Study on Backward-Facing Step Flow and Performance of Cryogenic Wind Tunnel Driven by Flashing Liquid Nitrogen

Abstract

The experimental study has been conducted to estimate the performance of a cryogenic wind tunnel by using flashing liquid nitrogen and the location of reattachment at the downstream of the backward-facing step. Total and static pressure and temperature of the flow in the test section are measured to calculate flow the Mach number and Reynolds number. Flow visualization by color-schlieren method was also performed. Liquefied nitrogen at a pressure of 700 kPa produced the uniform flow, of which the Mach number and total pressure ranges were 0.08 to 0.8, and 20 to 200 kPa, respectively. The Reynolds number based on the step height (5 mm) ranged from 0.15 × 10 5 to 0.44 × 10 5 , and the duration of stable operation was limited to 0.4-0.8 seconds in our configuration. The results indicated that the prediction by FFT analysis to the reattachment location over the backward-facing step was good agreement with that of their static pressure distributions and visualization results.