Numerical modelling of local scour caused by submerged jets

The local scour downstream of an apron caused by submerged jets issuing from a sluice gate is investigated by means of Flow-3D computational fluid dynamics code. The performance of the numerical model based on renormalisation group k-epsilon turbulence scheme and large-eddy simulation (LES) technique is evaluated by comparison with laboratory experiments. Various empirical formulas are coupled with the Flow-3D model to accurately simulate the bedload transport rate. The simulated evolution profiles of local scour are also compared with laboratory experiments. The simulation results show considerable numerical discrepancies between the renormalisation group k-epsilon and the LES closure scheme. The Flow-3D model by the LES closure scheme coupled with an appropriate bedload transport formula successfully captures the bed deformation. The simulation results provide a good quantitative means of predicting the formation of both the local scour and the sand dune caused by submerged jets. The present work highlights the potential of the numerical simulation technique and the empirical bedload formulas for the investigation of local scour.