Dynamic Pressure Improvements to Closed-Circuit Wind Tunnels with Flow Quality Analysis

Abstract

Testing of aerodynamic loads on a sub-scale model has been the most accurate way to predict full-scale loads for many years. Even with modern advances in computing technology and computational fluid dynamics (CFD), each computer-aided model must be calibrated against a known standard, usually found through wind tunnel testing. Because wind tunnel testing is usually performed on sub-scale models, flow speeds that span the flight envelope are commonly tested. Traditionally the Texas A&M Engineering Experiment Station Low-Speed Wind Tunnel (LSWT) was limited through available power to a dynamic pressure of 120 psf. The addition of a higher power motor, construction of a new, smaller test section, diffuser liners to prevent flow separation, and increased structure to withstand higher static pressures allows for flow speeds up to 240 psf, nominally Mach 0.4. With proper design and construction, flow quality can be maintained to less than 1% deviation from mean flow velocity. Additionally, an accurate prediction of flow speed for a given test section geometry and power draw can be found.