Shallow turbulent wake flows

Shallow turbulent wake flows occur in open channels due to large obstacles like islands or headlands. These flows can generate large-scale quasi two-dimensional vortices that move downstream within a vertical shear flow, influenced by small-scale turbulence from bottom friction. This study employs experimental, analytical, and numerical methods to explore the mean flow and turbulence characteristics of shallow wakes, clarifying the generation and decay mechanisms of large vortical structures and their impact on momentum and mass transport. Part I focuses on non-intrusive optical measurement techniques tailored for shallow shear flows, utilizing a combined LDV-LIF system for high-resolution point-wise flow velocities and mass concentrations, alongside near-surface PIV and depth-averaged PCA systems. Enhanced algorithms for evaluating mass concentrations are based on hydro-optical models. Part II presents a time-mean description of shallow wake flows, revealing a stochastic turbulence field with a spectral distribution of kinetic energy and mass variance that aligns with both large-scale 2D turbulence and small-scale 3D turbulence theories. An integral wake model considering bottom friction is developed and validated with experimental data. Part III investigates the structure and dynamics of quasi-periodic wake flows, emphasizing the role of large-scale eddies through vortex identification and phase-resolved averaging, while emp