Author(s): S. N. Chan
Linked Author(s): Shu Ning Chan
Keywords: Sediment transport; Buoyant jets; Particle tracking; Stochastic model
Abstract: Sediment-laden turbulent buoyant jets are commonly found in natural and engineered environments. A three-dimensional (3D) stochastic particle tracking model is developed to predict the particle fall out and deposition from sediment-laden buoyant jets in a stagnant ambient. The model is unique in its simple and robust way of simulating the complex 3D buoyant jet flow field and the modelling of turbulent velocity fluctuations. The model incorporates the three flow regimes involved in a buoyant jet, namely turbulent jet flow, jet entrainment-induced external flow and surface spreading current. The jet mean flow velocity is determined using a well-validated jet integral model. The external jet-induced irrotational flow field is computed by a distribution of point sinks along the jet trajectory. The surface spreading current is predicted using an integral model accounting for the interfacial shear. Turbulent velocity fluctuations are modelled by a velocity autocorrelation function which mimics the trapping of sediment particles in turbulent eddies. The parameters of the autocorrelation function include root-mean-square (RMS) turbulence velocity and turbulent time scale, which are estimated from best-fitted self-similar profiles of RMS turbulence velocity and turbulent energy dissipation rate derived from an independent computational fluid dynamics (CFD) solution of jets and plumes. For the first time, the bottom deposition of sediment-laden buoyant jets is successfully predicted using the 3D particle tracking model; model prediction shows excellent agreement with previous experimental data.
Year: 2013