Collaborative Research: Thermal Transport in Elastic Turbulence

合作研究：弹性湍流中的热传输

• 批准号: 1336085
• 负责人: Phillip Ligrani
• 金额: $ 19.94万
• 依托单位: Saint Louis University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-10-01 至 2014-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1336085&HistoricalAwards=false
• 关键词: Collaborative; Research; Thermal; Transport; Elastic

CBET 1336085PI: 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 1336085 PI：P. Ligrani（SLU）、R.聚合物添加剂，如聚丙烯酰胺，在液体中具有独特的特性，包括高度非线性，非牛顿行为。为了增强运输，聚合物通过流动应变在收缩中拉伸，这是由例如流线曲率引起的。聚合物的延展性和所产生的聚合物变形导致局部弹性应力的急剧增长，这是一系列被称为韦森伯格不稳定性的事件，当韦森伯格数大于约1/2或0.5时发生。总体结果包括聚合物粘度增加，在某些情况下，增加多达3个数量级。这种变化还导致有效聚合物热导率的增加和热传递的增强。然而，从弹性湍流的热传输的这种增加从来没有被调查过，因此，开发创新的方法，以提高混合和热传输在小规模的环境中在低雷诺数，实验和模拟将协调和弹性湍流的热传输进行。一个主要目的是确定使用弹性湍流来增强热传输的功效，通过实验和数值表征的现象。将使用三维直接数值模拟（DNS）对测量和非测量量的物理趋势进行数值建模和预测。因此，另一个总体目的是增强对与弹性湍流相关的物理过程的基本理解，因为它是由受到流动应变拉伸和收缩的聚合物在液体中引起的。由此产生的产品将是新的数值和分析模型，以描述和代表相关的弹性湍流物理现象，特别是热传输。通常，将采用毫米级（或毫米级）装置和流动环境来产生在D-Couette和Dean流动几何形状中的流动。这些流动各自提供剪切和流线曲率（离心效应），因此理想地适合于在稀聚合物溶液中产生弹性湍流。作为这项研究的一部分，一个新的普朗特数模型和一个新的有效电导率模型的弹性湍流也将开发。这将通过测量流动特性（时变和时均）和传热系数以及使用非线性弹性模型（如FENE-P）进行全三维直接数值模拟（DNS）来促进，以阐明聚合物溶液特性。本研究遵循几个重要的最近，相关的流体力学调查，因此，将解决重要的知识差距的影响和聚合物添加剂的热传输在毫尺度和微尺度的液体流动的影响。因此，本研究是高度转型和相关的，因为新的物理理解，这将提供，因为各种各样的应用。近年来，人们对与微型化有关的技术进步给予了很大关注，特别关注微米级和纳米级的技术，但也关注毫米级的器件。例如，制造技术和微制造的改进已经导致各种不同类型的设备和传感器的小型化。预测这些设备内部和周围的流体运动的能力对于它们的设计和优化至关重要。随着这些装置的长度尺度对于液体流动的减小，效果变得显著，这在较大规模的装置中不存在。由于所涉及的小尺寸和非常低的速度，在这些部件内的流动通常是层流，具有相对低的混合和热传输幅度。因此，这种层流是由微型装置的小尺寸所施加的限制的结果。这种流动以及与之相关的设备对于制药、医学、传热、生物医学工程和电子冷却等领域的一系列应用至关重要。在每种情况下，与这些应用领域相关的装置通常会受益于增加的混合和增强的弹性湍流传输。这种混合对于所提到的应用领域内的各种情况是重要的，包括使用液体来冷却电子部件、混合不同的化学成分以制造药物、涉及不同流体流的相互作用和混合的芯片实验室设备、以及用于从汽车到电器到空间系统（包括卫星）内的部件的设备中的微型热交换器。