計測法

Neutron radiography (NRG) is a technique which produces images of the internal structure of a body, making use of the attenuation characteristics of neutrons in the materials being observed. Recently, attempts have been made to expand the application of this technique not only to non-destructive testing but also to a variety of industrial and basic research fields. The attenuation of neutrons is large in a light material like water and small in ordinary metals, which difference may make it possible to visualize a multiphase flow in a metalic container. Particularly, the neutron television, which is one of the applied techniques of NRG, is expected to be a useful tool for observing the behavior of two-phase flow, since it produces images in real time. In this paper the basic idea and the method of NRG are presented along with examples of visualization of multiphase flow by NRG.

Particle-Imaging Velocimetry (PIV) has advanced rapidly with the recent noticeable development of computers and image processors and the development and propagation of flow visualization techniques. The techique of PIV gives information on flow velocity, temperature and density through image analysis of visualized pictures and has been recognized as a strong new measuring tool in thermal and fluid engineering fields including multiphase flows. Its merits are: (1) simultaneous measurement of the whole flow field; (2) easy information processing of the other physical values from its measurement. Such merits are not shared by one point measurement methods such as the Pitot tube, hot wire anemometer and LDV. This article presents not only a general introduction of some methods of PIV but also some details of the fundamentals and applications of typical methods such as laser speckle technique, four consecutive time step particle tracking technique, the cross-correlation method using brigthness distribution patterns and the binary picture cross-correlation method using particle distribution patterns. Applications for these techniques are also suggested.

Blood flow rate in microvessels whose diameter is less than 100μm is an important factor in determining mass transport of oxygen, nutrients etc. as well as in determining production of biologically active substances such as nitric oxide. Several flow measuring techniques used for experimental microciculatory studies are reviewed. A dual-slit photometric method is a most widespread technique and has moderate temporal and spatial resolutions but it lacks a spatial resolution in the line-of-sight direction. A dual-window method using conventional video signals has a merit of simultaneous velocity measurements in multiple microvessels but its temporal resolution is inadequately low. A laser-Doppler method has sufficiently high temporal resolution to analyze pulsatile flow in small animals and fits for surface microcirculation of solid organs as well as transparent tissues. Image processing method of optical flow and a high-frequency pulsed-wave Doppler ultrasound method are promising in the near future.

This paper gives a brief survey from routine clinical methods to recent trend in the blood flow measurements. Dilution techniques, time-of-flight methods, electro-magnetic flowmeters, ultrasonic doppler methods, hot-film velocimeters, fiber-optic laser doppler velocimeters and whole-body methods are taken up, and their principles of measurements and their characteristics are explained.

Techniques for measuring velocity distribution in gas-liquid two-phase flow are important to elucidate the mechanisms of the flows in various two-phase systems, and to improve desigining industrial facilities. In this report, we focus on recent advanced techniques based on particle imaging velocimetry (PIV), which is known as a contact-free, multi-dimensional, instantaneous measurement tool. The current problems in applying the PIV to gas-liquid two-phase flows are summarized, and several examples of measured results are shown.

This paper presents a review on the state of current measuring techniques for gas-liquid multiphase flow rates.After briefly discussing the basic idea on measuring methods for single-phase and two-phase flows, existing methods for the two-phase flow rates are classified into several types, that is, with or without a homegenizing device, single or combind method of several techniques, with intrusive or non-intrusive sensors, and physical or software method. Each methods are comparatively reviewed in view of measuring accuracy and manageability. Its scope also containes the techniques developed for petroleum-gas-water flow rates.

Because “flow pattern” relates closely to design parameters of plant such as pressure drop and heat transfer coefficient, better knowledge of the flow pattern leads not only to deep understanding of the flow but also to accurate prediction of the parameters or to safe operation of plant. Therefore, “flow pattern” is an important and fundamental parameter as well as void fraction. Nevertheless the flow pattern has been judged mostly on a basis of visual observation. Therefore, it is desired to identify the flow pattern objectively and quantitatively.Here, identification of flow pattern using differential pressure fluctuations is described. Behaviors of statistical parameters are discussed in the statistical parameter spaces. And also recent flow visualization methods using fast X-ray CT and HPIV are described.

This report is a state of the art review of recent developments in measurement techniques for liquid film flows in gas-liquid systems. Our concerns are rapidly moving towards clarifying detailed structures of film flows in spatial and time domains dominating the mechanisms. This report focuses, along with typical conventional methods, recent advancements in film flow measurements mainly brought about by the developments in computer technologies, electronics and optics.

An ultra-fast X-ray computed tomography (CT) scanner has been developed for measurement of gas-liquid two-phase flow. This scanner overcomes problems that occur in a transient or unsettled state, which make the conventional CT scanner inappropriate. To reduce the scanning time, this X-ray CT system uses electronic switching of electron beams for X-ray generation instead of the mechanical motion adopted by conventional CT scanners. A prototype system with a scanning time of 3.6 milliseconds was initially developed and confirmed to measure the dynamic events of two-phase flow. However, an increased scanning speed is generally required for practical use in the thermal-hydraulics research field. Therefore, an advanced type which can operate under the scanning time of 0.5 milliseconds and can measure two-phase flow with a velocity up to 4-5 m/s was developed.

