Research on a Rapid Method for Obtaining the Matching Point of the Static Operating Pressure of a Supersonic Jet in a Wind Tunnel

Abstract

In the wind tunnel test, mismatched operating pressures can cause the jet flow field to produce expansion waves, compression waves, and wave interference. The current wind tunnel pressure matching study requires continuous adjustment of the operating pressure at the inlet and outlet to obtain an ideal supersonic jet in an expanded state, and the pressure matching workload is substantial. This study presents a numerical simulation of the flow field of a supersonic wind tunnel under different outlet pressures based on the Reynolds-averaged Navier-Stokes (RANS) method. A method for quickly obtaining the static operating pressure matching point of a supersonic jet is proposed, which can quickly determine the matching operating pressure. When the Mach number of the monitoring point on the axis of the core area of the jet is within 5 % of the standard Mach number at the nozzle outlet, the jet in the wind tunnel test chamber is in an ideal expansion state, and the outlet pressure under this condition is the standard operating pressure for pressure matching. At the same time, the flow field structures under the conditions of over-expansion, ideal expansion, and under-expansion were compared, and it was shown that the key physical parameters in the core region of the supersonic jet field under the ideal expansion state obtained by this rapid matching method were stably distributed, which allowed the uniform region of the jet to exceed the limits of the diamond region and achieve uniform flow within the boundary of the supersonic jet.