A dynamic particle scale-driven interphase force model for water-sand two-phase flow in hydraulic machinery and systems

Abstract

The water–sand two-phase flow in hydraulic machinery and systems has a strong inter-phase interaction due to the effect of rotating turbulence, but many engineering computations do not consider turbulent effects into the interphase force, affecting the prediction accuracy of inner flow characteristics. The objective of this paper is to provide a new dynamic particle scale-driven interphase force model, and its notable features are shown as follows. In the Euler-Euler framework, the time-scale-driven hybrid URANS/LES model is introduced to extend the resolution scale of rotating turbulence. On this basis, (1) the turbulent factor and the wall factor based on a dynamic particle scale are determined to reflect the effects of turbulent fluctuation and wall surface on the drag force; (2) a new turbulent dispersion force model based on a dynamic particle scale is proposed to characterize the following behavior of heavy particles and their interaction with energetic eddies. Four typical flow cases of sediment-laden flows are tested. It is found that the eddy viscosity of water turbulence is effectively adjusted, thereby allowing more turbulent vortices to be resolved on the same URANS grids. The settling motion and inertial motion of sand are reasonably controlled by the improved interphase force model, thereby giving the prediction results of two-phase flow fields with higher accuracy. The new model improves the simulation accuracy of water–sand two-phase flow with rotation and curvature while does not significantly increase the computational cost, which enables efficient engineering computations of water–sand two-phase flow in hydraulic machinery and systems.