In this article, I will discuss the fundamental properties of particleswith particular attention to the recent development of measuring methods. Thediscussion is focused on the particle size and size distribution, mechanical properties, wettability, adhesive characteristics, and electrostatic properties. Other propertiessuch as specific surface area and zeta potential are also included.

To detect the flow rate of powder and bulk solids in pneumatic-conveying line, installing a solids flow meter at the inlet or outlet of the line is usual. If youput a gas-solids-2-phase flow meter instead, this can save installing space and cost, and make a completely enclosed system. As a matter of fact, usage of pneumaticflow meter which we developed, brought us such advantages. For yours reference, I would like to introduce you the flow meter, although its applications are not somany and its performance is not so perfect.

This review introduces the laser based measuring technique for both velocity of gas phaseand solid particle with particle sizing. Laser Doppler Velocimetry (LDV) has been the instrument ofchoice for measuring dispersed-and gas-phase velocities in particle-laden flows. LDV was used forsimultaneous measurements of continuous-and dispersed-phase velocities, which permits the particlesize discrimination based on light scattered intensity. Phase Doppler Anemometry (PDA) has beendeveloped for more precise size measurement for spherical particles. For non-spherical particles, diffraction intensity method for the equivalent diameter based on the projection area has been summa-rized. For the detection of particle shape, Shadow Doppler technique has been developed by the exten-sion of the optical system of Laser Doppler Velocimetry. Digital Particle Image Velocimetry (DPIV) is increasingly considered a proven technique for detecting both phases simultaneously. The author's group developed a measurement system to distinguish a dispersed-phase particle from a tracer in fluidflow. Several experimental results are presented in this review for gas-solid two-phase flow, such asjet, mixing layer and wall jet. Mean and Fluctuation velocities of both phases and volume concentra-tion of solids phase are given to make clear the turbulent structure of gas-solid two-phase flow.

Flow pattern of gas-solid two-phase flow is explained in horizontal and verticalpipelines based on a phase diagram where the pressure drop per unit length along the pipe isplotted against the superficial gas velocity with the mass flow rate of particle as a parameter. Conveyance limits are discussed for the horizontal and vertical upward flows. Dispersed flow, stratified flow, slug flow, plug flow and packed bed flow are qualitatively explained. As tothe method of flow visualization of gas-solid two-phase flow, we briefly review recent progressin laser sheet technique, and in tomographic methods by electrical capacitance and magneticresonance.

It is important to measure the volume solid concentration and solid concentration distribution of solids-liquid two-phase flow in pipes, since measuring these parameters contributes to make the mechanism of the flow clear and to control the condition of the flow. A review of the state of measuring techniques for the concentration and the distribution is presented in this paper. This report focuses on the typical conventional methods, probe method and image processing concerning the concentration and the distribution.

Solid-Liquid two-phase flows are frequently encountered in both industrial and global environmental fields such as chemical engineering, mechanical engineering, civil engineering, drift ice, icebergs and so on. Importance of the flows is growing in the above both fields. Measuring velocities of dispersed solid phase is essential for deep understanding of the flows. In this report, first, summary of measuring methods of the velocities is described.Second, simple and easy methods, namely probe method, and visualization of the flow fields and digital image processing, are discussed.

The optical fiber probe technique has been widely used in the analysis of gas-solid fluidized bed phenomena owing to the small size, quick response and flexibility of the probe as well as wide ranges of applicability of the technique as a whole. However, they give us only local information of the fluidized bed behavior and then it is hard to understand the macro phenomena in the fluidized bed. Therefore, multi optical fiber probe system and multifunctional optical fiber probe system were developed to clarify the macro scale analysis of the fluidized bed behavior. Also, a particle image scope consisting of an image fiber and a high speed video system was developed for micro scope observations of solid particles in circulating fluidized beds. In this article, we introduce the basic probe structures, examples of the obtained signals, analyzed flow behavior, single particle motion and particle collision patterns.

An ultrasonic computed tomography (UCT) developed for measuring time-averaged cross-sectional distributions of gas and solid concentrations in three-phase flow is described. The ultrasonic computed tomography is a coupling of a transmission mode ultrasonic sensor developed in Department of Chemical Engineering, Shizuoka University and a tomographic reconstruction technique based on dynamic neural network optimization algorithm developed in Department of Chemical Engineering, The Ohio State University. The ultrasonic sensor is based on measurements of the energy attenuation and the velocity change of ultrasonic pulse waves transmitted through the three-phase medium, enabling the measurements of the gas and the solid concentrations in the system simultaneously. The tomographic reconstruction technique has been proven to reconstruct simulated tomographic data accurately even with a very small number of projection data as used in the measurement. The application of the technique to a water-air-particles flow system in a bubble column is described.Glass-beads with diameters of 100, 260 and 350 micron meters are used as the solid phase. The time-averaged macroscopic flow structure and the behavior of the gas bubbles and solid particles distributions are investigated. The effects of gas velocity, solid loading and particle diameter to the behaviors of bubbles and particles distributions in the three-phase system are also discussed.

