Lagrangian and Eulerian Perspectives of Turbulent Transport Mechanisms in a Lateral Cavity

The dynamics of the turbulent flows past lateral cavities are relevant for multiple environmental and industrial applications. In rivers and coastal environments, lateral recirculating regions constitute surface storage zones in channels or the shore, where large-scale coherent structures dominate mass and momentum transport, playing a fundamental role in the dynamics of sediments, biogeochemical processes, and nutrient cycles. In this work we carry out LES of the flow in a straight rectangular channel with a lateral square cavity at Re=1.2×10⁴. The model is coupled with an advection-diffusion equation and a Lagrangian particle model to investigate the transport mechanisms in the cavity and across the interface, and to provide quantitative comparisons of these processes from both perspectives.  We also characterize statistically the variables that describe mixing and transport in the flow, analyzing particle trajectories and time scales that describe the mass and momentum exchanges, including residence time distributions and contaminant dispersion. Understanding the small-scale dynamics provides information to improve parameterizations in large-scale models, using statistical analyses that yield new insights of transport mechanisms in environmental flows.