Flat Plate Drag in Magnetohydrodynamic Flow

Abstract

In sub‐Alfvén magnetohydrodynamic flow past a flat plate (the free stream fluid velocity is less than the Alfvén wave speed) the vorticity generated within the fluid is propagated upstream by Alfvén waves and produces a forward disturbance which in form is very similar to the viscous wake. The structure and strength of the wake and precursor are herein examined and compared for large Reynolds numbers and finite conductivity. As the conductivity increases, a larger proportion of the total vorticity is propagated upstream so that the precursor becomes more pronounced and the wake weakens. Explicit formulas for the skin friction and drag coefficient are determined for arbitrary values of the conductivity, and the results clearly exhibit the effects of the interaction of fluid flow and magnetic field.