Boundary Layer Receptivity to Sound: Navier-Stokes Computations

Here we discuss the computational modeling of the receptivity of the laminar boundary layer on a semi-infinite flat plate with an elliptic leading edge. The incompressible flow is computed in a spatial simulation using the full Navier-Stokes equations in general curvilinear coordinates. Finite differences are used in both space directions and in time. First, the steady basic state is obtained in a transient approach using spatially varying time steps. Then, small-amplitude acoustic disturbances of the freestream velocity are applied as unsteady boundary conditions, and the governing equations are solved time-accurately to evaluate the spatial and temporal developments of instability waves (Tollmien-Schlichting waves) in the boundary layer. A sharper leading edge is found to be less receptive to freestream disturbances.