By considering water and viscous oils respectively as transported fluids,CFD software was used to simulate the fluid dynamics of the whole pump.The effect of liquid viscosity on the pump performance was particularly addressed,and dimensionless angular velocity and leakage rate were investigated in sidewall gap.The results were compared with the experimental data.The results show that the pump lift,flow rate and efficiency are seriously reduced when the viscous fluid is transported.Under the condition of small flow rate,the influence of viscosity on pump performance is less than that under the design condition and under large flow condition.Increasing viscosity improves the volumetric efficiency by reducing internal leakage through wear rings and balance holes.Due to the obvious decrease of the dimensionless rotational angular velocity of the cover plate,the friction loss of the disc increases significantly with the increase of viscosity.The results lead to some recommendations for designing centrifugal pumps which may be used in transferring viscous fluids.