Role of the Synchronization Point on Boundary Layer Stabilization Using Porous Coating

Abstract

The role of the synchronization point on stabilization of a Mach 5.92 flat-plate boundary layer using a porous coating is investigated in current paper by a combination of theoretical analysis and numerical simulations. The study is motivated by Fedorov et al.’s experimental and theoretical studies of the effect of an ultrasonically absorptive coating on hypersonic boundary-layer stability [1] and our previous numerical simulations on hypersonic boundary-layer receptivity [2] . The steady base flow is firstly simulated by solving compressible Navier-Stokes equations with a combination of a fifth-order shock-fitting method and a second-order total variation diminishing (TVD) scheme. The stability characteristics of the hypersonic boundary layer is analyzed by linear stability theory (LST). In receptivity simulations, periodic wall blowing-suction disturbance is introduced near the leading edge to excite boundary-layer waves. Then porous coating is used near the synchronization point to stabilize boundary-layer waves. The numerical results show that at the frequency of 100 kHz, porous coating destabilizes boundary-layer waves when it is located upstream of the synchronization point and stabilizes boundary-layer waves when it is located downstream of the synchronization point. These results indicate that the synchronization point plays an important role on the stabilization of the hypersonic boundary layer using porous coating. The most efficient way to stabilize boundary layer is to put porous coating downstream of the synchronization point. At the frequency of 150 kHz, the behavior of pressure perturbation is hard to interpret. The complex behavior of pressure perturbation may be caused by the coexistence of mode S, mode F, and continuous modes in the boundary layer, because the synchronization point is quite near to the blowing-suction actuator.