Nonlinear equilibrium solutions in a three-dimensional boundary layer and their secondary instability

摘要: The observed nonlinear saturation of crossflow vortices in the DLR swept-plate transition experiment, followed by onset high-frequency signals, motivated us to compute equilibrium solutions for this flow and investigate their instability disturbances. are independent receptivity, i.e. way generated, thus provide a unique characterization prior turbulence. Comparisons these with experimental measurements exhibit strong similarities. Additional comparisons results from parabolized stability equations (PSE) spatial direct numerical simulations (DNS) reveal that become unstable steady, oscillations very long wavelengths following bifurcation close leading edge. Such spatially oscillating have been also critical layer theory computations. nature behaviour is herein clarified shown be analogous encountered temporal simulations. We then employ Floquet systematically study dependence secondary, instabilities on amplitude solutions. With increasing amplitude, most amplified mode can clearly traced spanwise inflectional shear layers occur wake-like portions (Malik et al. 1994 call it ‘mode I’ instability). Both frequency range eigenfunctions resemble recent Kawakami (1999). However, lack an explosive growth leads believe additional self-sustaining processes active at transition, including possibility absolute