Elastic 'Ribbing' Instabilities in Fluid-Fluid Displacement Flows

摘要CTS-0089502B。华盛顿大学霍马米-这是华盛顿大学和斯坦福大学提交的两份相同的提案之一。提出了一种实验和数值相结合的研究方法，以考察弹性对流体-流体驱替界面稳定性的影响--有时被称为“肋状”不稳定性。这种不稳定性限制了工业过程中胶粘剂涂层的生产速度或质量。这是华盛顿大学的Bamin Khomami和斯坦福大学的Eric Shaqfeh合作进行的，数值部分主要在前者机构进行，而实验部分主要在后者机构进行。PI‘s进行的初步实验表明，这种不稳定的戏剧性开始。假设这种不稳定性是由位移锋附近的伸展指状流产生的不稳定应力梯度造成的。研究计划是利用现代仪器获得这种不稳定流动的定量实验数据，对流动进行线性和非线性稳定性分析，并对不稳定弹性流体界面进行全三维模拟，以验证假设。此外，还将通过模拟来检验通过引入时间周期参数强迫来增强系统稳定性的可能性。

AbstractCTS-0089502B. Khomami, Washington UniversityThis is one of two identical proposals submitted by Washington University and Stanford University. A combined experimental and numerical study is proposed to examine the effect of elasticity on the stability of fluid-fluid displacement interfaces-sometimes known as the "ribbing" instability. Such instabilities limit either the speed or the quality of production of adhesive coatings in industrial processes. This is a collaborative effort between Bamin Khomami of Washington University and Eric Shaqfeh of Stanford University with the numerical part being carried out mainly in the former institution while the experimental part mainly at the latter institution. Preliminary experiments performed by the PI's showed the dramatic onset of such instabilities. It is hypothesized that the instability is caused by the unstable stress gradient created by the extensional finger flow near the displacing front. The research plan is to obtain quantitative experimental data of such instability flows using modern instrumentation, to carry out linear and nonlinear stability analysis of the flows, and full three-dimensional simulations of the unstable elastic fluid interfaces to test the hypothesis. In addition, the possibility of enhancing the stability of the system by introducing time-periodic parametric forcing will be examined by simulations.