CFD in rotor-stator cavity. Analysis and testing with three CFD solvers

In CFD accuracy and speeds are the defining characteristics of a code. In this study two numerical methods are considered. One is the pressure-based approach, developed for low-speed incompressible flows, and the second one is the density-based approach for high-speed compressible flows. Both of them are currently applicable to a broad range of flows. In this study an application of a density-based solver for low-speed incompressible flows is shown. This project compares two Rolls-Royce developed CFD solvers, Hydra and PRECISE, against the commercial code FLUENT. Different test cases were analysed for studying the accuracy and the speed of the three codes. The first test case geometry is a generic rotor-stator cavity at Mach 0.35 and Reynolds 10^7. The codes have been benchmarked on the convergence speed using two structured meshes and comparing the moment coefficient calculated on the rotor surface. The set-up was arranged in a similar way among the three codes. For Hydra simulations both an explicit and an implicit algorithm has been tested. The second test case is Daily and Nece’s experiment on an enclosed disk. Two geometries, with different gap sizes between the rotor and the stator, have been analysed. In this test case two rotor speeds have been considered to account for different local Reynolds. Benchmark is the moment coefficient on the rotor measured by Daily and Nece. FLUENT pressure-based solvers perform better in terms of CPU time. The implicit algorithm in Hydra has shown significant improvement with respect to the base line version.