Turbulent/Non-Turbulent Interface in a High-Mach Number Boundary-layer Flow

The results of the direct numerical simulation (DNS) of a Mach-4.5 spatially developing boundary layer are used to study the flow characteristics across the turbulent/non-turbulent interface (TNTI). The DNS data is obtained by solving the compressible form of the conservation equations for mass, momentum and energy, and by assuming a calorically perfect gas which is a reasonable assumption at the current Mach number and free-stream conditions. In order to generate realistic turbulent boundary layer, the simulation was performed of an initially laminar, Blasius boundary layer that undergoes transition to turbulence. The Blasius boundary layer is forced at the inflow plane by broadband disturbances obtained from Orr-Sommerfeld and Squire eigenvalue problem, which are introduced inside the region of mean shear only and hence the free stream is irrotational. The transition process is similar to bypass breakdown, where streaks are formed, amplify, and ultimately lead to the formation of turbulent spots that spread and merge together to form the fully turbulent boundary layer. The main objective of this work is to study kinematics and dynamics of the TNTI in a high-speed boundary layer.