Airfoil Flow Visualization and Pressure Measurements in High-Reynolds-Number Transonic Flow

Abstract

Today most wind tunnels operated for aerodynamic testing are not able to reproduce flight Reynolds numbers. To overcome this problem, a shock tube flow is used to generate a high-Reynolds-number transonic flow. With this technique, Reynolds numbers up to 40 × 10 6 based on model chord length are attainable in the Mach number range between 0.6 and 0.9. Time-resolved surface pressure measurements, as well as flow visualizations, are performed for the airfoil BAC3-11/RES/30/21. Two models of different chord lengths, 80 and 100 mm, have been used. The maximum Reynolds number achieved to date is 38 x 10 6 for a freestream Mach number of 0.8. The results show that by calibrating the test-section flow carefully, this wind-tunnel technique can generate high-Reynolds-number flows, allowing aerodynamic testing at low cost. The technique avoids the complex cryogenic wind tunnel and model technique, at the expense of relatively short running times and relatively small test-section cross size. The testing time is on the order of 10-15 ms, which is sufficiently long for flow establishment and development of a useful measuring phase with stationary or at least quasi-stationary flow