Control of Vortex Breakdown by Small-Amplitude Perturbations of a Delta Wing

Control of vortex breakdown by small-amplitude perturbations of a delta wing. The consequence of unsteady actuators along the leading-edges of a delta wing can be simulated by small-amplitude perturbations of the edges of the wing, or the wing in its entirety. Perturbations control the onset and structure of vortex breakdown. For the case of the stationary wing, represented by the top row of images, well-defined regions of azimuthal vorticity arise immediately after the onset of vortex breakdown, vb. If the wing is perturbed at a period Te = 2 sec, relative to the period of natural vortex breakdown To = 1.6 sec, then the peak levels of vorticity in the breakdown region are substantially attenuated, and the distance between vorticity layers is decreased. On the other hand, perturbation at Te = 0.5 sec, as shown in the bottom row of images, results in substantial advancement of the onset of vortex breakdown to a location well to the left of the image boundary. As a result, the patterns of instantaneous vorticity exhibit a smaller streamwise wavelength relative to the case of the stationary wing. The perturbed forms of vortex breakdown shown in the middle and bottom rows of images are associated with changes in both the amplitude and frequency of the buffet velocity fluctuations along the upper and lower surfaces of the plate, as described in the corresponding manuscript. Mean and perturbation angle-of-attack of the delta wing are αp = 24° and αo = 1° respectively. Reynolds number is Re = 1.07x104.