Computation of flows in supersonic wind-tunnels

Abstract

Results are presented for finite-element computation of flows in supersonic wind-tunnels. It is demonstrated that the stabilized finite-element methods can be utilized to design and analyze supersonic wind-tunnels in general and the diffuser section in particular. The computations are capable of simulating the start-up problems associated with the wind-tunnels that are equipped with narrow diffusers and do not allow the start-up shock to pass through. The effect of various component geometries is investigated. It is shown, via examples, that the method may be used to find close to optimal values of the geometric parameters of the supersonic diffuser. A nozzle block that is designed purely by the method of characteristics, without boundary-layer corrections, fails to deliver a uniform flow in the test-section. In certain cases, even though a certain stagnation to exit pressure ratio may be able to start the tunnel, a higher pressure ratio may be desirable for better flow quality. Results for two benchmark problems, one involving flow in a double throat nozzle and the other a Mach 3 flow over a compression corner, have also been presented to establish confidence in the computations.