Our goal is to better understand near source sediment transport and eventually propose more effective land reclamation strategies and policies in support of Singapore’s continued physical growth, which now includes 25% reclaimed land. As a starting point, we have been systematically exploring the fluid mechanics of particle clouds and starting plumes that are formed when sediment is released into marine waters. We have conducted a number of experimental studies exploring the effects of ambient conditions (e.g., currents and waves), and release conditions (e.g., sediment type, volume, and height of release) on cloud coherency, trajectory, spreading and sediment loss. Our new experimental tank will allow testing of additional ambient conditions (turbulence and density stratification) as well as different release scenarios. (We are now simulating sediment released from a split-hull barge.) In addition to measurements collected with two-dimensional Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF), we will be collaborating with George Barbastathis’s team to image our clouds using 3-D holography, which should provided a more synoptic picture of our cloud. Theoretically, we have developed improved integral and numerical models to describe sediment and fluid transport within a cloud, and the flux of sediment across the cloud boundary as it enters the swarm (dispersive) phase. And we are using a Large Eddy Simulation model for more detailed simulations involving fluid-particle interactions. Finally, we are interested in integrating our “near field” physical and mathematical model results into far field transport models. We will be working with Paolo Rizzoli’s team on inputting our model output (e.g., vertical turbidity profiles) into FVCOM as an “inner” boundary (or source) condition.
Setup of the two-phase sediment cloud experiments
Effect of sediment particle size on cloud coherency (left: d=0.51mm; right: d=0.07mm)
Experimental observation of the two phase characteristics of a sediment cloud (Yellow: entrained fluid. Green: sediment particles)
Comparison of model predictions and experimental observations (Top: predictions; bottom: observations)
Large eddy simulation of (i) left: a dense starting jet, (ii) center: a neutrally buoyant jet, (iii) right: a positively buoyant jet