Forced response of a Blasius flat-plate boundary layer to an external vortex street

An asymptotic theory is presented for two-dimensional disturbances in the wake of an oscillating shedding-vortex line source and in the local presence of a semi-infinite flat plate and its boundary layer. No instabilities were sought or excited. The very large parameter is a Reynolds number; the shedding frequency is moderate. The boundary layer is comprised of three sublayers. In the outer 'edge' sublayer, where the Blasius variable is logarithmically large, the disturbance velocities are described analytically by Kelvin functions. Results compare qualitatively with previous numerical and experimental findings and indicate that the boundary layer effectively suppresses the external disturbances. Those disturbances that remain in the boundary layer peak at a finite (large) Reynolds number and finite frequency.