Laser-Induced Liquid Jet (LILJ) is a promising surgical knife because it reserves blood vessel and emits less heat. LILJ is ejected at high speed by shock wave and expansion wave caused by the pulsed laser focusing. In practice, strong shock and expansion wave bring elastic deformation of the thin tube wall as well. In this study, we try to develop a numerical model to analyze the effect of wall elasticity in jet formation. A simple model that can be implemented as a boundary condition into an existing algorithm for two-phase flow simulation is proposed. The model has been validated in the simulation of an oscillating high pressure channel with steel and acrylic walls. The wall displacement and the wall pressure are resolved well with a good spatial and temporal convergence. In the simulation of LILJ based on the elastic wall model, it was found that a low pressure zone may appear in a short duration in the tube, and the shape of the water jet agrees better with experimental results than that based on the rigid wall model.

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The unused biomass such as residues left on forest floor and unused portions of farm crops is considered as the most promising domestic resources in Japan. The utilization of unused biomass contributes to the environmental protection of forests as well as the reduction in exhaustion of carbon dioxide. To promote the utilization of woody biomass generated in forests and hilly agricultural areas, the efficiency for the transportation across hilly district regions has to be improved. In the present study, the hydraulic transportation system of wood chips by means of liquid film flow in sloped pipeline is proposed. The transportation limit of wood chips with various aspect ratios is investigated by using the test section imitating the hilly terrain pipeline. The results obtained are as follows. The maximum flow rate of wood chips is caused by the occurrence of hydraulic jump in horizontal flow, and is greatly affected by the liquid film flow rate and aspect ratio of wood chips. The analytical model to predict the stagnation of wood chips is presented, and it is found that the model gives a fairly good agreement with the experimental results of maximum flow rate of wood chips.

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We have investigated various problems that arise in applying the Brownian dynamics method to a suspension composed of rod-like hematite particles, which have a magnetic moment normal to the particle axis direction. The accuracy and the deviation of simulation results from theoretical solutions have been discussed by comparing with the theoretical results that were obtained by solving the basic equations of the orientational distribution function. The characteristics of the negative viscosity is not observed to be dependent on a time interval unless a sufficiently short time interval is used. The present simulation results can well qualitatively reproduce the characteristics of the negative magneto-rheological effect that was predicted by the previous theoretical investigation. Quantitative agreement is good in the range of small applied magnetic fields, but it is not good in the large magnetic field areas. The deviation of the negative viscosity from the theoretical prediction cannot be improved by making a numerical algorithm more accurate from Euler to 2nd-order or 4th-order Runge- Kutta algorithm. The results of the orientational distribution can well reproduce the characteristic features that the distribution has gradual shape with a low linear-like peak, which is in significantly contrast to a sharp one-peak-type distribution of a ferromagnetic rod-like particle dispersion. The present orientational distributions are in significantly good agreement with those of the theoretical prediction in regard to the position and the height of a peak and the whole shape of the distribution. Good agreement of the present magnetization curves with the theoretical prediction verifies that the spin rotational Brownian motion is activated at a physically reasonable level.

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The scaling laws of streamwise turbulent intensity and turbulent energy spectrum profiles have been investigated experimentally for the approximate equilibrium boundary layer subjected to an adverse pressure gradient. Non-dimensional pressure gradient parameters P⁺ and β are 2.74×10^-3 and 1.32, respectively. The momentum thickness Reynolds number R_θ is 10,200. The velocity scales u_es derived analytically from the boundary layer equation and u_s a limiting case with respect to P⁺→0 of u_es are used instead of the friction velocity u_τ. Streamwise and normal turbulent intensity profiles scaled with u_s collapse on those of zero pressure gradient case. With experimental data by Monty et al., the streamwise turbulent intensity scaled with u_s and u_es takes almost constant value to P⁺ in the local similarity region for 0≦ P⁺ <3.00×10^-3 and 0≦ P⁺ ≦6.17×10^-3, respectively. Also, turbulent energy spectrum in the inertial sub-range are well scaled with u_s rather than u_τ. Accordingly, it is expected that u_es and u_s are suitable for the scaling of the turbulent intensity and turbulent energy spectrum.

