Exploring the Connection between Leading-Edge Suction and Dynamic Stall on Rotors in Forward Flight using Computational Results

Dynamic stall continues to be a limiting factor for rotorcraft performance in forward flight. The complex flow physics, resulting from blade kinematics, aeroelastic deformations, and blade-vortex interactions, makes this problem challenging. The availability of results from recent high-fidelity coupled computational aerodynamics-structural dynamics simulations provides an opportunity to gain new insights into the physics of dynamic stall on rotor blades in realistic operating conditions. Recent research efforts have also resulted in the identification of a leading-edge suction parameter (LESP), whose critical value has been shown to correlate with the flow events leading to dynamic stall. Critical LESP is largely independent of motion parameters, and is dependent mostly on the airfoil shape, Reynolds number, and Mach number. In this work, LESP variation along the blades of a UH-60A rotor in forward flight is extracted from high-fidelity computational results. The objective is to explore the correlation between criticality of LESP and the onset of dynamic stall in a complex rotor flow. The results show a high correlation between LESP behavior and the signatures for the different occurrences of dynamic stall on the rotor blades. This excellent correlation provides the impetus for further application of the LESP concept to rotor aerodynamics.