The interaction between a normal shock wave and a boundary layer in supersonic internal flow causes a very complicated flow. The complicated flow is called as pseudo-shock wave. Pseudo-shock wave commonly occurs in confined, internal, supersonic flows where normal shocks are supposed to stand and interact with wall boundary layers. Nowadays, the research field of pseudo-shock wave in supersonic internal flow is mainly based on the isolator of scramjet engine, so the focus of the present work lies on the essential features of the pseudo-shock wave in the scramjet isolator.
The pseudo-shock wave draws the attention of the researchers mainly in two aspects of flow characteristics. First one is the static characteristics and other is the dynamic characteristics. In this study, static and dynamic characteristics of pseudo-shock wave have been investigated. The numerical results of the pseudo-shock wave have been demonstrated, which is helpful for the better understanding of this flow phenomenon. The Computational Fluid Dynamics (CFD) method based on Fluent is applied to simulate the flow field of pseudo-shock wave in supersonic internal flow.
Many application fields of pseudo-shock wave are based on the rectangular duct, so the focus of the present work lies on this object. The purpose of the present study has been to explore the static characteristics of pseudo-shock wave in rectangular duct by numerical method. Reynolds stress turbulent model (RSM) coupled with an implicit formulation are used considering the accuracy and stability of individual case. A finite volume scheme and density-based solver with coupled scheme is applied in the computational process. The overall static characteristics of the pseudo-shock wave can be determined based mainly on four parameters, such as, inlet Mach number, inlet boundary layer thickness, inlet total temperature and inlet boundary layer velocity profile. Flow structures and some related parameter variations of the pseudo-shock wave have been revealed and analyzed. Pressure distribution and separation flow condition along the wall have been analyzed.
Dynamic characteristics of pseudo-shock wave also draw more attention of the researchers. The dynamic characteristics are the important factors in the design of supersonic internal ducts. The objective of the section is to explore the dynamic characteristics of the flow oscillations caused by the shock wave/boundary layer interaction. The dynamic characteristics of pseudo-shock wave in supersonic internal flow have been investigated by using large-eddy simulation (LES). Root mean square (RMS) value of pressure fluctuation has been used to study the self-excited oscillation of pseudo-shock wave. The results show that the biggest peak of pressure fluctuation occurs at shock train region. It is caused by both of streamwise shock motion and spanwise shock fluctuation.
The boundary layer development along the wall is subjected to severe adverse pressure gradients which can cause boundary layer separation and unsteady flow. The control technology of pseudo-shock wave with grooved wall has been tested in terms of the flow separation and total pressure loss. The objective of this section is to investigate the effect of grooved walls on pseudo-shock wave. A computational fluid dynamics (CFD)-based study has been conducted with Reynolds stress turbulent model (RSM). The structure of pseudo-shock wave in the duct has been controlled by grooved walls. The counter-rotating vortices are produced by grooved control. The shocks become weaker in the core flow with grooved walls. It produces a beneficial reduction in total pressure loss. Effect of grooved wall to weaken the boundary layer separation has also been evaluated by numerical simulation.
Finally, the effect of pseudo-shock wave on the dual-mode scramjet has been evaluated. Dual-mode scramjet is one of the most important research fields of the pseudo-shock wave. The isolator is the critical component in dual-mode scramjet. In the present work, the isolator length has been optimized in terms of the characteristics of the pseudo-shock wave. Two-dimensional numerical model has been solved by the compressible Navier-Stokes equations. A fully implicit finite volume scheme has been applied to the governing equations, with a two-equation standard k-ω turbulence model. Throttling device has been applied to simulate the thermal choking condition. The effect of isolator length on the pseudo-shock wave has been investigated. The optimization of the isolator length has been done in terms of maximum back pressure and total pressure loss in the critical condition just before unstart phenomenon.