The Frank J. Seiler Research Laboratory (FJSRL) at the U.S. Air Force Academy is conducting a comprehensive experimental research program to study unsteady, separated flows and, in particular, the dynamic stall of oscillating airfoils. The aim of this study is to achieve a clearer understanding into the physical mechanisms responsible for dynamic stall and to capitalize on these unique stall features by using them to improve the turn performance and maneuverability of flight vehicles. The objective of one phase of this experimental research program has been to adapt a general purpose Laser Doppler Velocimetry (LDV) two velocity component system to dynamic stall experiments in the Subsonic Wind Tunnel at the USAFA. The preliminary design of the LDV system, its special constraints and the characterization of system signal and noise parameters are described. Results presented for the initial operation of the LDV system demonstrate its performance capabilities. It has been observed that accurate measurements in the wind tunnel environment can be achieved only when optical noise produced by scattered laser light from wind tunnel surfaces is minimized. While the LDV system configuration satisfies all constraints related to the USAFA Subsonic Wind Tunnel geometry and is capable of accurate velocity measurements in the two-dimensional flow field surrounding an airfoil, a reconfiguration of the system is suggested to improve optical alignment procedures and overall system signal-to-noise ratio. (Author).

Project 2307. ADA061724.