Helios Adaptive Mesh Refinement for HART II Rotor Wake Simulations

The Helios high-fidelity rotorcraft simulation software is used for CFD/CSD coupling of the HART II rotor-fuselage configuration in descending flight. An unstructured grid solver is applied in the near-body on blade and fuselage, and Cartesian-based unsteady adaptive mesh refinement is applied in the off-body flow field. Comparisons were made for the blade torsion, airloads, wake positions, and vorticity field. Helios predictions were generally comparable to existing state-of-the-art CFD/CSD analysis results. The use of adaptive mesh refinement enabled off-body wake resolution with a grid spacing of 0.025 chords, but the solution was still under-resolved with at least 60% prediction error for the peak vorticity. Diffused tip vortices in the unstructured near-body grid were found to be a significant source of overall wake diffusion, indicating future development of the AMR strategies for the near-body is necessary in order to ensure commensurate resolution between the near-body and off-body meshes.