This paper reports the bistability of curved compression ramp (CCR) flows, revealing that both separation and attachment states can be stably established in CCR flows. A thought experiment is firstly proposed, in which it is possible to construct two different stable CCR flows with the same boundary condition through two different processes. Both processes consist of the same three steps but in different orders, so as to investigate the effects of initial condition and evolutionary history on CCR flows. To answer whether CCR flows' bistability is possible, direct numerical simulations are performed to replicate the thought experiment, confirming its existence conjecture. To answer how CCR flows' bistability is possible, a virtual separation disturbance is imposed into the flows to investigate three characteristic adverse pressure gradients, clarifying the necessary and sufficient conditions for the emergence of bistable states. As a classic type of shock wave boundary layer interaction (SBLI) and usual local geometric configurations of aircraft, CCR flows' bistability implies global flows of real supersonic/hypersonic flight dominated by SBLI could also have multistable states.

Based on the Helmholtz–Rayleigh minimal dissipation theorem, a theoretical model is proposed to predict both the plateau and peak of pressure in a compression ramp flow with large separation (CRFLS). Since the total dissipation of CRFLS is mainly contributed by the shock waves, the steady flow pattern can be determined by minimizing the shock dissipation among all the possible configurations. The predictions agree well with both experimental data and numerical simulations, covering a wide range of free-stream Mach number and ramp angle. This method could be applied to other flow systems where the dissipation is dominated by shock waves.

No abstract

No abstract

No abstract