Neutron radiography is one of radiographic methods, which makes use of the difference of attenuation coefficient of a neutron beam in different materials and has been used for many scientific and engineering applications. Since neutron radiography enables visualization of optically opaque fluid, it has been used for visualization and measurement of various multiphase flows. This paper reviews some of applications of neutron radiography to visualization and measurement of multiphase flows which have been performed in our laboratory.

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Recently, there are great requirements for ultra fine solid particles powder, in the fields of advanced materials, for example, electric parts in IT industry. Especially, the size control of fine powder is required. A jet mill and pneumatic classifier is used widely for the pulverization and classification of various kinds of fine particles in many powder manufacturing processes, respectively.
In pulverization by a jet mill, the improvement of pulverization efficiency is very important, because the jet mill consumes a large operating power. In classification by a pneumatic type powder classifier, there is no study on the flow characteristics which realizes a high performance for classification of ultra fine powder.
In this study, a new super sonic jet nozzle with a rectangular cross section is proposed and the flow and particle acceleration characteristics are investigated experimentally. It was known that the new super sonic jet nozzle has a high performance for improvement of pulverization efficiency.
A new pneumatic classifier is also proposed and the relation between the performance and the flow characteristics is investigated by flow visualization. The new classifier can classify ultra fine particles with sub-μm accurately.

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Experimental investigation was carried out on the flow patterns and rising velocity of gas phase in an ascending gas-liquid two-phase flow in an inclined pipe. Air and water were used as the working fluids, and the inclination angle was set to be 45°. The wettability of the pipe was varied by coating repellent on its inner wall. The boundaries between the bubbly flow, slug flow, and stratified flow regimes were not affected by the wettabiliy of the pipe. The boundary between bubbly flow and slug flow regimes was correlated as a function of the superficial velocities of gas and liquid. The rising velocity of gas phase increased as the wettability of the pipe became poor.

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Removal of gas from a gas-liquid mixture flowing downward in a circular pipe was investigated using an inversely placed Y-junction. One side of the Y-junction was coated with repellent to change its wettability. The wettability of this side became poor, while that of the other side was originally good. Experiments were carried out in two conditions. Firstly, the main pipe was inclined from θ=0° to 15° for the same initial water flow rates in the branches, where θ was measured from the vertical position. Secondly, the initial water flow rates in the two branches were set to be different values for a vertical pipe. In the inclined pipe the buoyancy force acting on the gas phase played an essential role for the gas removal. On the other hand, when the initial water flow rates in the two branches were different, the inertial force of water in the branches affected significantly the gas removal.

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This paper presents a scale model experiment on dispersions of automobile exhaust gas around street, in order to prepare reliable experimental data for the validation of available numerical methods. As a street setting, a simple roadside with buildings and/or an elevated highway was considered, and a wind blowing condition across the street was assumed. The scale model was arranged in a duct circuit filled with water. For the measurement of flow and concentration fields, some image processing techniques were used. Results seem to be qualitatively and quantitatively acceptable and will be applicable to the validation of numerical prediction methods.

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Shell and tube heat exchangers are among the most commonly used type of heat exchangers in the power generation, the chemical process, and the air conditioning industries. Shell-side cross-flow in tube bundles have received less attention due to the flow complexity and the measurement difficulty. In this study, the object was aimed to clarify the flow structure by obtaining velocity and temperature data in the whole flow area crossing the tube bundles with Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF). Experiments were conducted using two types of model of in-line and staggered tube bundle with pitch-to-diameter ratio is 1.50, containing 20 rows of five 15.0mm O.D. tubes in each row. Both velocity and temperature data in the entire flow field were measured successfully and heat transfer characteristics difference based on cross-flow structure between in-line and staggered array were clarified.

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Cold model experiments were carried out to understand the period and amplitude of swirl motions of a molten steel jet generated through a centered bottom nozzle. Cylindrical vessels of three different diameters were chosen. Water and silicone oil were used as the working fluids. Two types of swirl motions were observed. One appeared when the silicone oil layer was thin, and the water and silicone oil rotated in phase with each other. The other appeared at the interface between the two liquid layers when the silicone oil layer was thick. Empirical equations were proposed for the period and amplitude of the two types of swirl motions.

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The inverse analysis using Kalman's filter on the indentation load and depth curves measured by using a spherical indenter was carried out to identify the material constants: Young's modulus, yield stress, work hardening coefficient and exponent used in the constitutive equation given as power law. The advantage of the spherical indenter was shown by the simulation analyses using some material models. Uniaxial tensile tests using austenitic stainless steel and aluminum alloy were performed and compared with the analytical results using the constitutive equation with the identified material constants. As a result, it was confirmed that the presented technique is useful to identify the material constants of a sub-surface of materials and/or coating, etc.

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This paper is concerned with the tensile strength and strain rate of concrete materials by means of the experimental method of reflected tensile stress waves. The experiment is conducted by the Hopkinson bar technique and it is based on the superposition and concentration of tensile stress waves reflected both from the free ends of a striking bar and a specimen bar. The impact tensile experiment for concrete materials was carried out and the tensile strength of concrete under impact loadings was discussed as well as the effect of strain rates. This study focuses on the measurement of strain rates using both strain gages and crack gages. It is found that the impact tensile strength of concrete is remarkably influenced by strain rates ranging from 10⁰ to 1010² sec^-1.

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