Numerical Simulation of Crossflow-Transition Control using Pinpoint Suction

Laminar-turbulent transition in swept-wing boundary layers is typically caused by secondary instabilities of steady crossflow vortices (CFVs). So far, suction for laminar flow control (LFC) in three-dimensional boundary layers has been applied to reduce the crossflow and thus the growth of the primary CFV modes to CFVs. We investigate the influence of strong, localized suction (pinpoint suction) on developed high-amplitude CFVs and their secondary instability. By means of direct numerical simulation we show the successful application of pinpoint suction resulting in a significant delay of transition. Strong suction at the wall turned out to require an extremely small wall-normal grid spacing near the wall for our incompressible vorticity-based code N3D. For verification of the results a comparison with our compressible code NS3D has been performed.