Modeling stratified environmental flows

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Most of our inland and coastal waters are density stratified as a result of variations in temperature, salinity and/or sediment concentration.  This density stratification prohibits the vertical transport of heat, oxygen, nutrients and pollutants, thus poses a great challenge to the understanding and modeling of water quality of aquatic systems.  The long-term objective of this study is to seek a better understanding of the transport processes and mixing mechanisms of density-stratified flows, and to develop computer models for prediction and management of the quality of our inland and coastal waters. The short-term objectives of this study are (1) to seek a better understanding of the mixing mechanisms in stratified flows over a bottom slope and to quantify the amount of the interfacial mixing, (2) to study an economical way of managing the water quality of reservoir release for protecting downstream fishery, (3) to model air entrainment at the interface of air-water stratified flows, and to study a few practically important problems related to stratified flows, including de-stratification using bubble plumes and sand jet in stratified ponds. The major uncertainty in this study is the amount of the mixing between the fluids of different densities.  Laboratory experimentation will be conducted to study the mixing under various flow conditions and stratifications.  Flow fields will be measured using a technique called particle-image-velocimetry and mixing will be measured using a laser-induced-fluorescence system. Experimental results will be used to develop formulations for engineering use, and to calibrate and validate computational fluid dynamics models which will be used to optimize the management of our aquatic systems.