Author(s): Haoran Shi; M. E. Negretti; J. Chauchat; K. Blanckaert; U. Lemmin; D. A. Barry
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Keywords: River plume; Shear layer; Coherent structures; Buoyancy
Abstract: River flow usually brings large amounts of nutrients, pollutants and sediments when it enters a lake. In the nearfield, it undergoes various hydrodynamical processes determined by the density difference between the river water and the receiving water body. The present study combines laboratory experiments and numerical modelling to investigate the mean flow and turbulent structures of a neutrally or negatively buoyant river plume entering a laterally unconfined water body. It was revealed that in the lateral direction, the neutrally buoyant river plume first converges and then spreads over the whole water column, whereas the negatively buoyant river plume converges near the water surface, and at the same time, spreads near the bottom boundary. Shear layers and shear-induced coherent structures develop on both sides of the river plume and are tilted by buoyancy in the negatively buoyant case. Shear-induced coherent structures contribute significantly to local mixing, whose Strouhal number decreases with increasing local Richardson number.
Year: 2025