Experimental Study of Dynamic Characteristics of Oblique Shock Trains in Mach 5 Flow

Abstract

The oblique shock train (OST) flow diffusion phenomenon, which involves an interaction between the duct’s peripheral boundary layer and central oblique-shock-wave field, usually appears in constant or nearly constant cross-sectional-area supersonic/hypersonic duct flows. The study of such a complex flow structure in a confined duct under a finite adverse pressure gradient has important implications for the design and operation of a variety of devices including hypersonic vehicle inlet/isolator [1, 2], supersonic wind tunnel diffusers [3], supersonic ejectors, and so on. To develop the design methods and control strategies of the flow devices, it is necessary to fully understand the mechanism of the OST. Different flow conditions will lead to different kinds of shock train structure: normal shock train occurs for lower incoming Mach numbers of about 1.2–2, whereas oblique shock train occurs for higher incoming Mach numbers. The aerodynamic performance of the fluid devices is well related to the features of the OST, which include the structure of the OST, the pressure recovery in the OST flow region, the dynamic characteristics of the flow separation region nearby the OST, and so on. In addition to complex flow structure, the OST inside the duct has an important feature of unsteady characteristics; even if the boundary conditions such as the pressures upstream and downstream of the OST region are held constant, the OST is still in “self-oscillation” state [4]. This self-excited oscillation may cause the structural fatigue, unstart of inlet/isolator, and instability of combustion. Therefore, the study of dynamic characteristics of the OST is important for aircraft structural design and aerodynamic performance evaluation.