Development of 3D Micro-PIV techniques Applicable to Marangoni flows in small space

本研究的主要目的是：1）发展微尺度流场三维瞬时速度分布的测量技术; 2）利用现有的测量技术，研究表面张力与微尺度流场的相互作用。第一种方法是使用一对远心透镜的立体成像方法，其使得能够进行平行投影立体匹配。第二种方法利用数字同轴全息技术。本研究所发展之立体同轴全息术，系由一简单之光学装置及一简易之校正方法所组成。它沿光轴方向沿着提高了空间分辨率。第三种方法是使用彩色偏心孔径的散焦方法，它可以处理比普通散焦方法更高的示踪粒子分布密度。为了避免这些问题，一些单相机立体成像方法被开发出来。单摄像机立体方法对外界振动具有很强的鲁棒性，测量对象的尺寸假设为几十到几百微米。在如此小的空间中的流动受到表面张力的强烈影响。本研究的主要兴趣是表面张力和微通道中的Marangoni流的影响。由于测量技术的发展需要很长时间，因此尚未进行有关该问题的实验。为了进一步研究表面张力对微尺度流动的影响，在光学方法的基础上，本文在SPRING-8同步辐射装置上对三维PIV技术进行了可行性研究。

The purpose of this research has been as follows ;1) Development of the measurement techniques that enable to measure instantaneous three-dimensional velocity distributions in micro-size flow fields.2) By utilizing the developed techniques, studying on interactions between surface tension and micro-flows.In this research, three kinds of imaging methods for the three-dimensional micro-PIV have been developed. The first method is a stereo-imaging method using a pair of telecentric lenses, that enables parallel projection stereo matching. The second method utilizes digital inline holography technique. The stereo inline holography technique developed in this research consists of a simple optical setup and an easy calibration method. It improves spatial resolution along the direction of optical axis. The third method is the defocus method using color eccentric apertures that can process higher distribution density of tracer particles than the ordinary defocus method.The ordinary stereo imaging setup is known to be weak in vibration and needs delicate optical alignment, especially when it is applied to tiny objects. In order to avoid the problems, some one-camera stereo imaging methods are developed. The one-camera stereo method is far robust against outside vibrations.The dimensions of measuring objects are assumed to be from some tens to hundred microns. Flows in such small space are strongly influenced by the surface tension. The major interest of the present research is an influence of surface tension and the Marangoni flows in micro-channels. Experiments concerning to the issues had not been executed, since it has taken long time to develop the measurement techniques. More experiments should be done to study the influence of surface tensions on the micro scale flows in near future.Adding to the optical methods, the feasibility study of the three-dimensional PIV technique using X-ray has done for the advanced PIV in the synchrotron radiation facility, SPRING-8.