Experimental and Computational Aerodynamic Analysis of Low-Re Wings in Translation and Rotation

Experimental validation of computational fluid dynamics (CFD) is critical to ensuring accurate results, especially for complex flow regimes. The current study investigates transition, a standard approach for Vertical Take-Off and Landing (VTOL) aircraft, in which lifting surfaces switch from forward flight to hover, and vice versa. Experimentally, a hybrid reverse wind tunnel system (HRWTS) is employed to simulate the acceleration and rotation of a wing model. This system is used in tandem with CFD efforts to characterize uncoupled acceleration at discrete angles of attack, rotation at constant inflow velocities, and coupled transition, wherein both acceleration and rotational kinematics are combined. Results indicate a strong correlation in the load predictions between the computations and the experiments. CFD results over-predict the loads after stalling. The acceleration rate has a significant effect on the accelerating and rotating wing compared to the wing that is only accelerating. The pitch rate has minimal effects on the rotating and accelerating-rotating wing.