Direct Numerical Simulation Of Magnetohydrodynamic Turbulent Flows

Numerical simulation of magnetohydrodynamic turbulent duct flow is crucial in the continuous casting of steel and the application of liquid metal fusion blanket.In the process of continuous casting of steel,where different magnetic field configurations are used to control the turbulent flow of steel in the mold in order to minimize defects in the steel.It will generate magnetohydrodynamic effect(often abbreviated as MHD)when a magnetic field is applied to a liquid metal(LiPb)turbulent flow field in blanket of thermonuclear fusion reactor,then the velocity field can be altered and it has a great impact on heat transfer of liquid blanket.Therefore,the studies of the MHD turbulent flow take a important role in the development of liquid mental blanket concept.Turbulence is one of the most complex flows that commonly exist in the nature,and also most problems in engineering fluid are about turbulence.With the development of experimental and numerical simulation study of the metal fluid MHD effect,people focus in the study also from laminar gradually transferred to the more common in nature and engineering on the turbulence model.However,the study of the mechanism of turbulence and MHD turbulence numerical simulation method are still in the exploratory stage.Direct numerical simulation(abbreviated as DNS)no need to create a turbulent model,but to numerically solve the control equations of flow directly,and this method will calculate all kinds of eddy in flow region.Theoretically,DNS is an ideal numerical calculation method in theoretical research because all the information of flow field and process of real-time evolution about flow can be obtained through DNS.Therefore,present study will adopt DNS method to do research on magnetohydrodynamic turbulent flows.Firstly,we developed a magnetohydrodynamic turbulent flow solver with low magnetic Reynolds number in open source CFD software toolbox called OpenFOAM and validated the accuracy of solver through the case with magnetic field and case without magnetic field.Then,hydrodynamic turbulent flow and magnetohydrodynamic turbulent flow with different parameters in a 2?×1×1 square duct have been simulated by DNS method that through the validated turbulent solver.The distribution of instantaneous velocity and average velocity on the cross section have been presented,and captured the high and low speed region belt of flow velocity in Yplus = 10.The distributions of the root mean square value of perturbation velocity and turbulent kinetic energy along bisector of the cross section have been also presented.The impact of magnetic field on vorticity of cross section is analyzed and the current streamline figures of turbulent and laminar flow on the cross section has been compared.The numerical results showed that the applied external magnetic field has a significant suppression effect on MHD turbulent fluctuation and with the strengthening of magnetic field intensity the suppression effect is more obvious,until the turbulence evolved into laminar flow.At the same time,the suppression effect is anisotropic significantly.