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An impulsive pressure wave (micro-pressure wave) emitted from a tunnel portal is one of the environmental problems in high-speed railways. The magnitude of the micro-pressure wave is approximately proportional to the maximum pressure gradient of the compression wavefront at the tunnel portal. Consequently, it is necessary to investigate the compression wave generated when a train enters a tunnel for estimating and reducing the micro-pressure wave. In this study, the generation of the compression wave by a train entering a tunnel is investigated by model experiments. The train, tunnel and ground are represented by a three-dimensional model with a ground plate, a mirror-imaged three-dimensional model and an axisymmetric model. The experimental results indicate that the distance between the train center and the center of the tunnel base is a significant parameter for the estimation of the compression wave in the tunnel generated by the train entry. Furthermore, the model experiments with three-dimensional model can improve the accuracy of the estimation of the compression wave even if the train nose is equipped with parts having sharp edges like a snowplow.

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Velocity potential, kinetic energy and added mass of a cluster of straightly in-line spherical and unequal constant-volume bubbles moving with different velocities in an incompressible liquid are analytically obtained in the framework of potential theory. Mutual interaction among the bubbles is taken into account in the analysis up to the order of (a_i/L_ij)³, where a_i is the radius of bubble i(i = 1, 2, 3, ··· , N) and L_ij( j ≠ i, j = 1, 2, 3, ··· , N) is the central distance of bubbles i and j. For special cases of a single and two bubbles, the velocity potential, kinetic energy and added mass in the present result are identical with those known well for the same cases. The added mass of the cluster of equal bubbles with the same inter-bubble distance and velocity largely decreases in dependence on the ratio of a_i/L_ij and the number of the bubbles.

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This paper describes effects of microbubble injection on natural convection heat transfer from a vertical heated plate in water. Thermocouples are used for the temperature measurement and an image processing technique is used for obtaining the bubble diameter, the bubble velocity and the bubble layer thickness. The working fluid used is tap water, and hydrogen bubbles generated by electrolysis of the water are used as the microbubbles. For a constant bubble flow rate and a constant wall heat flux, in the laminar and transition regions, the heat transfer coefficient is significantly increased by the microbubble injection (The ratio of the heat transfer coefficient with bubble injection to that without injection is 1.6-2.0 in both regions). The heat transfer enhancement in the laminar region results from both the forced-convection and mixing effects due to microbubble injection. On the other hand, the heat transfer enhancement in the transition region is mainly affected by acceleration of the transition to turbulence due to microbubble injection.

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In order to achieve higher heat transport performance for electronic power device cooling, a two-phase heat transport device with parallel tubes, which consisted of several thin tubes connecting cooling- and heating-headers, was developed and its performance was experimentally tested. The performance of the parallel-tube heat transport device was higher than that of the meandering closed loop heat transport device of self-existing mode oscillating flow. In this study, in order to clarify the effects of various parameters on the heat transport performance, experiments were performed by varying the following parameters: working fluids, filling ratio, number of tubes, tube diameter and length, header diameter, and temperature difference between heating and cooling headers. In addition to the heat transfer experiments using copper circular tubes, flow visualization experiments were performed using square channels grooved on a plate. These results show a detail of the parallel-tube heat transport device performance. The heat transport limit occurred by dry-out in the heating header.

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In this work, the authors have studied a method for the improvement of the generating efficiency of a gas-turbine combined-cycle system (GTCC) using by-product gas (pretreated blast-furnace gas). The generating efficiency of by-product-gas-fired GTCC is 7 % lower than that of LNG-fired GTCC at a combustion temperature of 1623 K. The generating efficiency of the gas-separation energy was improved by +5.5 % (η=48.8→54.3 %) by removing CO₂ and N₂ from the blast-furnace gas. If this innovative system were applied to steelworks around the world, the potential electricity generation would be 69 billion kWh/year. This would mean a reduction of Δ56 million t-CO₂/year.

