Cut To Shed Electromagnetic Control Of Flow Around A Cylinder

In this paper, the experimental and numerical investigations on electro-magnetic control of cylinder wake have been performed in this paper. Experiments are conducted in a rotating annular tank filled with a low-conducting electrolyte, the electro-magnetic actuator is made of staggered magnetic and electro. A cylinder with an electro-magnetic actuator mounted on the surface is placed into the electrolyte. Force measurements have been carried out by strain gages attached to a fixed beam to which the cylinder is suspended and flow fields are visualized by dye markers. Based on the Navier-Stokes equations considering the electromagnetic body force, i.e. Lorentz force, in the exponential-polar coordinates, the numerical investigations are carried out by means of an Alternative-Direction Implicit algorithm and a Fast Fourier Transform algorithm. Experimental results have shown the same tendency with the numerical results.The research show that with the uniform flow condition, the electromagnetic body forces, which caused by the electromagnetic field can change the cylinder boundary layer structure and suppress the boundary layer separation. However, the control effect of electromagnetic force is different with different value and different actuator width. When Lorentz force is small, the separation points on the cylinder surface will be moved rearward, but it cannot be suppressed completely. When the Lorentz force become large, the flow separation can be suppressed completely by the narrow actuator first. When the Lorentz force become further large, both the wide and narrow actuators can suppress the cylinder wake successfully.The drag and the values of drag vary will reduce when the Lorentz force become larger.The flow field is symmetrical on the uniform flow condition. Before the application of Lorentz force, the values of lift vary periodically because the vortexes appear and shed periodically from the cylinder. Then, the average value of lift is 0. With the application of Lorentz force, the lift becomes steady because of the suppression of vortex shedding, and its value is 0. However, the shear flow is not symmetrical. If the flow velocity is large on the cylinder upside and small on the cylinder underside, the wake leans to the side of small velocity of flow. The shift of the front stagnation point to the high velocity side, the pressure is large on the high velocity side and small on the low velocity side. The average value of lift is not 0 any longer, and its direction points to the low velocity side. With the action of Lorentz force, the wake becomes a line leaning to the side of low velocity of flow and the lift becomes steady,but the value of lift is not 0. The absolute value of lift becomes larger with the increase of Lorentz force.