex  flow  several  compared the  experimental  an  data,  authors  results which  of are  encouraging. xi)  It  is  suggested  a n d A d a m s [25], particularly tip  rotation.  process  with If  that and  the  approaches  F i d d e s [30]  respect  to  successful,  significantly.  the this  presented  s h o u l d be various would  by  explored  tip  Newsome further,  geometries  facilitate  the  and  design  73  BIBLIOGRAPHY  [1]  2-D  and  14-16, [2]  Allen,  3-D  1980,  Strength Large pp. [4]  Pasadena, Calif.,  K.D., of  Asymmetric  Loads  in  No.  the  Wake  of  Flow  Over  Inclined  1951. 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[24] Almosnino, D., "High Angle of Attack Calculations of the Subsonic Vortex  Flow  on  Slender  Bodies", AIAA .21st  Aerospace  Sciences  Meeting, Jan. 10-13, 1983, Reno, Nev., Paper No. AIAA-83-0035. [25] Newsome, R.W.,  and Adams, M.S.,  "Vortical Flow  over an Elliptical-  Body Missile at High Angles of Attack", Journal of Spacecraft and Rockets, Vol. 25, No. 1, Jan.-Feb. 1988, pp. 24-30. [26] Chan, Y.Y., "Side Force Computations  for Slender Bodies by a Far  Field Approach", Journal o f .Spacecraft and Rockets, Vol. 25, No. 1, Jan.-Feb. 1988, pp. 9-18. [27] Seginer, A., and Attack  and  Mechanics  Ringel, M.,  Critical  Reynolds  .Conference,  August  "Magnus  Effects  at High  Angles of  Numbers"., AIAA.... Atmospheric.. ..Flight 15-17,  1983, Gatlinborg,  Tennessee,  Paper No. AIAA-83-2145. [28] Ericsson, L.E., "Flat  Spin of Bodies with Circular Cross-Section",  AIAA_AtmQSBh.eric..__EM^  August  15-17, 1983,  Gatlinborg, Tennessee, Paper No. AIAA-83-2147. 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Hussaini and M.D. Salas, Springer-Verlag, New York, 1987, 311-364.  pp.  78  APPENDIX  As  pointed  pressure divided where  taps into  the  vary  number  from the  tap  direction,  hence a  Each segment.  segment the  of  of e r r o r tap  unequal  perimeter  (C)  each to  of  of  cone this  that  are  the  p o l y g o n at each side  Si = 2Ri*Sin(n/n),  where  the  Ri = Li*Tan(5)  and  • Hi,  L»»n)  = (Li  2  -  where the  Thus:  L(„n) ) 2  Tan(6)  was  the  tap, force  pressure  pressure  does  circumferential procedure  does  trapezoidal  by  a  regular  shaped polygon  area of  (Si) (Ri)  location  is g i v e n  i  is  by,  is  at  station  i.  is  Cos(6) Ai  a  cone length  2 Hi = L i -  the  the  Sin(n/n) Cos(6)  40  10%.  a reference  radius  Li is the  of each trapezoid  A i = S i + S(bn)  to  1-1).  hence  (Ai)  by  is  The  integration  described  Ci = 2nRi«Sin(n/n),  The area  in  24  pressure  Thus,  segment.  coarse  (Figure  a  surface  especially  with  cone surface  constant.  cone  surrounded  edges  The  surrounding  be  the  DATA  provided  used.  of a p p r o x i m a t e l y  is  of  model was  nose tip  area  the  use  sides i n s c r i b e d in a circle The  the  assumed  times  pressure  cone  segments,  around  degree  The  of  was  the  the  upon  each  considerably  introduce  earlier,  pressure  at  INTEGRATION OF PRESSURE  depending a  contribution measured  out  I:  height  of  the  trapezoid  Hi i s :  n  79 The  resultant  resolved into  pressure  normal  and  side force  = NORMAL FORCE *  FH  forces  2 Pi  exerted  upon  components as  • Ai  • S i n 6i  •  the  cone  can  CN  = 2 Cpi  forces in terms • Ai  • S i n 81 •  of  be  follows:  Cos(6);  Fs = SIDE F O R C E = 2 P i • A i • C o s 6i • Cos(8); w h e r e circumferential a n g u l a r position of e a c h p r e s s u r e tap.  