Modeling stratified environmental flows

由于温度、盐度和/或沉积物浓度的变化，我们的内陆和沿海水域大多是密度分层的。这种密度分层禁止了热量、氧气、营养物质和污染物的垂直输送，从而对水系水质的理解和建模构成了巨大的挑战。这项研究的长期目标是寻求更好地了解密度分层水流的输送过程和混合机制，并开发计算机模型来预测和管理我们内陆和沿海水域的水质。这项研究的短期目标是：(1)更好地了解底坡分层流中的混合机制，并量化界面混合量；(2)研究一种经济的水库放流水质管理方法，以保护下游渔业；(3)建立气水分层流界面上的空气卷吸模型；以及研究几个与分层流有关的实际问题，包括利用气泡羽流和分层池塘中的沙射来进行分层。这项研究的主要不确定性是不同密度的流体之间的混合量。实验室实验将研究不同流动条件和层状结构下的混合。将使用一种名为粒子图像测速仪的技术测量流场，并将使用激光诱导荧光系统测量混合。实验结果将被用于开发工程使用的配方，并校准和验证计算流体力学模型，这些模型将用于优化我们的水上系统的管理。

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.