Effect of yaw angle on aerodynamics of a square inclined flat plate in ground effect*

The aerodynamics of a square inclined flat plate is investigated using flow and force measurements for yaw angles between 0° and 180°. The Reynolds number is 50,000 and the angle of attack is 30°. The minimum clearance between the ground and the plate is varied between 0.1 and 1 chord length. Lift and drag are measured using a load cell. Surface oil flow visualizations provides a holistic view of the highly three dimensional flow development over the suction side, which are accompanied by cross-flow stereo particle image velocimetry measurements at the leeward point of the model. The results reveal strong tip effects at yaw angles of  0° and 180° in free flight, causing leading edge shear layer reattachment over the plate, leading to relatively high lift and drag coefficients. As yaw angle of 90° is approached, tip effects diminish, and the loads decrease under both free flight and ground effect conditions. Ground effect on loading is dependent on the yaw angle and whether the suction or the pressure side is exposed to the ground, with the former experiencing a decrease in forces, while the latter observes an increase in forces with decreasing ground height.