Computational Analysis of Coaxial Rotor Hub Flows and Correlation with Experiment

This study presents computational analyses of coaxial rotor hub flows and validation against experimental data obtained from the rotor hub flow prediction workshops. Experiments were conducted in a 12-in.-diam water tunnel at the Pennsylvania State University Applied Research Laboratory, employing tomographic particle image velocimetry and precise hub drag measurements. The computational fluid dynamics framework which uses an unstructured/Cartesian multimesh paradigm and hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation modeling was applied to replicate and analyze hub flows. Two different hub configurations, consisting of counterrotating hubs, fairings, and shafts, were simulated and compared to experimental results, with a focus on hub drag, wake velocity fields, and turbulence quantities. Results demonstrated that the computational frameworks effectively captured key flow physics, although some discrepancies in drag harmonics, wake velocity, and turbulence intensity magnitudes were observed. Additionally, the study highlighted the impact of rotor hub geometry and installation of a sail fairing on drag and wake structures. These findings contribute to improving computational predictions, essential for designing high-speed rotor hub configurations.