Expressing  now  0i i s  the  coefficients:  Cos(6)  — ^ — — ^ — — — — — — — — ^ —  ;  AB Cs  = 2 Cpi  • Ai  • C o s 8t • C o s ( 6 ) AB  w h e r e AB As force of  drag  instead  is the and of  cone base area *  axial  lift  force  forces is  were  more  D /4. 2  not  logical  measured, and  the  use  conventional  of  in  normal  this  type  investigation. The  FORTRAN  program  used  to  integrate  the  pressure  data  attached.  Figure  1-1  Division of the  cone surface into area  segments.  is  C C  P R O G R A M TO R E S O L V E F O R C E S ON A C O N E I N T O L I F T D R A G AND S I D E F O R C E REAL A ( 4 0 ) , C P ( 4 1 ) , L ( 4 0 ) , T ( 4 0 ) . L I F T , T T ( 1 2 ) , C P P ( 1 2 ) INTEGER ALPHA1.ALPHA2,NOSE,ROLL CHARACTER TESV30 A I S THE ARE SURROUNDING EACH PRESSURE TAP CP I S T H E C O E F F I C I E N T OF P R E S S U R E FOR E A C H T A P L I S T H E L E N G T H OF E A C H AREA S E G M E N T M E A S U R E D FROM THE T I P T I S T H E O R I E N T A T I O N I N R O L L OF E A C H T A P CA I S T H E C O N E H A L F A N G L E A L P H A 1 I S T H E F I R S T A N G L E OF A T T A C K F O R E A C H T E S T ALPHA2 I S THE LAST A N G L E OF A T T A C K FOR E A C H T E S T NOSE I S THE NOSE ROLL P O S I T I O N R O L L I S T H E BODY R O L L P O S I T I O N T E S T I S T H E T I T L E OF E A C H E X P E R I M E N T  C C C C C C C C C C C C C C F I R S T FOR T H E A R E A S PI=3.1415926 CA=ATAN(.25) L(1)=6.0 L(7)=5.0 L(13)=4.125 L(19)=3.25 L(25)=2.25 L(37)=1.25 DO 1 N = 1 , 5 L ( 1 + N ) = L ( 1) L(7+N)=L(7) L(13+N)=L(13) L ( 19 + N ) = L ( 1 9 ) 1 6  L(41-N)=L(37) DO 6 N = 1 . 1 1 L(25+N)=L(25) DO 2 N = 1 , 2 4  A ( N )= ( L ( N ) * * 2 - L ( N + 6) "2)'TAN(CA)/COS(CA)/2. DO 3 N = 2 5 , 3 6 3 A(N)=(L(N)'*2-L(37)*'2)*TAN(CA)'SIN(PI/12.)/COS(CA) DO 12 N = 3 7 , 4 0 12 A ( N ) = L ( N ) • * 2 * T A N ( C A ) / C 0 S ( C A ) * S I N ( P I / 4 . ) 2  C C C C C C C  DO  FOR  DO  J=1.24  7  VARIOUS  TESTS  DO L O O P F O R V A R I O U S A N G L E S I N P U T R O L L A N G L E , A N G L E OF  70  25 C C C  LOOP  OF A T T A C K A T T A C K , NOSE  READ(5,70) TEST FORMAT(A30) WRITE(7.70)TEST READ*.ROLL,ALPHA 1,ALPHA2 WRITEC 7 , 2 5 ) R O L L , A L P H A 1.ALPHA2 FORMAT(3(I5))  CALCULATE  TAP  ROLL  POSITION  T(1)=(3.0+R0LL)*PI/6.0 T(2)=(5.0+R0LL)'PI/6.0 T(3)=(7.0+ROLL)'PI/6.0 T(4)=(9.0+R0LL)'PI/6.0 T ( 5 ) = ( 11 . O + R O L D ' P I / 6 . 0 T ( 6 ) = ( 1 . 0 + R O L L ) * P I / 6 .0 DO 4 N = 1 . 3 T(6*N+1)=T(1) T(6*N+2)=T(2) T(6*N*3)=T(3) T(6*N+4)=T(4) T(6'N+5)=T(5) 4 T(6*N+6)=T(6)  POSITION  T(25)=T(1)-.3578 DO 9 N=1 ,11 9 T(25+N)=T(24+N)+PI/6. T(37)=T(25) DO 11 N=1,3 11 T(37+N)=T(36+N)+PI/2. DO 21 N=1,40 PI2=2."PI 21 IF(T(N).GE.PI2) T(N)=T(N)-PI2  C C INPUT PRESSURE MEASUREMENTS C DO 7 K=ALPHA1,ALPHA2, 10 READ(5,20)CP 20 FORMAT(12(F10 . 4) ) Q=CP(41) DO 5 N=1,41 5 CP(N)=CP(N)/0 C SORTING OF ANGLES AND PRESSURES LF = 25 DO 22 N=26,36 22 IF(T(LF).GT.T(N)) LF=N DO 23 N=1,12 LFF=LF+N-1 IF(LFF.GT.36) THEN KK=LF+N-13 ELSE KK=LF+N-1 ENDIF TT(N)=T(KK) 23 CPP(N)=CP(KK) WRITE(7,35 )TT 35 FORMAT(12(F10.4) ) WRITE(7,35)CPP C C INTEGRATE FORCES C LIFT=0.0 SIDE=0.0 DO 6 N=1,40 LIFT=LIFT+A(N)"CP(N)*COS(CA)*COS(T(N)) 6 SIDE=SIDE + A(N)'CP(N)'COS(CA)'SIN(T(N) ) CL=LIFT/(2.25'PI) CS=SIDE/(2.25'PI> C C NOW FOR SOME RESULTS C C WRITE(6.60) TEST 60 FORMAT(2X,A30) C WRITE(6,40) ROLL.K.CL.CS 40 FORMAT(5X,'FOR ROLL POSITION ',13,' AND FOR ANGLE 2'0F ATTACK ',13, 3' CL AND CS ARE ',2(F10.4) ) WRITE(7,45)CL , CS 45 F0RMAT(2(F10.4) ) C WRITE(6,50) C 50 FORMAT(' PRESSURE COEFFICIENTS FOR EACH TAP') C WRITE(6.30) CP C 30 FORMAT(6(F10.4)) 7 CONTINUE STOP END  

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