Localized drag modification in a laminar boundary layer subject to free-stream travelling waves via critical and Stokes layer interactions

Perturbation of the laminar boundary layer by free-stream travelling waves was shown to produce highly-localized skin friction modification via steady streaming. The forced flow calculated numerically and studied as a function phase speed, frequency amplitude perturbations. Upstream-travelling always produced negative streaming, whereas downstream-travelling positive or streaming that varied with forcing strength streamwise location. sign resultant explained in terms inclination induced velocity modes, which evolved spatially response variation overlap Stokes critical layers.