Transition under elevated free-stream turbulence

Elevated free-stream turbulence accelerates the process of laminar-to-turbulent transition by the selective inclusion of low-frequency disturbances into the boundary layer. As these amplify, they form longitudinal streaks that rapidly break-down into localized regions of turbulence that resemble the turbulent spots studied here under low free-stream turbulence. The manner in which free-stream turbulence alters the spot-growth mechanisms is unclear. Because gas-turbine engine environments and turbomachinery applications involve flows with elevated free-stream turbulence levels, this question is important to answer.