Evolution of suction parameters on a large-amplitude pitching hydrofoil

The leading-edge suction parameter (LESP) is broadly applied to unsteady aerodynamic models, such as for predicting shear layer separation and leading-edge vortex shedding. The LESP evaluated through partial circulation and its relation to the shear layer dynamics were previously defined and examined in experiments for airfoils undergoing flow perturbations and dynamic stall at moderate to high angles of attack (below 30 degrees). The current study applies this definition to a hydrofoil pitching at large amplitudes (up to 120 degrees) in both quiescent flow and uniform flow conditions. The LESP values calculated from the particle image velocimetry flow field results validate the partial circulation approach in large-amplitude conditions where the shear layer dynamics noticeably differ from those of lower-amplitude cases. The partial circulation and the associated suction parameter are extensively defined and measured at the trailing edge to account for the interaction between the trailing edge and the flow in such large-amplitude circumstances. The relations between the suction parameters and the hydrodynamic loads are studied in a parameter space of variable pitching frequencies and amplitudes.