Unconfined Plunging of a Hyperpycnal River Plume Over a Sloping Bed and Its Lateral Spreading: Laboratory Experiments and Numerical Modeling

Hyperpycnal (negatively-buoyant) river inflow into lakes and oceans often develops three-dimensional (3D) plunging flow patterns when laterally unconfined. To determine the 3D pattern characteristics, laboratory experiments of unconfined on a sloping bed were carried out using salinity to control density difference. The complemented by numerical modeling based high-resolution Computational Fluid Dynamics model. As is case for confined plumes, it was found that in plunging, densimetric Froude number Frd-0 at mouth slope receiving water body β are dominant parameters. However, results documented hydrodynamics fundamentally different: hyperpycnal plume configurations forms triangle surface plunge zone due its convergence near lateral spreading bottom. triangular extends further increases or bottom decreases. entrainment coefficient, which quantifies amount ambient entrained plume, also with increasing Frd-0. In general, much higher than plunging. Frd-p takes constant value ∼0.5 whereas can be ≫ 1 Complex secondary currents occur plume. A low-velocity whose size observed centerline above bed. This article protected copyright. All rights reserved.