DNS of Point-Source Induced Transition in an Airfoil Boundary-Layer Flow

Laminar-turbulent transition induced by a harmonic point source disturbance in a flat-plate boundary layer with adverse pressure gradient is investigated by spatial Direct Numerical Simulation (DNS) based on the complete three-dimensional Navier—Stokes equations for incompressible flow. A local disturbance is introduced into the two-dimensional (2-D) base flow at the wall by a harmonic point source. Thus Tollmien—Schlichting waves of a single frequency and a large number of obliqueness angles are stimulated and propagate downstream simultaneously, undergoing amplification by primary and subsequent instabilities, and eventually lead to breakdown of the laminar flow. The development of the wave train in the boundary layer is investigated by the spectral amplitude evolution and the vorticity/shearlayer dynamics. The computational aspects of this LAMTUR project are discussed in detail for runs on the NEC SX-4 and the CRAY T3E supercomputers.