Mach effect on instability and transition in flows over gaps

This study investigates the influence of Mach number on instabilities and transition phenomena in flows over gaps. Utilizing direct numerical simulations (DNS) and global stability analysis, we explore the interaction between Rossiter and centrifugal modes in three-dimensional compressible flows. The simulations, conducted at various Mach numbers (0.5, 0.9, 1.2, 2.0, and 3.0), reveal the role of gap geometry and flow parameters in determining instability mechanisms. Results highlight the dependence of acoustic wave interactions and spanwise modulations on Mach number, providing insights into nonlinear interactions between Rossiter and centrifugal modes. These findings contribute to understanding boundary layer transitions over gaps, with implications for aerodynamic drag reduction and flow control strategies.