Laminar-turbulent Transition in a Laminar Separation Bubble in the Presence of Free-stream Turbulence

摘要: Abstract Direct numerical simulations (DNS) are employed to investigate the hydrodynamic instability mechanisms and transition turbulence in laminar separation bubbles (LSBs) on a flat plate. A set of simulat2013-0264ions has been carried out process, particular shed light development large coherent structures, which arise during transition. Particular focus is directed towards understanding identifying relevant physical governing interaction presence free-stream (FST). For natural flow. i.e. zero FST, mechanism involves Kelvin-Helmholtz growth three-dimensional very low-frequency disturbances shear layer. With inclusion accelerated. investigated, process result two different mechanisms: i) Strong amplification high-frequency (order shedding frequency), essentially two-dimensional or weakly oblique fluctuating ii) low-frequency, three- dimensional Klebanoff perturbations caused by FST. Depending intensity one these would dominate both blended together contribute simultaneously.