Collaborative Research: Experimental and numerical study on the Reynolds number dependence of surfaces in von Karman turbulent swirling flows

表面的生长被认为是无限薄的界面，将具有不同性质的流体所占据的区域分开，是一个具有内在和实际意义的过程，在自然、科学和技术设备中具有广泛的应用。由于不同的流体在分离它们的界面处混合和相互作用，表面的生长和破坏速率的定量表征是至关重要的。描述湍流中这些过程的综合理论是最常见的流动，目前还没有。该项目的最终目标是制定一个系统的理论，描述湍流中的表面动力学取决于流体的运动状态。表面动力学的综合理论将增强湍流的一般理论，包括在化学和能量转换系统中发现的具有混合和化学反应的流动。此外，该项目将提高对自然界中观察到的物理过程的理解，例如云的形成，其中界面的演变是速率限制过程。因此，虽然这项工作具有根本性，但它有可能对科学和技术产生广泛的影响。该项目将支持两名研究生的教育，还将包括重要的推广教育活动，重点是通过调查流体混合的性质，使4-7年级的学生参与科学发现。该项目的首要目标是量化湍流中表面演变对雷诺数的依赖性。我们结合联合收割机直接数值模拟和测量在一个新的冯卡门湍流旋流设置具有剪切驱动的封闭流之间的反向旋转叶轮充分发展的湍流在高雷诺数。在这个典型的实验室流的表面的演变进行定量跟踪，而描述的流配置的参数是明智地变化，以探测在参数空间中的不同的影响被认为是发挥作用的表面的演变的条件范围广泛。该项目将通过侧重于两个方面来实现这一广泛目标：㈠证明或反驳湍流中大表面面积和增长率对雷诺数的依赖性; ㈡通过详细分析湍流中表面的输运方程中的各项，确定缩放湍流中表面演变的参数。整个设备的直接数值模拟包括所有几何复杂性，而实验功能的一种新的方式产生的表面上的需求和国家的最先进的体积测量的速度场和三维表示的湍流。这一新颖独特的研究计划是前所未有的，因为它包括了湍流表面研究中所考虑的最宽范围和最高雷诺数。该奖项反映了NSF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。

The growth of surfaces, thought of as infinitely thin interfaces that separate regions occupied by fluids with different properties, is a process of intrinsic and practical interest with wide ranging applications in nature, science, and technical devices. As dissimilar fluids mix and interact at interface that separates them, the quantitative characterization of the rates of growth and destruction of surfaces is of critical importance. A comprehensive theory that describes these processes in turbulent flows, which are the most common flows encountered, is unavailable at present. The end goal of the project is to formulate a systematic theory that describes the dynamics of surfaces in turbulent flows depending on the state of the motion of the fluid. A comprehensive theory on the dynamics of surfaces will augment the general theory of turbulent flows, including flows with mixing and chemical reaction, which are found in chemical and energy conversion systems. In addition, this project will improve the understanding of physical processes observed in nature, such as cloud formation, where the evolution of interfaces is the rate limiting process. Thus, although the work is fundamental in nature, it has the potential for broad impacts in science and technology. The project will support the education of two graduate students, and it will also include significant outreach educational activities, which will focus on engaging grades 4-7 students in scientific discovery by investigating the properties of fluid mixing.The overarching goal of the project is to quantify the dependence of the evolution of surfaces in turbulent flows on the Reynolds number. We combine direct numerical simulations and measurements in a novel von Karman turbulent swirling flow setup featuring a shear-driven closed flow between counter-rotating impellers with fully developed turbulence at high Reynolds numbers. The evolution of surfaces in this canonical laboratory flow is tracked quantitatively, while the parameters that describe the flow configuration are varied judiciously to probe a broad range of conditions in the parameter space where different effects are believed to play a role on the evolution of surfaces. The project will fill this broad goal by focusing on two thrusts: (i) Prove or disprove the Reynolds number dependence of the area and growth rates of large surfaces in turbulent flows; (ii) Identify the parameters that scale the evolution of surfaces in turbulent flow through a detailed analysis of the terms in the transport equation for surfaces in turbulence. The direct numerical simulations of the entire device include all geometrical complexities, while experiments feature a novel manner of generating surfaces on demand and state-of the art volumetric measurements of the velocity field and 3D representation of the turbulent. This novel and unique research program is unprecedented as it includes both the broadest range and highest Reynolds numbers ever considered in the study of surfaces in turbulent flows.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.