Numerical analysis of boundary layer transition caused by asymmetric cavities.

Abstract

The transition of the boundary layer to turbulence has significant implications in engineering due to the higher coefficient of friction exhibited by the turbulent boundary layer compared to the laminar boundary layer. Recent research by our group has investigated the boundary layer transition process induced by surface gaps, a crucial analysis of the transition phenomenon, since cavities are present in most aerodynamic equipment. Results obtained by the group highlighted the essential role of the interaction between two-dimensional unstable modes (Rossiter modes) and three-dimensional unstable modes (centrifugal modes) in inducing the transition process to turbulence. In this project, I evaluate asymmetric rectangular cavity configurations, i.e., with trailing edge at a different height than the leading edge. In the study, I use computational calculations with a direct numerical simulation (DNS) of the compressible Navier-Stokes equations and apply linear stability analysis of two- and three-dimensional modes calculated by linear stability theory (LST) using an in-house code developed by this research group. The code uses an Arnoldi-based time-stepping method, which allows the complexities of the phenomenon of LST analysis to be accurately represented. Preliminary analysis revealed that varying the trailing edge height affects the interaction between the two-dimensional mode and the mixing layer of the flow. Thus, controlling the trailing edge height allows controlling the stability of the flow over the cavity.