Impact of depth-ratio on shear-layer dynamics and wake interactions around wall-mounted prisms

This numerical investigation explores the flow dynamics around wall-mounted prisms with small aspect-ratio (AR=0.25−1.5) and changing depth-ratio (streamwise length, DR=1−4) at a Reynolds number of Re=1000−2500. This study focuses on understanding the formation and evolution of Kelvin–Helmholtz Instability (KHI) and its interactions with coherent wake structures, e.g., hairpin-like vortices. Additionally, it examines the influence of depth-ratio on prism surface pressure distribution and the origin of pressure fluctuations. The results, driven from the extreme geometrical cases of AR=1, DR=1 and 4 at Re=2500, reveal distinct KHI rollers originating from the leading edge shear layer. These impact prism surface pressure distribution and contribute to downstream wake structures. Interactions between KHI rollers and coherent wake structures are more pronounced for larger depth-ratio prisms, leading to a complex wake system. These interactions are quantified using turbulence–mean-shear interaction and turbulence–turbulence interaction from analyzing the Poisson equation. Cross-spectral density analysis highlights the influence of KHI rollers on coherent structures in the wake. These findings emphasize the significance of depth-ratio in shaping prism flow dynamics.