<p>The water and sand can have violent interactions in flushing in which the free surface and water–sand interface both experience fragmentation and severe deformation. In this study, the EI-MPS method (explicit incompressible version of moving particle semi-implicit/simulation) is employed to simulate water–sand interactions. This study aims to further validate the EI-MPS method in simulating the flushing flow and to investigate the flushing rate in a tank by the numerical method. To validate the numerical method, the flushing flow in a tank is simulated with different particle distances and similar free surface and water–sand interface profiles are obtained in good agreement with experimental measurements. The initial water height and depth of the sand layer in the tank are respectively examined in the flow to calculate the flushing rate. It is found that the water–sand interface has violent variation in the flow. The flushing rate of the sand layer increases sharply in the early stage of the flow and then gradually approaches a constant level. When keeping the initial water height constant, the shallower sand layer can be flushed easily with larger flushing rates.</p>