U.S.-Austria Cooperative Research on the Hydrodynamic Stability of a Resuspended Layer

该奖项支持纽约城市学院的Andreas Acrivos教授与维也纳技术大学流体动力学和传热研究所的Uwe Schaflinger教授合作研究重悬浮层的流体动力学稳定性。crivos博士的几名研究生和博士后将参与该项目。最近已经确定，在层流条件下，最初沉降的固体颗粒床由于剪切作用而重新悬浮。进一步的实验表明，由于界面波的作用，重悬浮层与透明流体之间的界面变得不稳定。拟议的合作研究的目的是将数值计算与精心指导的实验相结合，以验证从空间不稳定流过渡到绝对不稳定流的理论预测，并深入了解波浪产生和破裂的机制。​这项研究将使用Schaflinger博士设计和建造的实验装置来研究二维通道中的基本再悬浮流动。他和他在维也纳的团队在流体动力学，特别是两相流的实验技术，分析和数值方法方面非常有经验。与此相辅相成的是CCNY在剪切诱导颗粒迁移，流体动力稳定性和流变学领域的国际公认的专业知识。他们正在进行的粘性再悬浮理论研究将通过这次实验合作大大加强。再悬浮在大多数泥沙输运现象中起着重要作用，包括工业问题，如横流微滤。负浮力粒子沉降层重悬浮的条件尚不清楚，通常与高雷诺数下的湍流有关。再悬浮也可以发生在低雷诺数，惯性效应不显著，流动是层流。该项目将根据CCNY正在进行的分析和数值研究，通过调整流动参数，对两种叠加层状流体界面的不稳定性进行系统研究。它将导致对粘性重悬浮和多相流稳定性的基本见解。

This award supports Professor Andreas Acrivos of the City College of New York to collaborate with Professor Uwe Schaflinger of the Institute of Fluid Dynamics and Heat Transfer, Technical University of Vienna, in a study of the hydrodynamic stability of a resuspended layer. Several graduate students and postdoctoral associates of Dr. Acrivos will participate in the project. It has recently been established that under laminar conditions an initially settled bed of solid particles is resuspended due to action of shear. Further experiments have shown that the interface between the resuspended layer and the clear fluid becomes unstable due to interfacial waves. The aim of the proposed cooperative research is to combine numerical calculations with carefully directed experiments in order to verify the theoretical prediction of a transition from a spatially to an absolutely unstable flow and to gain insight into the mechanisms responsible for the creation and the breakup of the waves. The research will use an experimental setup designed and built by Dr. Schaflinger to study the basic resuspension flow in a two dimensional channel. He and his group in Vienna are very experienced with experimental techniques, analytical and numerical methods in fluid dynamics and specifically in two phase flows. Complementing this is the internationally recognized expertise of the group at CCNY in the fields of shear induced migration of particles, hydrodynamic stability and rheology. Their ongoing theoretical investigation of viscous resuspension will be greatly enhanced by this experimental collaboration. Resuspension plays an important role in most sediment transport phenomena, including industrial problems such as cross flow microfiltration. The conditions under which a settled layer of negatively buoyant particles will resuspend are not well understood and are usually associated with turbulence at high Reynolds numbers. Resuspension can also occur at low Reynolds numbers for which inertial effects are insignificant and the flow is laminar. This project will produce a systematic study of the instabilities at the interface of two superposed stratified fluids by adjusting the parameters of the flow in accordance with the ongoing analytical and numerical investigations at CCNY. It should result in fundamental insights into viscous resuspension and the stability of multiphase flows.