Large Eddy Simulations Of Magnetohydrodynamic Turbulent Insulated Duct Flow

In the liquid metal blankets of thermal nuclear fusion reactors,there will be magnetohydrodynamic(MHD)effects generated due to an external magnetic field.And this MHD effects can change the flow situation in the tube.Thus has a great influence on the heat transfer of the liquid cladding in the reactor.Therefore,the study of the magnetic fluid turbulence has a great effect on the development of liquid metal cladding concept.In recent years,MHD effects on the liquid metal in the cladding has been greatly developed.And the focus of the study has also been shifted from laminar flow to turbulent flow,which is more general in nature and engineering.In this paper,large eddy simulation(LES)has been used to study the flow of metal fluid in the square tube because the direct numerical simulation(DNS)has high requirements on the grid and the calculation of DNS is relatively large.Recent studies have revealed that the dynamic Smagorinsky model(DSM)performs well in the simulation of turbulent flow.Therefore,this paper use three SGS models(DSM,Smagorinsky model(SM)and dynamic one equation model(DOM))to simulate magnetic fluid flow in order to disscussed its performance in MHD flows.Based on the open-source CFD software OpenFOAM,a low-magnetic Reynolds number LES for magnetohydrodynamic turbulence has been developed.And the performance of the solver at low Reynolds number and high Reynolds number has been studied respectively.Then,the average velocity,the root mean square of the velocity and the turbulent kinetic energy distribution has been compared.It is found that the DSM performed better than the other two models.Then the effect of magnetic field on the MHD turbulent flow are analyzed by comparing the mean velocity,the root mean square velocity and the turbulence kinetic energy.Then the influence of magnetic field intensity on the turbulence of the magnetic fluid is studied.The result shows that the applied external magnetic field has a significant suppression effect on MHD turbulent fluctuation.And with the enhancement of magnetic field intensity the suppression effect will be more obvious until the turbulent flow evolved into laminar flow.At the same time,the suppression effect is anisotropic significantly.At last,Wall friction coefficient has been used in order to study the transformation mechanism from laminar flow to turbulent flow.