MHD flow and heat transfer in a backward-facing step

The laminar flow of a viscous incompressible electrically conducting fluid in a backward-facing step is investigated under the usual magnetohydrodynamic (MHD) hypothesis. Numerical simulations are performed for Reynolds numbers less then Re = 380 in the range of 0 ≤ N ≤ 0.2, where N is the Stuart number or interaction parameter which is the ratio of electromagnetic force to inertia force. Heat transfer is investigated for Prandtl number ranging from Pr = 0.02 corresponding to liquid metal, to Pr = 7 corresponding to water. It is found through the calculation of the reattachment length that external magnetic field acts to decrease the size of the recirculation zone. Velocity profiles show that, out of the recirculation zone, the basic flow is damped by the magnetic induced force, whereas flow near the walls channel is accelerated. Heat transfer is significantly enhanced by the magnetic field in the case of fluids of high Prandtl numbers.