Comparison of Computational Fluid Dynamics Hover Predictions on the S-76 Rotor

The S-76 rotor is used as a baseline case to assess the isolated rotor hover predictions of different computational fluid dynamics solvers. These predictions are compared to the available test data as well as to one another. Both grid and parametric studies of the options available within each code are included. The grid studies look into not only blade grid density but also Cartesian and unstructured far-field grid computations and the use of adaptive mesh refinement. A study examining the impact of the hub on the performance predictions is also included. The results show that, in addition to blade-tip grid refinement, leading-edge and trailing-edge grid refinement are important to compute the hover performance. The dual-mesh methodology is shown to preserve the wake for a longer distance when compared to the fully unstructured methodology. This has some impact on the final wake structure. The presence of the hub is found to have a small impact on the final integrated performance parameters. However, there is a greater impact on the convergence rate of these performance parameters as well as the magnitude of the 4/rev time history characteristics. The final integrated performance results obtained from each solver using the best set of grid and input parameters are found to be comparable to one another.