Koh Ikeda

Combination of holographic interferometry and digital speckle system for measurement of density distributions

A digital speckle system has been combined with holographic interferometry to improve the accuracy of reconstruction of density distributions. For the combined system, several beam splitters have been used to separate the laser beams from a continuous-wave laser so that measurements can be performed simultaneously by both of the experiments. While the projections of the digital speckle system express the integration of the density gradients, those of the holographic interferometry can be obtained from the integration of the density itself. Thus, the steep region of the projections for the fringe shift of the interferometry has been measured by the use of the digital speckle system more accurately whereas the interferometry has been used to measure the projections for other regions simultaneously. CO2 flow from a rectangular nozzle has been investigated for the proposed combined system.

A technique for making holograms easily and for measuring simultaneously the behaviour of particles of different sizes and/or shapes

A new technique for rapidly discriminating shapes and/or sizes of micrometre size particles which are spatially distributed on a large scale has been developed. The technique is based on multiplexed matched spatial filtering, which is a kind of Fourier holographic filtering technique. Using the technique, large view visualization of the spatial distribution and the spatial behaviour of specific particles (e.g. aerosols, allergen particles, red blood cells, etc) can be realized. To make the multiplexed matched spatial filter (MMSF), a new material for hologram recording has been applied. The material is a photoconductor plastic which is processed by a solvent vapour and a corona discharge. The method of hologram recording is a dry process, which processes the material in several minutes at the initial settings of the device. Therefore, the MMSF can be made very easily in a short time. In the research, the discrimination of spatial behaviour of moving particles of different shape and/or size has been carried out by the MMSF made by the photoconductor plastic material.

Study on Two-Phase Flow Through a Micro T-Junction

The field of microfluidics is developing rapidly with advances in MEMS (micro electro mechanical system) and μ TAS (micro total analysis system) technologies. In various devices, controlling the flow rate of liquid or gas accurately at micro or nanoliter volume levels is required. In this work, the gas-liquid two-phase flow patterns in a microchannel T-junction have been examined. The two-phase flow patterns were observed in the T-junction under two different gas and liquid injection conditions. The flow patterns of liquid and gas in the microchannel after the T-junction were also observed and classified into three types depending on the flow rate, and a two-phase flow pattern map was constructed. The mechanism of bubble breakup at a micro T-junction was also experimentally and analytically investigated.Copyright

A Study on the Response of a Liquid Slug Pulled by a Ferrofluid Under the Influence of a Magnetic Field in a Microchannel

The field of microfluidics is developing with advances in MEMS (micro electro-mechanical system) and μ-TAS (micro total analysis system) technologies. In various devices, controlling the flow rate of liquid or gas accurately at micro or nanoliter volume levels is required. By using a ferrofluid, the flow of a liquid or gas in a microchannel can be controlled by the driving power exerted on the ferrofluid. In this study, an unsteady flow of a liquid slug caused by the driving force exerted by a ferrofluid has been investigated in a 200μm circular microchannel under the influence of an external magnetic field. The motion and behavior of the liquid slugs were observed. Thus, by visualizing the behavior and interface of the ferrofluid and the liquid slug, we could study the characteristics of fluid transport phenomena in the microchannel. The relationship between the movements of the liquid slug and the ferrofluid was investigated experimentally and analytically. The surface tension and kinematic viscosity of the liquid significantly affected the movement of the liquid slug. Therefore, the velocity of the ferrofluid is affected by the physical properties of the liquids pulled. Combinations of various liquids with a ferrofluid were examined in this study. The velocity of a short liquid slug was obtained and compared with the velocity of the ferrofluid. Also an apparent surface tension of the sample liquid was examined analytically.Copyright

Measurement of the jet Using Simplified HPIV

In this study, high spatial resolution measurement technique for three-dimensinal velocity distributions was examined. The Holographic Particle Image Velocimetry (HPIV) was the technique to record the three-dimensional position of the tracer particle on the hologram. From the 3 dimensional holographic particle images 3 dimensional velocity distribution could be calculated whith high-spatial resolution. Ordinaly the HPIV use the Phase-conjugated configuration to reconstruct the 3 dimensional particl position. Though with the technique the particle locations could be obtained with high S/N ration and high spatial resolution, the technique had very complicated caribration procedure and sensitivity. Therefore, in this study using the virtual image, more simple extracting technique to reconstruct particle locations were examined. The technique were simple in lyaout and had good S/N ratio and spatial resolution. Using the holographic particle images, 3 dimensional velocity could be obtained with high accuracy. In the experiment, the technique were applyed to measure upword air jet. The 3 dimensional particle locations were well extracted. Using the extracted particl locations, the 3 dimensional velocity could be calculated well showing the effectiveness of the technique.

Measurement of transient three-dimensional density distributions using photoconductor-plastic

The time sequential measurement technique for three-dimensional density distributions in a channel was evaluated. Using the holographic interferometer, information of the density distributions were visualized as fringes. In the real time method, the wave before disturbance is recorded on a hologram, then the hologram is developed at the initial set position. When the hologram is reconstructed, the fringes are caused by the interference between reconstructed wave of the undisturbed field and wave through the disturbed field. Since the reconstructed wave contains the information of the undisturbed field including the channel surface refraction, the fringe pattern represent only the optical phase changes inside the channel. However it is usually difficult to develop without movement or shrink. Using the photoconductor-plastic processed by solvent vapor, the hologram can be developed without any movement. In this study, buoyancy driven exchange flow of air and helium gas were measured using real time hologram with photoconductor-plastic. The transient three dimensional density distribution of buoyancy driven exchange flow are reconstructed, showing the effectiveness of the proposed technique.