Study On The Influence Of Magnetic Field On The Flow And Heat Transfer Around A Circular Cylinder

The problem of the flow around a cylinder has always been a classical problem in fluid mechanics,which is widely used in the field of wind resistance of high-rise buildings and marine engineering.In history,Carmen Vortex Street has caused great losses to all countries.In order to avoid the impact of Carmen Vortex Street on buildings,after a lot of research by researchers,the mature way to eliminate Carmen Vortex Street behind a cylinder is to change the shape of the cylinder or apply Lorentz force to the fluid field.However,there are few papers to study the influence of magnetic field to remove the Carmen Vortex StreetAiming at eliminating Carmen Vortex Street behind a circular cylinder,the effect of magnetic field force on suppressing Carmen Vortex Street is observed and the change of flow field structure under different Reynolds number and different residual magnetic field intensity is studied in this paper.Besides,in order to get the best relationship between the residual magnetic field intensity and the heat transfer on the cylinder surface,the heat transfer on the cylinder surface under different residual magnetic field intensity is also analyzed.In this paper,ANSYS was used to calculate the magnetic force,CFX was used to calculate the flow field,where the unidirectional coupling between ANSYS and CFX was realized.The results show that the magnetic field force can eliminate the Karman vortex street behind the cylinder.When the Reynolds number is constant,the magnetic field force is not enough to restrain the Karman vortex street behind the cylinder when the residual magnetic field intensity is 0.5T;When the residual magnetic field intensity is 1T,the magnetic field force has a powerful restraint effect near the cylinder while the poor restraint effect away from cylinder;When the residual magnetic field intensity is increased to 1.5T,the magnetic field can completely suppress the Karman vortex street,where the jet phenomenon is appeared obviously behind the cylinder.With the increase of the residual magnetic field intensity,the retention zone behind the cylinder decreases gradually until it disappears.With the increase of magnetic field intensity,The average Nu on the cylinder wall decreases first and then increases.The larger the Re is,the lower the Nu minimum is,and the Nu minimum value is in the transition state of magnetic force restraining Karman Vortex Street.Under the same Re,with the increase of magnetic field intensity,the heat transfer effect of fluid at the upper and lower walls of the cylinder is the best and the heat transfer effect of the front stagnation point is better than that of the back stagnation point,which is the worst heat transfer effect.With the increase of magnetic field intensity,the drag coefficient of fluid decreases gradually.The smaller the Re is,the faster the drag coefficient decreases and the larger the Re is,the slower the drag coefficient decreases.When the magnetic field intensity increases from 0 to 3.5T,Re=50.the fluid drag coefficient decreases from 2.17 to-4.88,which decreases by 324.88%,while the fluid drag coefficient of Re=300 decreased from 1.63 to 1.20,which decreases by 26.38%.