The Interaction of Turbulent Spots with Low-Speed Streaks

Turbulent spots are regions of turbulence surrounded by laminar flow that appear during the late stages of boundary layer transition. While turbulent spots are often studied in isolation, they usually occur near low-speed streaks and other disturbances during transition. This paper investigates the interaction between a turbulent spot and a subcritical low-speed streak using direct numerical simulations. The results, analyzed from streak instability and vorticity points of view, reveal mechanisms of the destabilization of the streak by the spot and provide insights into spot evolution in a realistic environment. Additional simulations involving intentional local control of portions of the streak provide further insight into the interaction mechanisms and potential transition mitigation strategies.