Dynamic Behavior and Gust Simulation in an Unsteady Flow Wind Tunnel

Rapid oscillations of test-section flow velocity can be generated in a wind tunnel using flow-control louvers installed in the wind-tunnel circuit; however, control of the test-section velocity must still account for the dynamic behavior of the wind tunnel itself. In this paper, the dynamic behavior of a low-speed closed-circuit wind tunnel in response to dynamic louver excitation is examined using an experimentally validated method-of-characteristics modeling approach. The model is used to develop and test a method of controlling the louver motions to simulate longitudinal gusts with a von Karman gust spectrum for length scales from 0.1 to 10 m. Results showing improvement of the wind-tunnel dynamic behavior using a Helmholtz resonator are also presented.