3.1. Computational grids Fig. 3 shows the CFD and FEM grids for the FSI simulation of the impeller. The CFD grid was generated by ANSYS TurboGrid (Fig. 3a), which has a built-in multi-block mesh topologies for the turbomachinery geometries. Near wall spacing was kept in the range of y + values from 30 to 100 over most of the walls. The FEM unstructured grid was generated using ANSYS Meshing (Fig. 3b). The grid sensitivity study was performed by checking the change of polytropic efficiency and impeller maximum stress with the increase of grids’ number, which are shown in Fig. 4. The results showed those good grid independencies, differences between grids below 0.2%, are obtained with the 1.2M and 1.1M grids for the CFD and FEM simulation, respectively