Numerical Simulation Of MHD Effect Of Coaxial Square Tube In Oblique Magnetic Field Title

In fusion reactor,the Liquid Breeder Blankets have the advantages of simple structure design,strong heat transfer ability and easy to produce tritium proliferation and extraction,so it could be the preferred choice for fusion reactor design.However,in the presence of a strong magnetic field,the Liquid Breeder Blankets will have magnetohydrodynamic(MHD)effect.It could lead to the complex flow of liquid metal in the pipeline and produce a pressure drop far greater than that of ordinary hydraulics,which will seriously affect the heat and mass transfer of the fluid.However,in the liquid metal flow,the structure of the pipeline,the conductivities of the pipeline,the direction of the magnetic field,the Hartmann number and other factors will have a great influence on the MHD effect.Therefore,the study of liquid metal flow in strong magnetic field with special structure has very important reference value and significance.In this paper,a multi-physical coupling model based on commercial software COMSOL is used to numerically simulate and analyze the mechanical behavior of liquid metal flow in a coaxial square pipe under an oblique magnetic field.Firstly,this paper analyzes and verifies the multi-physical field coupling model.The dimensionless parameters commonly used in MHD calculation are introduced,and the MHD governing equation of incompressible and viscous Newtonian fluid flow in pipelines are given.On this basis,the analytical solutions of classical MHD cases,Shercliff and Hunt,are derived.After analyzing and comparing with the analytical solution,the accuracy of the calculation model in this paper is confirmed.Then,according to calculating the MHD effect in the square tube under the oblique magnetic field,and comparing with the numerical results in the literature,the applicability of the program is determined,and it can be used to calculate and analyze the complex MHD problems in the oblique magnetic field.Furthermore,the MHD effect in the coaxial square pipe is simulated under different magnetic field angles,and it is found that the velocity distribution in the pipe changes with the change of magnetic field angles.When the magnetic field angle is zero,there are six jets in the inner and outer tubes,of which there are four in the outer tube and two in the inner tube,and their distribution is symmetric along the center line of Hartmann wall.When the magnetic field angle is not zero,six jets also appear in the inner and outer tubes,and the distribution is centrally symmetric.For different magnetic field angles,the direction of jet extension is basically consistent with the direction of magnetic field.The effect of different tube wall conductivities on the liquid metal flow in the coaxial square tube is further analyzed.Finally,on the basis of the above work,the effect of inner tube eccentricity on magnetic fluid flow is studied.The numerical results show that the eccentricity of the inner tube will lead to the change of the peak velocity of the jet.At the same time,the inner pipe eccentricity in different directions has a great difference to the flow in the pipe.It is found that when the inner tube is eccentric in any direction,the velocity distribution in the tube will be offset accordingly.In this paper,the distribution characteristics of velocity,current and potential in coaxial square pipe under different magnetic field angles,different conductivities of inner and outer tubes and different eccentricity directions of inner tubes are studied by numerical simulation.This structure provides certain reference value for the design and development of Liquid Breeder Blankets in the future.