On the stability of the boundary layer subject to a wall-parallel Lorentz force

The stability of a transitional boundary layer influenced by a wall-parallel, streamwise oriented Lorentz force is investigated by means of direct numerical simulation. Damping of Tollmien-Schlichting waves is observed already at weak force amplitudes. For a particular amplitude, similar to homogeneous suction, the initial Blasius layer evolves towards an exponential velocity profile of strongly enhanced stability. Here, intermediate velocity profiles are found to have linear stability properties superior to that of the asymptotic exponential profile. Additional three-dimensional simulations support the two-dimensional results as Lorentz forcing clearly damps the coherent structures of the transitional flow. (c) 2006 American Institute of Physics.