It is crucial to investigate the capillary driven flows along interior corners because of the interior corners of space fluid
management devices provide the main conduits for the transfer of fluids. In many instances, the interior corners are not
perfectly sharp but rather possess a degree of roundedness due to the design or fabrication. In this work, the problem of
capillary flows along rounded interior corners is revisited experimentally. Four test cells which are made of PMMA are
designed. The cross sections of the four cells are the same pentagon except that one 90° corners are rounded with
different radius <i>R</i>0 (sharp corner), <i>R</i>2.4, <i>R</i>4.8, <i>R</i>6, respectively. Four kinds of liquids are used in the microgravity drop tower tests, i.e. KF96-5 silicone oil, KF96-10, KF96-50 and Fluorinert liquid FC-70. The experimental results show that the advancing meniscus tip location of the fluid in the corner <i>L</i> (mm) is affected by container geometry and fluid
properties. These experimental results are valuable to better understand the capillary flow and also can provide scientific
guidance for the design and analysis of space fluid management systems.
The fluid flow associated with micro and meso scale devices is currently of interest. Experiments were performed to study the fluid flow in meso-scale channels. A straight flow tube was fabricated with 1.0×4.0mm<sup>2</sup> in rectangular cross section and 200mm in length, which was made of quartz for flow visualization and PIV measurements. Reynolds numbers were ranged from 311 to over 3105. The corresponding pressure drop was from 0.65KPa to over 16.58KPa between the inlet and outlet of the tube. The micro PIV was developed to measure the velocity distribution in the tube. A set of microscope object lens was mounted ahead of CCD camera to obtain optimzed optical magnification on the CCD chip. The velocity distributions near the outlet of the tube were measured to obtain full-developed flow. A CW laser beam was focused directly on the test section by a cylinder lens to form a small light sheet. Thus, high power density of light was formed on the view region. It is very important to the experiment while the velocity of the flow reaches to a few meters per second within millimeter scale. In this case, it is necessary to reduce exposure time to microseconds for PIV measurements. In the present paper, the experimental results are compared with the classical theories.
An optical diagnostic system consisting of the Michelson interferometer with the image processor has been developed for the study of the kinetics of the thermal capillary convection. The capillary convection, surface deformation, surface wave and the velocity field in a rectangular cavity with different temperature's sidewalls have been investigated by optical interference method and PIV technique. In order to calculate the surface deformation from the interference fringe, Fourier transformation is used to grating analysis. The quantitative results of the surface deformation and surface wave have been calculated from the interference fringe pattern.
An experimental investigation of Benard-Marangoni convection has been performed in double immiscible liquid layers of rectangular configuration. The two kinds of liquid are 10cst silicon oil and FC-70 respectively. The velocity fields in the vertical cross-section are obtained by PIV. Flow patterns and/or temperature distributions on the horizontal interface are displaced by using thermal color liquid crystal (TLC), and the velocity distributions on the interface were also obtained with the help of the serial particle image of TCL. The evolution processes of convection are observed in the differential thickness ratio of two liquid layers, and the convection styles are discussed.
In this paper, several techniques for fluid measurement, such as Optical Interferometry and Particle Image Velocimetry (PIV) etc. are introduced. And their applications on the fluid physics experiment of simulation microgravity on the ground in the national microgravity laboratory are presented. To reduce the gravitational effect on the ground, the character sizes reserached objects are generally very little. The measuring techniques of fluid mechanics have to be combined with micrology to carry out the measurement of little size.
The property of crystal depends seriously on the solution concentration distribution near the growth surface of a crystal. However, the concentration distributions are affected by the diffusion and convection of the solution. In the present experiment, the two methods of optical measurement are used to obtained velocity field and concentration field of NaClO<sub>3</sub> solution. The convection patterns in sodium chlorate (NaClO<sub>3</sub>) crystal growth are measured by Digital Particle image Velocimetry (DPIV) technology. The 2-dimentional velocity distributions in the solution of NaClO3 are obtained from experiments. And concentration field are obtained by a Mach-Zehnder interferometer with a phase shift servo system. Interference patterns were recorded directly by a computer via a CCD camera. The evolution of velocity field and concentration field from dissolution to crystallization are visualized clearly. The structures of velocity fields were compared with that of concentration field.
An optical diagnostic system consisting of the Mach-Zehnder interferometer with the phase shift device and the image processor has been developed for the study of the kinetics of protein crystal growing process. The concentration capillary convection around growing protein crystal was investigated during the process of trichosanthin crystal growth. The observation in real time showed that the concentration capillary convection associated with the surface tension of the crystallizing solution occurs at the vicinity of the surface of the protein mother liquor and directly affects on the outcome of protein crystallization, including the process of growth and the quality of resulting crystal. So far the detailed analysis and the important role of the concentration capillary convection in protein crystallization has been overlooked in both the space- and the ground-based crystal growth experiments. This may be one of the reasons for the majority of the results of space-based investigation shown no improvement.