Effect of yaw angle on aerodynamics of square inclined flat plates in ground effect

Abstract

Aerodynamics of finite-span inclined square flat plates is experimentally investigated at a chord-based Reynolds number of 50 000 in ground effect. The minimum ground height is varied between gap ratios of 0.1 to 1.0 in chord lengths. All components of forces and moments are measured using a load cell for yaw angles between 0° and 180° at an angle of attack of 30°. In addition, surface flow visualization and planar, three-component particle image velocimetry are used to relate the main trends in structural loadings to changes in flow development. The results show that ground effect is significantly modified by yaw angle. As the gap ratio is decreased, a relatively invariant suction side flow and moderate increase in total force and moment driven by ram effect are observed for yaw angles less than 90°. Between yaw angles of 90° and 120°, the suction side flow is also insensitive to gap ratio variations, however, the loading is constant due to absence of ram effect. The suction side sting placement resulted in notable sting effect on both loading and flow for yaw angles between 120° and 150°, obfuscating the impact of ground proximity. For yaw angles above 150°, the onset of stall with decreasing gap ratio leads to a decrease in total loading, with the effect becoming more pronounced at higher yaw angles. These results may be utilized to drive targeted designs of photovoltaic support structures based on site surveys of wind direction and ground clearances.