Modelling of hydrodynamics and solid transport in a large stormwater detention and settling basin

Settling processes of particles in stormwater detention basins are still not well known and modelled. Difficulties exist to transpose the results obtained on laboratory scale physical models to real basins in sewer systems because of complex geometry, unsteady hydrodynamics, variable fluxes and particles characteristics, etc. In order to contribute to improve the design and the management of large stormwater detention and settling basins, experimental and modelling investigations have been carried out in the Django Reinhardt stormwater detention and settling basin in Chassieu (Lyon, France). The calibrated Rubar20 2D CFD software based on convection-diffusion terms coupled to the Barré de Saint Venant equations enables to reproduce the hydrodynamics with errors less than 15 % and shows good capacity to estimate the sedimentation distribution on the bottom of the basin. 3D simulations with Fluent CFD software highlight good correlations between skin friction coefficient, Reynolds stress according to x-direction, results obtained with Rubar20 on sedimentation distribution and the real observed sedimentation zones.