Parameter Studies on Rotational and Translational Accelerations of Flat Plates

We compare a broad range of transient translations, and a smaller collection of transient rotations, of flat plates of aspect ratio 2, 4, and nominally 2D, tracking lift and drag coefficients vs. motion history, for a range of acceleration profiles and motion modalities, and for Reynolds numbers from 14 through 10,000. Kinematics include a translational acceleration, consisting of a linear ramp in velocity vs. convective time, starting from rest and with fixed incidence angle; a pitch about various chordwise pivot points in constant free-stream; a combination of the two, with both pitch and translational acceleration; a plunging motion in steady free stream; and finally, a rotational acceleration, where the plate is again initially at rest and accelerates azimuthally to some steady rotational speed. Accelerations cover reduced frequencies from K = π/48 to π/4. Rotational and translational accelerations where studied in mixtures of glycerin and water, as well as nominally pure water, as a means of broadly varying Reynolds number. Noncirculatory loads vary as the square of the reduced frequency, and are particularly pronounced during smoothing-transients applied to linear ramps. For the cases of pitching and combined pitching and translational acceleration, moving the pitch pivot point aft delays leading edge vortex production and attenuates lift. At Re = 10,000, which was the principal Reynolds number achieved in pure water, lift and drag histories are essentially identical for the translational acceleration case. The same is true for the rotational acceleration case, implying that the net aerodynamic force is wall-normal. Further, the shape of the aerodynamic force histories is similar between translation an