Interaction of multiphase fluids and solids at the microscale

多相流在科学、工程和医学的各种过程中都很重要。在大多数实际情况下，多相流与可变形固体发生机械相互作用。流固相互作用在宏观尺度问题中得到了广泛的研究，其中表面张力的影响可以忽略不计。然而，由于人造物体的不断小型化和表面张力在自然现象中的重要性，迫切需要更好地理解表面张力起主导作用的流固相互作用。使用一种独特的计算方法，该项目将揭示流固耦合流动、非线性弹性和表面张力的基本机制。本研究将对软基质上的自发液滴运动过程、软毛细管中的界面不稳定性以及可变形固体表面上的池沸腾等问题进行研究。对这些现象的理解可能会在仿生液滴运动、微流体学和多相传热等方面取得重大进展。通过在本科机械工程课程中引入流体-结构相互作用的简单概念，该研究将整合到课程中。该项目还将为本科生提供暑期研究体验和指导活动。这个项目的目标是了解流体-固体相互作用，其中表面张力与流动、流体-流体相变和弹性力相互作用。这些现象在微流体、医学和自然现象中无处不在，由于我们缺乏理论和计算工具，以前没有研究过这些现象。这种知识差距限制了我们在多相传热、微流体、生物流体和微制造等科学和工程应用方面的进展。目前的项目将利用一种独特的计算方法来揭示控制这个迷人的耦合问题的基本机制。该项目将侧重于基础科学问题，涉及(i)软毛细管中流体被另一种流体取代，（ii）软基质上液滴的自发运动，以及（iii）可变形基质对温度驱动的液-气相变的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Multiphase flows are important in a wide variety of processes in science, engineering and medicine. In most cases of practical interest, multiphase flows interact mechanically with deformable solids. Fluid-solid interactions have been widely studied for macroscale problems, where the effect of surface tension is negligible. However, due to the continuous miniaturization of manufactured objects and the importance of surface tension in natural phenomena, there is a critical need to better understand fluid-solid interactions where surface tension plays a predominant role. Using a unique and enabling computational method, this project will unravel the fundamental mechanisms of fluid-solid interactions that couple flow, nonlinear elasticity and surface tension. The proposed research will shed light on the process of spontaneous droplet motion on soft substrates, interfacial instabilities in soft capillary tubes, and pool boiling on deformable solid surfaces. The understanding of these phenomena may bring major advances in bioinspired droplet motion, microfluidics and multiphase heat transfer. The research will be integrated in the curriculum through an initiative to introduce simple concepts of fluid-structure interaction in undergraduate mechanical engineering courses. The project will also offer undergraduate summer research experiences and mentoring activities. The goal of this project is to understand fluid-solid interactions where surface tension interacts with flow, fluid-fluid phase transformations and elastic forces. These phenomena, ubiquitous in microfluidics, medicine, and natural phenomena, have not been previously studied partially due to our lack of theoretical and computational tools. This knowledge gap is limiting our progress on multiphase heat transfer, microfluidics, biofluids and microfabrication, among other science and engineering applications. The current project will leverage a unique computational approach to unveil the fundamental mechanisms controlling this fascinating coupled problem. The project will focus on fundamental scientific problems involving (i) the displacement of a fluid by another fluid in a soft capillary tube, (ii) the spontaneous motion of droplets on soft substrates, and (iii) the effect of deformable substrates on temperature-driven liquid-vapor phase transformations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.