Numerical modelling of 3D stratified free surface flows: a case study of sediment dumping

Abstract

SUMMARYA three-dimensional numerical model has been developed to simulate stratiÿed ows with free surfaces. The model is based on the Reynolds-averaged Navier-Stokes (RANS) equations with variable uid density. The equations are solved in a transformed -coordinate system with the use of operatorsplitting method (Int. J. Numer. Meth. Fluids 2002; 38:1045 -1068). The numerical model is validated against the one-dimensional di usion problem and the two-dimensional density-gradient ow. Excellent agreements are obtained between numerical results and analytical solutions. The model is then used to study transport phenomena of dumped sediments into a water body, which has been modelled as a strongly stratiÿed ow. For the two-dimensional problem, the numerical results compare well with experimental data in terms of mean particle falling velocity and spreading rate of the sediment cloud for both coarse and medium-size sediments. The model is also employed to study the dumping of sediments in a three-dimensional environment with the presence of free surface. It is found that during the descending process an annulus-like cloud is formed for ÿne sediments whereas a plate-like cloud for medium-size sediments. The model is proven to be a good tool to simulate strongly stratiÿed free surface ows.

An experimental study of mounds formed by dumping coarse sediment in channel flow

“…Ruggaber (2000) studied the settling behaviour of particle clouds in connection with disposal of dredged materials. Gu and Li (2004), Lin and Wang (2006) and Mondal and Mazumder (2006) reported numerical modelling of particle dispersion and dumping. None of these, however, included the deposition pattern due to coarse sand disposal.…”