Control of Flow Separation Around Bluff Obstacles by Transverse Magnetic Field

Abstract

Electromagnetic fields may be used to control the flow separation during the flow of electrically conducting fluids around bluff obstacles. The steady separated flow around bluff bodies at low Reynolds numbers almost behaves as a creeping flow at a certain field strength. This phenomena, although already known, is exactly quantified through numerical simulation and the critical field strength of an externally applied magnetic field is obtained, for which the flow separation is completely suppressed. The flow of a viscous, incompressible, and electrically conducting fluid (preferably liquid metal or an electrolyte solution) at a Reynolds number range of 10–40 and at a low magnetic Reynolds number is considered in an unbounded medium subjected to uniform magnetic field strength along the transverse direction. Circular and square cross sections of the bluff obstacles are considered for simulation purposes. Fictitious confining boundaries are chosen on the lateral sides of the computational domain that makes the blockage ratio (the ratio of the cylinder size to the width of the domain) 5%. The two-dimensional numerical simulation is performed following a finite volume approach based on the semi-implicit method for pressure linked equations (SIMPLE) algorithm. The major contribution is the determination of the critical Hartmann number for the complete suppression of the flow separation around circular and square cylinders for the steady flow in the low Reynolds number laminar regime. The recirculation length and separation angle are computed to substantiate the findings. Additionally, the drag and skin friction coefficients are computed to show the aerodynamic response of the obstacles under imposed magnetic field conditions.