Simulation of Gust Generator-Induced Wind Tunnel Flow Fields

Abstract

A mathematical/numerical investigation was carried out of the flow characteristics of wind tunnel test section flow influenced by a gust generation system. The University of Washington's 3'x3' Low-Speed wind tunnel was modeled using high-fidelity Computational Fluid Dynamics (CFD) simulations and using easy-to-program and inexpensive-to-run vortex lattice methods (VLM). Steady and unsteady CFD flow simulations were completed to study the nature of the flow field created by the gust generator in the wind tunnel. The gust generator induced gust angle-of-attack and the velocity of the flow field at various locations in the test section were determined and the aerodynamic effect on a test wing was also studied. In the time marching vortex lattice method developed, accounting for the effect of the walls of the wind tunnel on the forces felt by the test object was done via a system of mirror images. The VLM simulations were compared to classical Theodorsen solutions and to the CFD simulations to gauge the accuracy of the VLM simulations. In the presence of wind tunnel walls, the VLM simulations overestimated the forces felt by the test object when compared to the force predictions of the CFD simulations, but overall captured the time behavior well. Knowing the magnitude of difference between CFD and VLM results, VLM simulations can still be a useful tools, fast and inexpensive, for the design of wind tunnel gust generation systems and the positioning of wind tunnel models relative to them.