Visualization of Fluid Flow in Wall's Near Field Using Evanescent Wave Mach-Zehnder Interferometer

使用倏逝波马赫-曾德干涉仪对壁近场中的流体流动进行可视化

• 批准号: 15560177
• 负责人: YAMADA Jun
• 金额: $ 2.3万
• 依托单位: University of Yamanashi
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560177/
• 关键词: Visualization; Evanescent Wave; Near Field; Shear Stress; Interferometer; Flow Structure

It is well known that heat and mass transfer between a wall and fluid flow, as well as drag by fluid flow strongly depend on the flow close to the surface of walls or objects. In order to improve the efficiency of fluid machine, enhance the heat transfer and/or control evaporation or condensation rate, it is very essential to know the detail of fluid flow close to the surface.To understand the detail of the fluid flow, a visualization technique for shear stress on wall surface, which is closely related to the fluid flow on the surface, has been proposed in this study. The visualization technique is based on the Mach-Zehnder Interferometer. Alight for observation is derived to a prism and induces evanescent wave on the prism surface during total internal reflection. After that, the light is interfered with the other light for reference. If the reflective index of fluid at the region of the evanescent wave changes due to shear stress by the surface, the phase of the observation light also changes and is observed as an interference pattern. In this study, the visualization system has been constructed and empirically examined to evaluate the validity of the technique. It was clarified that the phase shift is less to be observed when the evanescent wave is directly used for an observation light. We propose a new system for observing the shear stress. The new system introduces a thin film having a large optical elastic effect on the prism surface. The observation light goes through the thin film while the light is totally reflected by the thin film surface so that the optical pass gets longer. The new system constructed in the second year of this study enable us to visualized the shear stress on the surface when the stress is strong.

众所周知，壁面与流体流动之间的热质传递以及流体流动的阻力强烈地依赖于靠近壁面或物体表面的流动。为了提高流体机械的效率、强化传热和控制蒸发或冷凝速率，了解流体在壁面附近流动的细节是非常必要的，为了了解流体流动的细节，本文提出了一种与流体在壁面流动密切相关的壁面剪应力可视化技术。可视化技术是基于马赫-曾德尔干涉仪。观察用的光入射到棱镜上，在棱镜表面产生倏逝波。之后，该光与另一光干涉以供参考。如果在渐逝波区域处的流体的反射率由于表面的剪切应力而改变，则观察光的相位也改变并且被观察为干涉图案。在这项研究中，可视化系统已被构建和实证检验，以评估该技术的有效性。明确了当将倏逝波直接用于观察光时，观察到的相移较少。我们提出了一个新的系统来观察剪切应力。新系统在棱镜表面引入了一层具有较大光学弹性效应的薄膜。观察光穿过薄膜，同时光被薄膜表面全反射，使得光路变长。在本研究的第二年构建的新系统使我们能够可视化的表面上的剪切应力时，应力是强大的。