Sensitivity of The Boundary Layer Flow to Wave Perturbations Distributed on the Surface

In the paper , reaction of the boundary layer to forced oscillations in the form of a traveling wave distributed over the surface is numerically studied for various values of amplitude, length and phase speed of the initiated traveling wave . From t he practical point of view, there is an idea to preserv e a quasi -regular boundary layer structure as far as possible downstream with the accompanying effect of laminar to turbulent transition delay and drag reduction. The traveling wave initiated on the surface may be treated either as an active flow control through direct imposing forced oscillations distributed on the surface , or as a passive one when a compliant coating generates directed surface waves as a response to flow perturbations. The computation al results obtained show a high sensi tivity of the boundary layer vortex structure to unsteady perturba tions initiated on the surface in the form of a traveling wave . Convective instability of transverse vortices formed in the traveling wave troughs generates a vortex structure downstream strongly dependent on the trave ling wave length, phase speed, and amplitude . By imposing local surface oscillations close to the wave parameters of the boundary layer natural perturbations one can either delay laminar to turbulent transition process or, in fully developed turbulent regime, contribute to filling the turbulence pulsation spectrum with low frequency components.