A three-phase flow simulation of local scour caused by a submerged wall jet with a water-air interface

•A new three-phase model for sediment transport problems with a water-air interface.•A special modification to the interface-compression VOF method.•A verified three-phase model for local scour caused by submerged wall jets. Interactions between fluid and hydraulic structures and the resulting bed scouring are complex phenomena that involve three phases: water, air and sediment. This study presents a new rheology-based three-phase flow model that can (i) track the water-air interface in the presence of suspended sediment and (ii) predict the local scour caused by submerged wall jet. A modified volume-of-fluid (VOF) method was used to track the water-air interface, and a modified k-ϵ turbulence model was employed to capture important features of the turbulent flow, including turbulence modulation due to fluid-sediment interaction. The three-phase model was first used to study the sediment transport in open-channel flows in order to evaluate the performance of two models for particle response time, and then employed to simulate the scouring process downstream a submerged wall jet issued from a sluice gate. The simulated bed profiles showed good agreement with the measured. It was demonstrated that the three-phase model could capture important dynamic features such as sediment avalanche.