UBC Theses and Dissertations
On the experimental investigation of vortex excited pressure fluctuations Heine, Walter
Construction and calibration of a piezoelectric transducer capable of measuring acoustic level pressure fluctuations occurring on the surface of a body due to shed vortices is described. The application of the transducer as a wake survey equipment is also explained. The fluctuating pressure and wake geometry study carried out using two dimensional models of several bluff and streamlined bodies indicate that (1) Fluctuating lift coefficient decreases with reduction in bluffness of the body. (2) For square and rectangular cylinders, as well as for the elliptic cylinder at large angles of attack, the amplitude of fluctuating pressure is minimum at the points where static pressure is maximum. (3) Fluctuating lift coefficient for the bodies with sharp leading edge (e.g. square and rectangular cylinders) is considerably larger than the corresponding static value, while for the circular cylinder, elliptic cylinder and the wing, the fluctuating coefficients were found to be smaller than their static counterpart. (4) The self excited motion of the body, particularly a bluff body, does not affect either the frequency of shedding vortices or the fluctuating pressure, for frequencies above vortex resonance.
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