Grid-dependence study for simulating propeller crashback using large-eddy simulation with immersed boundary method

Simulating the flow around a propeller using large-eddy simulation (LES) with the immersed boundary (IB) method is challenging and computationally expensive. In this work, we carry out the grid-dependence study of LES with IB for simulating a propeller in crashback mode using four sets of gradually refined grids. The simulation results show that the grid-resolution requirements for accurately predicting different flow quantities are different. Specifically, it is found that the side-force coefficient and the averaged streamwise velocity are less sensitive to grid resolutions as compared with the thrust force coefficient and the turbulence kinetic energy, respectively. Furthermore, it is found that the computed results in the near wake region and the region around the blade are more sensitive to grid resolutions as compared with the far wake region, where the predictions from the four different grids are similar to each other. This suggests that a coarse grid simulation is adequate if only the far wake region is of interest, while a fine grid simulation is required if one cares about the flow around the blade and the flow in the near wake region.