This study employs direct numerical simulations to investigate wake-induced laminar-to-turbulent transition in separated laminar boundary layers (SLBs) at a moderate gap ratio ($s=0.9$) with ${\text{Re}}_D=800,1575,3900$, and ${\text{Re}}_{\theta }=150$. We characterize the transition process, driven by coherent vortex dynamics synchronized with cylinder wake shedding, through detailed analysis of mean flow, Reynolds stresses, and spatial evolution of velocity spectra. Remarkably, turbulence emerges at such low ${\text{Re}}_{\theta }$ because the transition process follows a hybrid pathway that combines SLB instability and wake-driven $\mathrm{\Lambda }$-vortex formation. The transition unfolds in distinct stages: linear disturbance amplification, nonlinear saturation via superharmonic resonance, and turbulent breakdown. Unlike classical SLB transitions, the wake's periodicity imposes unique spectral signatures on transition dynamics. These findings characterize wake-boundary interactions inherent to turbomachinery and aerodynamic systems, offering insights for potential flow control strategies.

Close

PrevNext

View figure in article

• Transition to turbulence
• Turbulent boundary layers
• Vortex dynamics
• Direct numerical simulations