A two-dimensional GPU-based model for multi-layer solute transport in shallow water flow with arbitrary mesh topology

Transport of solutes or suspended sediments in estuaries and river channels is an important parameter for environmental scientists and is typically analyzed within the water column. Three-dimensional models coupled with transport equations can be used to estimate salt or suspended sediment concentrations along estuarine channels; however, their complexity often encourages scientists to seek alternative models adapted to specific natural processes (e.g., global turbidity, salinity evolution in estuaries, pollutant transport). In some cases, less computationally efficient models are required to achieve higher parameter resolution, or vice versa. To balance computational efficiency with the ability to capture the vertical evolution of transported solutes or sediments, this study employs a GPU-based multi-layer model derived from the two-dimensional shallow water equations. Together with the depth averaged horizontal advective transport, vertical mixing is modeled via eddy viscosity terms and settling velocity. The model is tested and calibrated first using steady and unsteady solute transport in a synthetic channel and, in a second stage, through a laboratory experiment simulating the evolution of a solute released from a lateral cavity.