Collaborative Research: Thermal Transport in Elastic Turbulence

合作研究：弹性湍流中的热传输

• 批准号: 1652090
• 负责人: Robert Handler
• 金额: $ 4.25万
• 依托单位: George Mason University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2017-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1652090&HistoricalAwards=false
• 关键词: Collaborative; Research; Thermal; Transport; Elastic

CBET 1335748PI: P. Ligrani (SLU) /R. Handler (TAMU)Polymer additives, such as polyacrylamide, have unique characteristics in liquids, including highly non-linear, non-Newtonian behavior. To augment transport, the polymers are stretched in constriction by flow strain, which is induced by, for example, streamline curvature. The extensibility of the polymer and resulting polymer deformation, leads to a sharp growth in the local elastic stress, a sequence of events referred to as the Weissenberg instability, which occurs when the Weissenberg number is greater than approximately ½ or 0.5. Overall consequences include increased polymer viscosity, in some cases, by up to 3 orders of magnitude. Such changes also lead to increases in effective polymer thermal conductivity, and augmentation of thermal transport. However, such increases in thermal transport from elastic turbulence have never before been investigated, and thus, to develop innovative methods to enhance mixing and thermal transport in small-scale environments at low Reynolds numbers, experiments and simulations will be coordinated and conducted on thermal transport in elastic turbulence. One principal aim is to determine the efficacy of using elastic turbulence to augment thermal transport, by characterizing the phenomena both experimentally and numerically. Numerical modeling and prediction of the physical trends of both measured and non-measured quantities will be performed with three-dimensional Direct Numerical Simulations (DNS). As such, another overall intent is enhancement of fundamental understanding of the associated physical processes associated with elastic turbulence, as it is induced in liquids by polymers subject to stretching and constriction by flow strain. A resulting product will be new numerical and analytic models to describe and represent the related elastic turbulence physical phenomena, especially thermal transport. Generally, milliscale (or millimeter-scale) devices and flow environments will be employed to produce flows in the rotating-Couette and Dean flow geometries. These flows each provide shear and streamline curvature (centrifugal effects) and thus are ideally suited to producing elastic turbulence in dilute polymer solutions. As part of this research, a new Prandtl number model and a new effective conductivity model for elastic turbulence will also be developed. This will be facilitated by measurements of flow characteristics (time-varying and time-averaged) and heat transfer coefficients, and fully three-dimensional direct numerical simulations (DNS) with non-linear elastic models, such the FENE-P, to elucidate polymer solution characteristics. The present study follows several important recent, related fluid mechanics investigations, and as such, will address important gaps in knowledge regarding the effects and influences of polymer additives on thermal transport in milliscale and microscale liquid flows. As such, the present study is highly transformational and relevant because of the new physical understanding which will be provided, and because of the variety of applications. In recent years, much attention has been devoted to technological advances related to miniaturization, with particular attention to technologies at the micro-scale and nano-scale, but also to milli-scale devices. For example, improvements in manufacturing technology and micro-fabrication have led to the miniaturization of a variety of different types of devices and sensors. The ability to predict the fluid motion in and around these devices is essential for their design and optimization. As the length scales of these devices decrease for liquid flows, effects become significant which are not present in larger-scale devices. Because of the small dimensions and very low speeds which are involved, the flows within these components are generally laminar, with relatively low magnitudes of mixing and thermal transport. Such laminar flows are thus a consequence of the limitations imposed by the small sizes of the miniature devices. Such flows, and the devices associated with them, are vital and important for a range of applications in areas such as pharmaceutics, medicine, heat transfer, biomedical engineering, and electronics cooling. In every case, the devices associated with these application areas would generally benefit by increased mixing and augmented transport from elastic turbulence. Such mixing is important for a variety of situations within the mentioned application areas, including the use of liquids to cool electronic components, mixing of different chemical components to manufacture pharmaceuticals, lab-on-a-chip devices which involve the interaction and mixing of different fluid streams, and miniature heat exchangers for use in devices ranging from automobiles, to appliances, to components within space systems, including satellites.

CBET 1335748PI：P。Ligrani（Slu） /r。处理剂（TAMU）聚合物添加剂（例如聚丙烯酰胺）在液体中具有独特的特征，包括高度非线性的非牛顿行为。为了增强运输，聚合物通过流量应变延伸，这是由流线曲率诱导的。聚合物和产生的聚合物变形的可扩展性导致局部弹性应激的急剧生长，这是一系列事件，称为魏森堡不稳定性，当魏森伯格数量大于大约½或0.5时发生。总体后果包括在某些情况下提高聚合物粘度，最多3个数量级。这种变化还会导致有效聚合物热导率和热传输的增加。然而，从弹性湍流中的热传输增加从未在研究之前进行研究，因此，在较低的雷诺数字下，在小规模环境中增强混合和热运输的创新方法，实验和模拟将在弹性湍流中的热运输中进行协调并进行。一个主要目的是通过在实验和数值上表征使用弹性湍流来增强热运输的有效性。将使用三维直接数值模拟（DNS）进行测量和未测量量的物理趋势的数值建模和预测。因此，另一个总体意图是增强对与弹性湍流相关的物理过程的基本理解，因为它是通过流量应变拉伸和收缩的聚合物在液体中诱导的。最终的产品将是新的数值和分析模型，以描述和表示相关的弹性湍流物理现象，尤其是热传输。通常，将采用Milliscale（或毫米级）设备和流动环境来产生旋转和院长流量几何形状的流动。这些流量各有剪切和流线曲率（离心效应），因此非常适合在稀聚合物溶液中产生弹性湍流。作为这项研究的一部分，还将开发一个新的PRANDTL数量模型和新的弹性湍流电导率模型。这将通过测量流动特性（时变和时间平均）和传热系数以及具有非线性弹性模型（例如Fene-P）的完全三维直接数值模拟（DNS）来制备。本研究遵循了几项最近的重要的，相关的流体力学研究，因此将解决有关聚合物添加剂对Milliscale和Microscale液体热传输的影响和影响的重要差距。因此，由于将提供新的物理理解，并且由于应用的多样性，因此本研究具有高度变革性和相关性。近年来，已经非常关注与小型化有关的技术进步，并特别关注微型和纳米级的技术，也关注Milli级设备。例如，改进制造技术和微型制作已导致各种不同类型的设备和传感器的微型化。预测这些设备内外的流体运动的能力对于它们的设计和优化至关重要。随着这些设备的长度尺度减小液体流量，效果变得显着，在大型设备中不存在。由于尺寸较小和涉及的非常低的速度，这些组件中的流量通常是层流，混合和热传输的幅度相对较低。因此，这种层流流是微型设备的小尺寸施加的局限性的结果。这种流以及与之相关的设备对于在药品，药物，传热，生物医学工程和电子冷却等领域的一系列应用中至关重要而重要。在每种情况下，与这些应用领域相关的设备通常都会通过增加弹性湍流中的混合和增强运输来受益。这种混合对于上述应用领域内的各种情况很重要，包括使用液体冷却电子组件，将不同的化学成分混合以制造药品，实验室芯片设备，涉及涉及不同流体流的相互作用和混合不同的流体流，以及在设备中用于自动型系统的空间，以供弹药机构成。