Numerical investigation of magnetohydrodynamic mixed convection over an isothermal circular cylinder in presence of an aligned magnetic field

• Mixed convection MHD flow around a cylinder is investigated.
• Magnetic field is used to control the wake region and heat transfer.
• High Pr fluid is better controlled when compared to a low-Pr fluid.
• Drag coefficient varies non-monotonically with Pr.
• Mean Nusselt number has a non-monotonic behavior with the magnetic field.

The influence of magnetic field on the steady, laminar flow of an incompressible and electrically conducting fluid with mixed convection over a circular cylinder subject to uniform surface temperature is analyzed. The governing nonlinear Navier–Stokes equation with buoyancy body force term, coupled with temperature given by energy equation are solved by using a high order finite difference scheme in cylindrical polar coordinates without imposing axis of symmetry and employing quasi-static approximation. Numerical solutions for the flow and temperature fields are obtained for low Re   and the effect of magnetic field on the flow structure and heat transfer is discussed. The vortex structure, in the absence of magnetic field, is symmetric in forced convection flows whereas in the mixed convection cases, the symmetry is broken. The applied magnetic field, in turn, opposes the symmetry breaking and tries to restore a nearly symmetric flow about θ=0θ=0 line. The total drag coefficient non-monotonically increases with increasing Prandtl number. Heat transfer is analyzed by computing the surface and mean Nusselt numbers and the behavior of local Nusselt number is explained. The mean Nusselt number monotonically increases with Ri and Pr whereas it exhibits non-monotonic behavior with applied magnetic field strength.