Analysis of Convection in the Presence of Apparent Slip

hodes， Tufts大学工程结构表面在过去十年中出现，具有类似于自然发生的结构表面（如荷叶）的特性。例如，它们提供润滑，使液滴从它们身上滚下来，而不是粘在它们身上，因此具有“自清洁”功能。应用包括减少阻力和操作液滴实验室芯片设备上的化学和生物分析。该研究将为利用结构表面的润滑特性为未来几代微电子器件的液态金属冷却奠定理论基础。事实上，液态金属冷却的挑战是减少液态金属流过半导体材料的阻力，这可以通过利用结构表面来实现。最终结果是，用于计算的微电子电路和用于雷达和通信的射频单片微波集成电路（RF mmic）上的投射热负荷可以被容纳。PI将与纳肖巴地区高中的一名教师和ARL设计公司的一名科学家合作，为高中生开发和试点一个动手模块，以学习结构表面。在绝热系统的情况下，根据过去十年积累的大量文献，液体在结构表面上的层流已经相当好地理解了。然而，对非绝热的层流在结构表面上的研究缺乏，即那些与液体有热量传递或从液体流出的表面。值得注意的是，以往所有关于非绝热流动的研究都忽略了三个实质性的影响，即由于传热和半月板曲率的影响，热毛细应力和沿半月板的蒸发和凝结。该研究将使用保角映射和卷积理论来开发表观流体动力滑移长度和表观热滑移长度的解析表达式，以描述在存在每种效应的情况下流动与平行脊、横向脊和柱几何结构的局部相互作用。然后，（平均）流向动量和热能方程的解将用于计算两个关键的工程参数，摩擦系数和努塞尔数。在可能的范围内，研究将以分析的方式捕捉所有3种耦合效应。必要时，将采用数值方法同时捕获所有3种耦合效应。最后，提出的工作将考虑紊流非绝热流动。紊流之所以令人感兴趣，是因为表观滑移长度的长度尺度通常与粘性亚层的长度尺度相当，因此表观滑移效应并不局限于微通道。

CBET-1402782Hodes, Tufts UniversityEngineered structured surfaces have emerged during the past decade and possess properties similar to those of naturally occurring structured surfaces such as the lotus leaf. For example, they provide lubrication such that droplets roll off of them rather than adhere to them and are thus "self-cleaning". Applications include drag reduction and manipulation of droplets on lab-on-a-chip devices for chemical and biological assays. The proposed research would lay the theoretical foundation to exploit the lubricating properties of structured surfaces to enable liquid metal cooling of future generations of microelectronic devices. Indeed, the challenge with liquid metal cooling is reducing the resistance to the flow of liquid metal through a semiconducting material and this can be accomplished by utilizing structured surfaces. The end result is that projected heat loads on microelectronic circuits used for computing and radio frequency monolithic microwave integrated circuits (RF MMICs) used for radar and communications may be accommodated. The PI will collaborate with a teacher at Nashoba Regional High School and a scientist of ARL Designs to develop and pilot a hands-on module for high school students to learn about structured surfaces.In the case of an adiabatic system, laminar flows of liquid over structured surfaces are fairly well understood as per a body of literature amassed during the past decade. However, there is a dearth of studies on diabatic, laminar flows over structured surfaces, i.e., those where there is heat transfer to or from the liquid. Significantly, all previous studies on diabatic flows neglect 3 substantial effects, i.e., thermocapillary stress and evaporation and condensation along menisci on account of heat transfer, and curvature of menisci. The research will use conformal mapping and convolution theory to develop analytical expressions for the apparent hydrodynamic slip length and apparent thermal slip length necessary to describe the local interaction of the flow with the structures of the parallel ridge, transverse ridge and pillar geometries in the presence of each effect. Then, solution of the (mean) streamwise-momentum and thermal energy equations will be used to compute the two key engineering parameters of interest, friction factor and Nusselt number. To the extent possible, the research will capture all 3 coupled effects analytically. If necessary, numerical methods will be utilized to capture all 3 coupled effects simultaneously. Lastly, the proposed work will consider turbulent diabatic flows. Turbulent flows are of interest because the length scale of the apparent slip lengths is typically on par with that of the viscous sublayer such that apparent slip effects are not limited to microchannels.