To aid in understanding the flow mechanism in supersonic inlet under the over-speed state

a numerical simulation was performed to obtain the flow structure of a rectangular inlet whose design Mach number was 2.0

operating under different inflow Mach numbers and backpressures. Results indicate: for the design case of Mach number 2.0

the core flow of shock train was deflected from the cowl-side surface to the ramp-side surface associated with the backpressure increase. While the inlet operated under the over-speed state

the core flow of shock train was deflected to the ramp-side surface firstly and then to the cowl-side surface due to the effects of the cowl-lip separation bubbles and the cowl shock in turn. For the case of inflow Mach number 2.5

a Mach-stem appeared at the joint point between forebody oblique shock and cowl shock once the backpressure increaseed to a certain value. However

this flow structure didnt appear in the case of inflow Mach number 3.0. Under the above two over-speed states

with the increase of backpressures

the transmit shock of forebody oblique shock was transformed into normal shock

and the transmit shock of cowl shock also changed its shape.