Nonlinear intrinsic streaks in the flat plate boundary layer

The development of streaky perturbations near the leading edge of a flat plate boundary layer was analyzed by Luchini (1996, [20]) using a description of the flow linearized around the Blasius solution. He found that there is just one single streaky mode (periodic in the spanwise direction) that grows downstream from the leading edge. The presence of this mode in the linear approximation indicates that, for the complete nonlinear problem, there is an one parameter family of streak solutions that grow from the leading edge of the boundary layer. In this work, we numerically compute this family of steady 3D nonlinear intrinsic streaks (intrinsic because they appear in the complete absence of any free stream perturbation). The Reduced Navier–Stokes formulation is used to describe the downstream evolution of this family of Reynolds-number independent, fully nonlinear streaks. The computed nonlinear streaks exhibit a strong spanwise localization, which was not present in their linear counterparts.