Thesis (M. Eng. in Ocean Engineering)--Joint Program in Marine Environmental Systems (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 1998. / Includes bibliographical references (leaves 70-71). / Optical imaging techniques can be used to provide a better understanding of the physical properties of particle clouds. The purpose of this thesis is to design, perform and evaluate a set of experiments using optical imaging techniques to characterize parameters such as shape factor and entrainment coefficient which govern the initial descent phase of particle clouds in water. Several different aspects of optical imaging are considered and evaluated such as the illumination, camera, and data acquisition components. A description of the experimental layout and procedure are presented along with a description of the image processing techniques used to analyze the data collected. Results are presented from a set of experiments conducted with particle sizes ranging from 250 to 980um. A shape factor is used to demonstrate how the cloud's shape changes from approximately spherical to approximately hemispherical over depth. The entrainment coefficient is shown to vary both as a function of depth and particle size diameter. The experimental cloud velocity is compared to the output of a simplified version of the model, STFATE, used to simulate the short term fate of dredged materials in water. This analysis provides a method of evaluating the experimental results and examining the feasibility of using the experimental data to refine the input parameters to the model. / by Elizabeth J. Bruce. / M.Eng.