Large-eddy simulation of separated turbulent flows over a three-dimensional hill using WRF and OpenFOAM

It is not clearly known about the limitations of the large-eddy simulation (LES) mode of an atmospheric model (WRF) in predicting the microscale flows for engineering purpose. This study chooses a typical separated turbulent flow past a three-dimensional axisymmetric hill and investigates the performance of WRF-LES in comparison with the popular CFD solver (OpenFOAM). The numerical models and conditions are set similarly between the two codes. The instantaneous visualization shows that both WRF-LES and OpenFOAM-LES can produce the primary flow features, including hairpin vortices, horseshoes, and surface-shear-induced vortices at different scales, with high similarity. Nevertheless, the turbulent kinetic energy in the near wake produced by WRF-LES is underestimated, in comparison with WRF-LES. The energy spectra suggest that WRF-LES using the high-order advection schemes has a stronger capacity of generating and maintaining small-scale turbulent motions than OpenFOAM-LES. Furthermore, the deviation of numerical dissipation behavior is examined between the two solvers.

Automated summary

The limitations of large-eddy simulation (LES) mode in predicting microscale flows for engineering purposes in an atmospheric model (WRF) are not well understood. This study compared the performance of WRF-LES with the popular CFD solver (OpenFOAM) using a typical separated turbulent flow past a three-dimensional axisymmetric hill. The results showed that both models were able to produce the primary flow features with high similarity, but WRF-LES underestimated the turbulent kinetic energy in the near wake compared to OpenFOAM-LES. The energy spectra suggested that WRF-LES had a stronger capacity for generating and maintaining small-scale turbulent motions than OpenFOAM-LES. Additionally, the deviation of numerical dissipation behavior between the two solvers was examined.