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Under the condition of large flow rate and low water level, the free surface vortices vortex is easy to appear in the open intake, which will develop into suction vortices when it is serious, affecting the safe and stable operation of pump station. In order to accurately simulate the flow structure of the vortex, the S-CLSVOF method was adopted for capturing the water-air interface and the VLES, one of the hybrid RANS/LES methods, was used to resolve the turbulence. The effects of mesh and computational time on the results were analyzed in detail, together with the characteristics of the VLES model. The results showed that the VLES model can accurately predict the velocity distributions in the air-entrained vortex flow field. The effect of different grid order of magnitude on the velocity distribution and relative air-entrainment rate was small. To decrease the required computational resources, it was recommended to adopt the mesh with an order of magnitude equals to O(106). According to the variation of relative air-entrainment rate with time, the time when the air-entrained vortex reached stability can be judged. After that, another computation of 10s was necessary to satisfy the corresponding standard for clearly identifying the free surface vortex. Further prolonging the calculation time did not change the variation of the position of the air-entrained vortex and the relative air-entrainment rate. In this case, the resolution of VLES was mainly affected by the turbulent integral length scale. In the near wall region, VLES behaved as RANS to decrease the demand on the mesh resolution near the wall, while in the turbulence core region, it turned to hybrid RANS/LES to increase the accuracy of the simulation. The research results can be used to guide the simulation of the air-entrained vortex in hydraulic intakes.