UBC Theses and Dissertations
Prediction method for spoiler performance Tam Doo, Peter A.
The prediction of the aerodynamic characteristics of a finite rectangular wing with part span spoilers is attempted using the lifting line theory of Prandtl. Required inputs to the theory are sectional values of lift coefficient, pitching moment coefficient, zero lift angle of attack, and aerodynamic center at selected points along the span. The value of these parameters for the spoilered wing sections is calculated by Brown's linearised thin airfoil theory for spoilers. This theory, in common with other sectional spoiler theories, requires as input the base pressure coefficient in the spoiler wake. The base pressure coefficient must be determined by experiment, since at the present time it cannot be predicted theoretically. The effect of base venting on spoilered section characteristics is examined experimentally. It is found that for small base vents of around ten percent of spoiler height or less, the vented section characteristics are little different from the unvented. Thus for the purposes of preliminary design, the unvented section characteristics may be used with little loss of accuracy, if the spoiler vent is about ten percent of spoiler height or less. The results of the finite wing theory are compared with experiment. Good agreement is found. The method is subject to the limitations of the lifting line theory, which limits its applicability to unswept wings of moderate to high aspect ratios operating at low subsonic speeds. The method is also subject to the additional limitations imposed by the sectional theories employed.
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