Gravity-driven flows in stratified fluids

CBET-0756396 Linden当分层流体中具有不同垂直分层的两个区域接触时，与水平密度差异相关的浮力会导致两个区域的流体混合。这种混合过程是通过一种流体侵入另一种流体而发生的--一种流体沿着另一种流体的等密度面运动。流体可以在侵入体内平流输送很长距离，对物质、示踪剂、营养物、污染物和生物材料的运输以及两种流体的最终混合具有重要影响。的传播速度和入侵的分层的属性的大小的依赖性在很大程度上是未知的。这个建议的目标是确定这些关系，以确定入侵和内波之间的相互作用，并获得更深入的了解分层流体的动力学。即使是最简单的情况下，入侵传播沿着两个良好的混合层之间的界面没有得到很好的理解，尽管理论和实验工作延伸到过去25年。最近，PI在这个问题上取得了重大进展，并表明界面的上游偏转是这种流动的一个关键特征。这一结果提出了获得新的见解，更一般的情况下，一个连续分层的环境流体，这是能够支持波模式的频谱的可能性。计划对分层流体中重力驱动侵入体的动力学进行密切结合的实验、理论和计算研究。该项目旨在探索这些问题，目标是开发一个综合理论，将入侵耦合到它产生的内部波场。智力优点：作为一项直接的科学贡献，计划中的工作将确定和量化分层流体中侵入时空演变的主导机制。具体而言，研究将解决这样的问题，如传播的速度和它的入侵和环境分层的属性的依赖，界面和内部波的入侵和入侵的动力学的后续影响的产生。实验室实验和数值计算将被用来发展的动力学的理解和指导理论的发展，这将使结果被转化为分层流的更深入的理解。更广泛的影响：预测侵入体的速度和其他物理性质的能力对各种地球物理和环境流具有重要意义。在更基本的层面上，这个项目解决了重力场中不同流体如何混合的问题。PI希望这项研究的结果能为这个问题提供新的见解。它还将提供一个例子，结合使用数值，实验和理论技术对一个复杂的流体动力学问题，导致所有这些技术的改进。在教育方面，计划中的调查将允许研究生和本科生的培训，并进一步发展外国合作，先进的实验技术，理论建模和数值模拟的概念和方法。

CBET-0756396LindenWhen two regions within a stratified fluid with different vertical stratifications come into contact, buoyancy forces associated with the horizontal density differences cause the fluids from the two regions to intermingle. This intermingling process occurs through the intrusion of one fluid into the another - the motion of one fluid along isopycnal surfaces of the other. Fluid can be advected large distances within an intrusion, with important consequences for the transport of mass, tracers, nutrients, pollutants and biological material, and the ultimate mixing of the two fluids. The dependence of the propagation speed and the size of the intrusion on the properties of the stratification is largely unknown. The goal of this proposal is to determine these relationships, to determine the interactions between intrusions and internal waves, and to obtain a deeper understanding of the dynamics of stratified fluids. Even the simplest case of an intrusion propagating along an interface between two well mixed layers is not well understood, despite theoretical and experimental work extending back over the past 25 years. Recently, the PI has made significant progress on this problem and shown that upstream deflection of the interface is a key feature of this flow. This result raises the possibility of gaining new insights into the more general case of a continuously stratified ambient fluid which is capable of supporting a spectrum of wave modes. It is planned to conduct a closely integrated experimental, theoretical and computational investigation into the dynamics of gravity-driven intrusions in stratified fluids. This project is aimed at exploring these issues with the goal of developing a comprehensive theory that couples the intrusion to the internal wave field that it generates. Intellectual merit: As an immediate scientific contribution, the planned work will identify and quantify the mechanisms that dominate the spatio-temporal evolution of intrusions in a stratified fluid. Specifically, the research will address such issues as the speed of propagation and its dependence on the properties of the intrusion and the ambient stratification, the generation of interfacial and internal waves by the intrusion and their subsequent effect on the dynamics of the intrusion. Laboratory experiments and numerical calculations will be used to develop an understanding of the dynamics and guide a theoretical development that will enable the results to be translated into a deeper understanding of stratified flows. Broader impact: The ability to predict the speed and other physical properties of intrusions is of importance to a variety of geophysical and environmental flows. On a more fundamental level this project addresses the question of how different fluids in a gravitational field intermingle. The PIs expect the results of this study to provide new insights on this question. It will also provide an example of the combined use of numerical, experimental and theoretical techniques on a complex fluid dynamical problem, leading to refinements in all these techniques. On the educational side, the planned investigation will allow for the training of graduate and undergraduate students, and the further development of foreign collaboration, in the concepts and methods of advanced experimental techniques, theoretical modeling, and numerical simulations.