Comparison of Computational and Experimental Hub Drag Breakdown for A Scaled Coaxial Counter-Rotating Hub

A computational investigation of aerodynamic drag of coaxial rotor hubs is performed and compared with test data from a prior experiment. The counter-rotating coaxial hub model considered is based on a rotor design developed by AVX Aircraft Company. Component-level contributions to overall hub drag are quantified by building up the rotor from a bare shaft to complete hubs and control systems and measuring the drag as components are added. Fifteen total configurations are considered with CFD and compared to the experimental drag measurements of ten configurations from prior wind tunnel test data. The drag of each hub configuration is presented relative to a baseline configuration featuring the complete coaxial rotor hub and control system without the blade fairings. The CFD results and experimental data verify that the total hub drag is reduced by 25%-29% by incorporating the blade fairings. Nearly half of the remaining drag is from the mast and pitch links, while the blade grip contributes another 25% of the overall drag. The CFD results also show high level of interference drag (9.95%) which includes aerodynamic interference between mast/split plate, upper/lower swash plates, and swash plate/split plate.