A large eddy simulation of unsteady argon/steel two phase flow in a continuous casting mold is presented.The Euler-Euler approach has been employed to describe the equations of motion of the two phase flow.The non-drag forces (lift force,virtual mass force) and drag force are incorporated in the model.Large eddy simulation model is used to solve the turbulent viscosity force.Simulation results agree acceptably well with the water model experimental measurements of instantaneous flow structures.The simulation results show that the distribution of the bubble diameter is seen to depend on the argon gas and molten steel flow rates.The mean bubble diameter decreases with increasing the molten steel flow rate,increases with increasing the argon gas flow rate.The asymmetric flow inside the mold was not stationary;the time intervals for changeover appeared to vary randomly.The shape of the bending part of the secondary cooling zone of mold is important to the asymmetric flow.The asymmetric flow occurred near the bending section.