Research Initiation Awards: Study of Thermal Phenomena at Interfaces

固体表面的粗糙度测量，如薄膜和加工金属，在微尺度和纳米尺度表明，表面是粗糙和无序的几十年的长度尺度。在紊流界面中也观察到类似的特征。这种无序结构强烈影响界面的热现象。以前对这种界面的热现象的研究通常要么过于简化界面平滑的理想化，要么诉诸经验和半经验的分析方法。缺乏对这种现象的物理理解主要是由于无法量化这些结构中的紊乱。本研究提出使用分形几何的新概念来理解和表征无序表面的基本性质。这种表征在一定范围内量化了每个长度尺度上表面的结构。这对于在相关长度尺度上提供热现象与界面相互作用的关键见解尤为重要。将分形应用于接触电导的初步研究已经解释了一些先前的实验结果。基于这些令人鼓舞的前景，本研究提出使用分形来研究具有科学和工程重要性的界面热现象，如接触电导、摩擦加热和辐射与表面的相互作用。

Roughness measurements of solid surfaces, such as thin films and machined metals, at microscales and nanoscales show that the surfaces are rough and disordered over several decades of length scales. Similar features have been observed in turbulent fluid interfaces. Such disordered structures strongly influence thermal phenomena at interfaces. Previous studies on thermal phenomena at such interfaces have conventionally made either oversimplifying idealizations of smoothness of an interface or resorted to empirical and semi- empirical methods of analysis. This lack of physical understanding of the phenomena was mainly due to an inability to quantify the disorder in these structures. This study proposes to use the novel concepts of fractal geometry to understand and characterize the fundamental nature of disordered surfaces. Such a characterization quantifies the structure of surfaces at every length scale within certain limits. This is particularly important in providing key insight into the interactions of thermal phenomena with interfaces at relevant length scales. Preliminary studies on applying fractals in contact conductance have explained several previous experimental results. Based on these encouraging prospects, this study proposes to use fractals to study interfacial thermal phenomena of scientific and engineering importance such as contact conductance, frictional heating, and interactions of radiation with surfaces.