Numerical and Experimental Realization of an Infinite-Swept-Wing Boundary-Layer Flow in a Wind Tunnel

Abstract

Transition to turbulence in boundary layer flows is a process involving several steps: receptivity to ambient disturbances, linear and non-linear disturbance growth, non-linear breakdown and turbulent spot or wedge formation and growth, and finally the establishment of the fully turbulent boundary layer. Ambient disturbances may be in the form of free stream turbulence or sound, but also vibrations of the surface as well as surface roughness may have a distinct role in setting up the initial conditions for further disturbance development. The details of the transition process depend on if the base flow is two- or three- dimensional, whether the flow is subjected to a pressure gradient (favorable or adverse) or not, and if the surface has a curvature (convex or concave) or is flat. Although many steps in the process of these different cases are fairly well understood, the receptivity is in all cases the least researched as well as least understood mechanism, despite the fact that it defines the starting point for the further development of the disturbance field.