Mean flow and turbulence characteristics around single-arm instream structures

Flow patterns around three widely used instream rock structures in an open-channel flume were investigated using high-resolution large-eddy simulations. Specifically, rock vanes at two different installation angles, a J-hook vane, and bendway weirs at two different angles, with realistic geometries, were studied. Velocity fields in the wake of these instream structures were measured using acoustic Doppler velocimetry, and the measurements were compared with large-eddy simulation results. The computed three-dimensional flow fields were subsequently analysed to investigate and compare the flow patterns for five different cases. The analysis revealed important flow features with regard to three-dimensional flow structure, secondary flow patterns, potential vulnerability to scour, and energy dissipation mechanisms for different cases. The newly discovered flow features provided useful insights into understanding the flow mechanisms associated with instream structures.