Response of a Hypersonic Boundary Layer to Wall Blowing-Suction

Abstract

In the laminar-turbulent transition of boundary-layer flows, the spatial development of boundary-layer waves, especially that of unstable waves, is important and indispensable. In this paper, the response of a Mach 8 flow over a 5.3 half-angle sharp wedge to wall blowing-suction is studied by numerical simulations. Steady base flow is obtained by solving the compressible Navier-Stokes equations with a combination of a fifth-order shock-fitting method and a second-order total-variation-diminishing scheme. In stability simulations, wall blowing-suction is introduced through an actuator on the wedge surface. The unsteady flow simulation is carried out using the shock-fitting method. The results show that mode F, mode S, acoustic waves, and entropy/vorticity waves are simultaneously excited by wall blowing-suction and coexist in the boundary layer just downstream of the actuator. For blowing-suction at a specific frequency, the results also show that mode S is strongly excited when the actuator is located upstream of the corresponding synchronization point. There is no significant amplification of pressure perturbation when the actuator is downstream of the synchronization point. This result represents a mixture of the receptivity and the downstream growth of mode S. The exact cause and mechanism of this result are not clear. However, such a result is obtained for wall blowing-suction at all frequencies considered in the current study. To excite a strong mode S at a specific frequency, the result indicates that it is necessary to place the blowing-suction actuator upstream of the corresponding synchronization point. Further theoretical analysis is needed to reveal the mechanism behind the numerical results.

Direct Numerical Simulation on the Receptivity, Instability, and Transition of Hypersonic Boundary Layers

“…Recently, the biorthogonal multimode decomposition was used to analyze perturbations in compressible and incompressible boundary layers (Tumin 2003). Tumin et al (2007Tumin et al ( , 2011 applied the multimode decomposition to analyze DNS results of hypersonic boundary layers over a flat plate ) and a sharp wedge (Wang et al 2011c). Figure 16 compares the theoretically predicted receptivity coefficient with that filtered out from the computational results for the case of a Mach-8 flow over a sharp wedge.…”

“…For small-amplitude blowing/suction, the growth rate of Mack's second mode computed by DNS agreed well with those predicted by the LST including nonparallel flow effects. Wang et al (2011c) studied the response of a Mach-8 flow over a sharp wedge to wall blowing and suction in which disturbances are introduced through an actuator on the wedge surface. Figure 7 shows the pressure perturbations along the wedge surface at the same frequency for the seven cases of simulations.…”

Stability characteristic of hypersonic flow over a blunt wedge under freestream pulse wave

“…They found that the wake vorticity field deformation at the flow around the leading edge plays a decisive role in streamwise vortex formation above the boundary layer and boundary layer distortion. Wang et al [16] investigated the response of a hypersonic boundary layer to wall blowing-suction. Stetson et al [17] investigated the hypersonic boundary layer stability of a blunt cone with 7…”

The stabilization of a hypersonic boundary layer using local sections of porous coating

“…A straightforward way to avoid first-mode destabilization is to put porous coating only where Mack's second mode is dominant. In a previous numerical study, Wang et al 25 showed that the synchronization point of mode F and mode S plays an important role in the excitation of mode S. The results indicate that the synchronization point might be the right location to start putting porous coating.…”