Vorticity Confinement Modeling of Dynamic Stall With Tight Structural Coupling

Dynamic stall is an aerodynamic phenomenon encountered when rotorcraft operate near performance boundaries typical of high-speed or maneuvering flight. The complex, highly non-linear aerodynamics and associated interaction with the structures induce exceptionally high loads, violent vibrations, reduced handling qualities, and a reduction in fatigue life. The prediction of dynamic stall remains one of the most challenging tasks for engineers, necessitating a tightly coupled aerodynamic/structures predictive capability. Comprehensive models are efficient but are generally not valid for a wide range of geometries. Conventional Navier-Stokes approaches have shown promise but their computational cost is prohibitive. Flow Analysis, Inc. (FAI) has developed a technique for predicting dynamic stall using the Vorticity Confinement method incorporated into a compressible flow solver. This approach requires far fewer computational resources when compared to conventional methods. The Vorticity Confinement method has been implemented in the compressible Euler/Navier-Stokes rotor code, Turns_Serial, and used to predict dynamic stall events for the NACA 0015 airfoil, including comparisons with experimental data. A two-degree-of-freedom structural dynamics model has been coupled to the flow solver and stable computations have been demonstrated. A parallel implementation of the flow solver, Turns_Mpi, has been used to demonstrate scalability on a parallel processor for both two- and threedimensional steady computations.