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

本研究的目的是：1)发展能够测量微尺度流场中瞬时三维速度分布的测量技术；2)利用发展的技术，研究表面张力与微流场之间的相互作用。第一种方法是使用一对远心透镜的立体成像方法，该方法能够实现平行投影立体匹配。第二种方法是利用数字同轴全息技术。本研究开发的立体同轴全息技术包括一种简单的光学装置和一种容易的校准方法。提高了光轴方向的空间分辨率。第三种方法是利用彩色偏心光圈的离焦法，它可以处理比普通离焦法更高的示踪粒子分布密度。众所周知，普通的立体成像装置振动小，需要精密的光学对准，特别是在应用于微小物体时。为了避免这些问题，人们发展了一些单摄像机立体成像方法。单摄像机立体法对外界振动有很强的抵抗力，被测物体的尺寸被假定为几十微米到几百微米。在如此小的空间中，流动受到表面张力的强烈影响。本研究的主要兴趣在于表面张力和微通道中的Marangoni流动的影响。由于测量技术的发展已经花费了很长的时间，所以没有进行关于这些问题的实验。在不久的将来，表面张力对微尺度流动的影响还需要进一步的实验研究。在光学方法的基础上，对同步辐射装置SPRING-8上的先进PIV进行了X射线三维PIV技术的可行性研究。

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.