Dispersion of unsorted particle cloud in ambient cross flow

For land reclamation or dredging projects large amounts of sediment and mud are often disposed in the designated areas of coastal waters. As a pre-requisite to the assessment of the environmental impact due to these projects, the dynamics and dispersion of the particle cloud should be determined. The distinctive features of the present problem are that the dynamics will be affected by the negative buoyancy induced, the settling velocity of the sediment particles, and the cross-flow velocity. In this dissertation, the dispersion of unsorted particle cloud in ambient cross flow is studied by means of laboratory experiments and numerical models.;This dissertation includes 5 chapters. In the first chapter, a systemic review of previous works related to particle cloud and multiphase flows is made. In the second chapter, a series of laboratory experiments has been conducted to investigate the cross-flow and mixing of particle cloud in cross-flow with different particle sizes, initial volumes and ambient flow velocities. The continued motion process of the dumped sand in the flow has been recorded by a digital video camera. Then, the longitudinal width, and longitudinal and vertical frontal position of cloud have been measured using the imagine process software and the temporal variation of cloud size and frontal position of the particle cloud have then been obtained. The measurements suggest a roughly linear relationship between the displacement of the frontal position and the longitudinal width of the sand cloud. Three dimensionless empirical constants (alpha1, alpha2 and alpha3) of sand particle clouds in ambient cross-flow, which represent the relationship between the non-dimensional vertical frontal position Zfn of the particle cloud against non-dimensional time tn, the non-dimensional vertical frontal position Zfn against the non-dimensional longitudinal width Lfn of a particle cloud, and the non-dimensional longitudinal width Lfn of a particle cloud against non-dimensional time t n respectively, are obtained.;In the third chapter, a 3D numerical model using the k-epsilon parameterization of turbulence for the fluid phase and a Lagrangian method for the particle phase has been developed. In the fourth chapter, the numerical results are presented and compared with the measured results.;In the last chapter, the main conclusions are summarized and further work is suggested. (Abstract shortened by UMI.).