Effect of a cylinder on the transport of a solute released downstream of a step M. Abdollahpour P. Gualtieri C.Gualtieri

Rivers are vital for ecosystems as they provide habitats for aquatic life. The presence of step-like structures on river or lake bottoms is of interest in environmental studies due to the localized recirculation zones and transverse flows. Additionally, wooden logs as cylindrical obstacles lodged downstream of the step, further altering flow characteristics. This can result in the accumulation of solutes, such as contaminants and nutrients. Numerical simulations using OpenFOAM were conducted to investigate the impact of a cylinder downstream of a step on solute releasing from the bottom corner. Two-dimensional simulations were conducted at a Reynolds number based on step height (Reh) of 100 with a Schmidt number (Sc) of 500. Solute distribution in the fluid, Residence Time Distribution (RTD), and hydraulic efficiency indicators at different locations in the domain were comparatively studied. The study revealed that a cylindrical obstacle downstream of a step-like structure significantly influences the solute transport, causing it to be washed rapidly away from the recirculation zone.