Assessment of the Vortex Particle-Mesh Method for Efficient LES of Hovering Rotors and their Wakes

Midway between a vortex method and a grid-based CFD, the Vortex Particle-Mesh method with Immersed Lifting Lines is intended to provide medium-fidelity results on rotor loadings, together with a realistic representation of the 3-D vortical wakes and their dynamics over long distances. We assess the potential of this hybrid approach for the Large-Eddy Simulation of helicopter rotors in hover. A novel Poisson solver with mixed unbounded-outflow boundary conditions here further enables the computation of turbulent hovering scenarios in tight domains. Considering the Knight and Hefner experiment and the S-76 test case as references, we present and compare blade integrated and distributed loads, induction velocities, and wake characteristics. While the quality of the performance predictions highly depends on external polar data, the obtained wakes exhibit similar characteristics to those recently identified in other CFD analyses, here at a moderate computational cost. Based on these results, we further investigate the secondary vortex structures forming between the main tip vortices, and we bring additional clues on their relation to the phenomenon of wake breakdown. We finally discuss the strengths and difficulties of hybrid vortex methods for the challenging analysis of hovering rotors.

Affiliations

UCLouvainSST/IMMC/TFL - Thermodynamics and fluid mechanics

Citations

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Caprace, D.-G., Winckelmans, G., & Chatelain, P. (2021). Assessment of the Vortex Particle-Mesh Method for Efficient LES of Hovering Rotors and their Wakes. AIAA Scitech 2021 Forum. Published. AIAA Scitech 2021 Forum, VIRTUAL EVENT. https://doi.org/10.2514/6.2021-0738