In industrial applications involving two-phase flows, the phase boundary information can be helpful in the design, control and safety of the flow process. Electrical impedance tomography (EIT) which has been hallmark in process tomography applications can be used to monitor these two-phase flows. This paper reviews various techniques for the estimation of phase boundary in two-phase flows using EIT.

Particle image velocimetry and ultrasound velocity profiling have around 25 years in history from their first appearance on literature. The early type of their instruments measures flows only at very slow speed in simple spatial structure. The rapid advances in computing tip above silicon cycle escalated them onto the stage of wide applications from fundamental study in fluid mechanics to major experimental tool for designing, managing, and evaluating of thermo-fluid phenomena. Extension to multiphase flow in the last decade is making their big news both in science and engineering researches. This article reports on the current topics and technical problems in multiphase flow toward next generation.

The lack of measuring techniques on complex multi-phase flows have restricted the studies within the observation of the flow patterns and the pressure drops with solids comparing those of air or water flow without solids or bubble loading. As a consequence of the progress in electronics devices and conventional laser sources which have become available with reasonable price for laboratory uses since the decade of 1980. The author will comment on the success and/or trap-pit in the measurements of several technical developments for particle and bubble flows.

This report presents a state of art of measurement technique of interfacial area concentration in a gas-liquid two-phase flow. Based on the conventional 4-sensor probe method, a simple algorithm was derived to measure bubble velocity assuming bubble shape. Measurement error in the bubble velocity and shape is caused by the interface curvature, which directly affects the measurement error of the interfacial area concentration. Correction method of interface curvature is shown to improve measurement accuracy of the interfacial are concentration.

This paper presents a micro-multiphase flow measurement technique using ‘multicolour confocal micro-particle image velocimetry (PIV)’ by wavelength separation technique. The present system can measure the dynamic interaction between flows in two different phases, such as liquid-liquid or solid-liquid, simultaneously and separately. The system has high temporal resolution up to 2000 frames per second, and high spatial resolution up to 0.116 μm/pixel in plane and 0.58μm out of plane, which is enough to resolve cell size measurement target.　In this paper, three measurement demonstrations are shown. There are flow inside and outside of moving microdroplet, droplet formation at T-shaped junction and red blood cells (RBCs) dispersed flow. The droplet is studied as a liquid-liquid multiphase flow using immiscible two liquids of oil and water. This study clarifies not only three-dimensional flow structure using continuity equation-assisted method, but also shear force between its interface. These informations are necessary for estimation of mixing effect using circulation in the droplet and discussion on droplet formation mechanism.　The measurement of RBCs mixed flow requires more due to its unsteadiness and randomness derives from characteristics of live cells. Our developed ‘Target-tracking system’ can measure one individual cell for long time under the high-magnification measurement condition. Finally the tank-treading motion of RBC and the surrounding flow structure simultaneously for the investigation of specific behavior of RBC.

This paper presents mainly a review of measuring techniques for multiphase flows in the past 30 years and an outlook of future progress on distributed measuring systems. Laser based measuring system had started by point measurement such as a probe, laser Doppler, and Phase Doppler anemometry, and then extended to Particle Imaging techniques to obtain 2D plane information. Recently, high speed digital cameras allowed us to get 3D3C temporal velocity information. The possibility of IoT based distributed sensing system is discussed with an application of multiphase flow analysis for future developments.

For playing a role of filling a hole in the applicable range of standard rheometer, ultrasonic spinning rheometry (USR) is presented; it is based on equation of motion to explain the fluid rheology and to quantify the rheological properties satisfying the considered equation of motion for complex fluids. Some examples of rheological evaluation for multi-phase fluids using USR were presented; clay dispersion with thixotropy, polymer solution with large-spherical particles, dessert paste with pectin gel including fruit pulps. The efficacy of USR was discussed through those practical tests for complex fluid.

In the continuous casting process, argon gas is injected into the tundish to homogenize the molten steel and remove the undesired inclusion. Furthermore, the molten steel flow is controlled by applying a magnetic field to the mold. The inclusion of argon gas as the molten steel flows into the mold can lead to product defects. Therefore, it is essential to predict the motion of the bubble in liquid metals under influence of the magnetic field, and further investigations are required for the liquid-metal two-phase flows. However, measurement techniques which can be applicable to opaque fluids such as liquid meat are limited. The authors have developed a high-speed ultrasonic tomography for measuring bubbles motion and investigated the behavior of continuously released bubbles motion in gallium alloy under influence of a horizontal magnetic field. The ultrasonic tomography measurements were carried out with 500 frames per second. It was shown that as the magnetic field strength increases, the variation of the bubble passing position in the measurement cross-section becomes smaller. Furthermore, it was confirmed that the distribution changed slightly depending on the direction of the applied magnetic field and that the bubbles tended to distribute in the direction perpendicular to the magnetic field. This trend changes depending on the difference in the gas flow rate. It is thought that the greater the influence of the wake, the more pronounced the anisotropy of the distribution.