Collaborative Research: Double-diffusive sedimentation

CBET 1438052/1437275本项目将使用理论、数值模拟和实验来研究分层液体系统中由不稳定性引起的运动。例如，当淡水从河流进入海洋时，沉积物和盐的浓度梯度同时形成。在理论上可以预测的某些条件下，这些梯度的存在会导致不稳定的情况，从而引起含有沉积物的水的对流运动。初步结果表明，这种运动强烈地影响着泥沙的沉速和输移。本计画将发展一个分析框架，以分析在河口各种情形下，由这种不稳定性所引起的运动。然而，该框架将更广泛地适用于环境问题，地球物理，天体物理和工程flow.This合作项目将使用理论，计算和实验工具，探索在广泛的条件下的双扩散沉积的线性和非线性动力学。线性稳定性理论，直接数值模拟，和实验室实验将进行四个基本配置：a）一个层的含沙淡水盐水之上; B）一个层的含沙淡水盐水之下; c）线性浓度梯度与沉积物不稳定分层; d）线性浓度梯度与沉积物稳定分层。将包括适用于河口的水中剪切流的影响。这项研究将解决一系列有趣的现象，在这些系统中观察到的，包括指状不稳定性，水平侵入，和楼梯形成的颗粒系统。拟议的研究将确定主导的不稳定机制，在各种参数制度，并将提供定量的双扩散沉积在每种情况下的比例律。

CBET 1438052/1437275This project will use theory, numerical simulation, and experiments to study the motion that is induced by instabilities in stratified liquid systems. For example, when fresh water from a river enters the ocean, concentration gradients of sediment and salt form simultaneously. Under certain conditions that can be predicted theoretically, the presence of these gradients leads to an unstable situation that induces convective motion of the sediment-laden water. Preliminary results show that this motion strongly affects the settling velocity and transport of the sediment. This project will develop a framework for analyzing motions induced by such instabilities in a variety of situations pertaining to river estuaries. However, the framework will be more broadly applicable to problems in environmental, geophysical, astrophysical, and engineering flows.This collaborative project will use theoretical, computational, and experimental tools to explore the linear and nonlinear dynamics of double diffusive sedimentation under a wide range of conditions. Linear stability theory, direct numerical simulation, and laboratory experiments will be conducted for four basic configurations: a) a layer of sediment-laden fresh water above saline water; b) a layer of sediment-laden fresh water below saline water; c) linear concentration gradients with sediment being unstably stratified; d) linear concentration gradients with sediment being stably stratified. Effects of shear flow in the water, which is appropriate for river estuaries, will be included. The research will address a range of interesting phenomena observed in these systems including fingering instabilities, horizontal intrusions, and staircases formed in particulate systems. The proposed research will identify dominant instability mechanisms in various parameter regimes, and will provide quantitative scaling laws for double diffusive sedimentation in each case.