The effects of different synthetic eddy disturbances on boundary layer transition in high speed flow

This study employs Large Eddy Simulation (LES) to investigate the impact of initial synthetic eddy disturbances on the nonlinear transition process and turbulence characteristics within a boundary layer at a Mach number of 2.25. This study examines the influence of synthesized eddies with varying rotational directions, turbulence intensities, and spatial sizes on the boundary layer transition process and the characteristics of the post-transition flow field. Significant differences are observed in the transition starting position, high friction resistance region, and downstream turbulent pulsations among eddies with distinct parameters. Eddies with different rotational directions initiate transition at the same position and conclude at the same location. In contrast, the beginning of the transition of synthetic eddies with lower turbulence intensity is significantly delayed, although the length of the transition interval remains approximately equal across different turbulence intensities. Large-scale eddies can effectively induce rapid boundary layer transition but also lead to pronounced local peaks in surface friction and heat flux. This characteristic is detrimental to thermal protection in regions where heat flux is prone to overshoot.