DNS of Laminar-Turbulent Transition in Swept-Wing Boundary Layers
Direct numerical simulation (DNS) is performed to examine laminar to turbulent transition due to high-frequency secondary instability of stationary crossflow vortices in a subsonic swept-wing boundary layer for a realistic natural-laminar-flow airfoil configuration. The secondary instability is introduced via inflow forcing and the mode selected for forcing corresponds to the most amplified secondary instability mode that, in this case, derives a majority of its growth from energy production mechanisms associated with the wall-normal shear of the stationary basic state. An inlet boundary condition is carefully designed to allow for accurate injection of instability wave modes and minimize acoustic reflections at numerical boundaries. Nonlinear parabolized stability equation (PSE) predictions compare well with the DNS in terms of modal amplitudes and modal shape during the strongly nonlinear phase of the secondary instability mode. During the transition process, the skin friction coefficient rises rather rapidly and the wall-shear distribution shows a sawtooth pattern that is analogous to the previously documented surface flow visualizations of transition due to stationary crossflow instability. Fully turbulent features are observed in the downstream region of the flow.
L. Duan et al., "DNS of Laminar-Turbulent Transition in Swept-Wing Boundary Layers," Proceedings of the Center for Turbulence Research Summer Program, 15th (2014, Stanford, CA), United States. National Aeronautics and Space Administration, Jun 2014.
Center for Turbulence Research Summer Program, 15th (2014: Jul. 6-Aug. 1, Stanford, CA)
Mechanical and Aerospace Engineering
Center for High Performance Computing Research
Article - Conference proceedings
© 2014 Duan Lian; Choudhari, Meelan M.; Fei Li, All rights reserved.