Comparison of Several Subgrid-Scale Models for Large-Eddy Simulation of Turbulent Flows in Water Turbine

Abstract

Subgrid-scale (SGS) models for large-eddy simulation (LES) define the formalism of an effective eddy-viscosity model. The aim of this work is to quantify and compare different SGS models with experimental data. The first model investigated here is Smagorinsky model (SM), which is the earliest SGS model employed in LES, and given the Smagorinsky coefficient. The second model is dynamic model (DM), which has represented a great improvement in LES, and the coefficient is obtained dynamically. The third model is wall-adapting local eddy viscosity model (WALE), which based on the square of the velocity gradient tensor and has a proper near wall behavior. The last model investigated here is scale-dependent dynamic model (SDDM), which does not rely on the assumption that the model coefficient is scale invariant. The model is based on a second test-filtering operation which allows us to determine from the simulation how the coefficient varies with scale, but it was only validated in atmospheric boundary layer. The finite volume method is used to discretize the turbulence equations on a staggered grid system. The SMPLEC algorithm is used to solve the discrete turbulence equations. Body-fitted coordinates are used to simulate flows over complex geometry fields. The case here investigated are four SGS model of a three-dimension turbulence flows in 90°curved duct at Re = 40000. Finally, we find that the WALE model’s results agreed well with experimental results, indicating that the model and the calculated results are reliable. Meanwhile, the dynamic model also has an acceptable behavior to simulate turbulent flow, but its behavior is not as good as the WALE model, and better than Smagorinsky model. However, the SDDM has a bad performance to simulate turbulent flows of complex geometries. Therefore, the WALE model and dynamic model are applied in water turbine simulations.