Research on starting characteristics of two-dimensional supersonic inlet by using unsteady numerical simulation

To investigate the starting characteristics of a two-dimensional supersonic inlet influenced by various factors, such as contraction ratio (CR) and inflow Mach number, an unsteady numerical simulation using a dynamic mesh technique is utilized. The study focuses on an inflow Mach number range of 2–4 and a CR varying from 2 to 5. The results indicate the presence of two types of unstart events: one caused by flow separation and the other by throat flow congestion. For inlets without bleed systems, as the Ma0 decreases, the inlet experiences unstart due to flow separation. However, as the CR increases, the inlet will undergo unstart resulting from flow congestion. Similarly, for inlets equipped with bleed systems, as the Ma0 decreases, the inlet will also experience unstart caused by flow congestion. When both inflow Mach number and CR undergo simultaneous changes, the inlet's starting status can vary, depending on which factor has a more significant effect on the flow field, as indicated by wall pressure fluctuations. Furthermore, an empirical equation of starting prediction is deformed to take into account the effects of inflow acceleration and rotation angular velocity of compression ramp, thereby broadening its application range from steady state to unsteady state.