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In this study, experiments were performed to measure the thickness of the liquid film formed between the heating surface and the vapor bubble with the laser extinction method for the gap size of 0.5, 0.3 and 0.15mm.Water, toluene and HFE7200 were used as test fluids. It was found that the gap size and bubble forefront velocity determined the initial thickness of microlayer no matter of the kind of testing liquid. Vapor bubble generated by boiling in the present mini-gap grows exponentially due to the rapid evaporation of the thin liquid layer, which makes the phenomena highly transient as opposed to the steady situations considered before. Based on the experimental data and scaling arguments a non-dimensional correlation in terms of capillary number and Bond number is proposed.

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A liquid fuel injection nozzle with a novel fuel atomization strategy which actively utilizes the effect of collapse of cavitation bubbles in a liquid jet is proposed. The nozzle comprises two orifices and an intermediate cavity between the orifices. The role of the upstream first orifice is to generate the cavitation bubbles at both inlet and exit of the orifice. The intermediate cavity is placed to hold the cavitation bubble within it. The role of the downstream second orifice is to mix the cavitation bubbles and liquid fuel, and to inject the mixture into atmosphere. Each size and relative positions of the first orifice, the intermediate cavity and the second orifice were studied using multi-phase computational fluid dynamics. Finally, a poppet type nozzle whose void fraction at the nozzle exit is 0.5 was designed.

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A poppet type nozzle which promotes atomization by utilizing cavitation phenomena was designed to clarify the atomization mechanism. The configuration of the nozzle which has two orifices and an intermediate cavity between the orifices was decided by numerical analysis on the cavitating flow in the nozzle. In this report, atomization mechanism and spray characteristics of the nozzle are described. The following results are obtained: (1) The net-like fuel liquid sheet is observed closed to orifice. The net-like structure with cavitation bubbles is collapsed to droplets via ligaments. (2) The present nozzle has the features of generating smaller drop size and lower spray tip penetration than the conventional poppet type nozzle.

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In the present study, we report on the effect of double diffusive convection associated with solute discharge in the early stage of unidirectional solidification from above. Two-dimensional numerical simulations have been conducted to clarify the concentration, temperature and heat flux on the solid-liquid interface under a constant solid layer growth rate. The moving boundary due to solid layer growth was formulated according to the boundary tracking method. The simulations were conducted by varying the initial conditions; concentration, solid layer growth rate and heating temperature at the bottom. The effects of thermal and solutal Rayleigh number on the concentration and the convective heat flux at the solid-liquid boundary were discussed, and the associated correlations to predict those values as functions of the initial thermal and solutal Rayleigh numbers as well as the speeds of solidification were derived.

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Deposition characteristics of JetA-1 containing various fatty acid or their methyl esters were investigated experimentally. Test fuel was JetA-1 to which 10wt% of a certain fatty acid or methyl ester was added. In deposition test, single droplet of test fuel was dripped on a hot surface repeatedly, and evaporation deposits formed on it were analyzed. As a result, the mass of deposits formed from the test fuels were much larger than that formed from pure JetA-1. Moreover, it was found that the deposition mass increased with increasing the degree of unsaturation of fatty acid which was added to JetA-1.

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The purpose of this study is to improve atomization characteristics of a direct injection Diesel nozzle, which spray with large spray angle, short liquid core length and small droplet diameter are obtained. In the previous study, the single hole atomization enhancement nozzle, which excellent spray characteristics are obtained at relatively low injection pressure, was developed. In this study, it was investigated about atomization of spray of the multi-hole atomization enhancement nozzle, and aimed to improve atomization characteristics and to obtain excellent spray characteristics. Effects of dimensions of the atomization enhancement nozzle, such as geometric shapes of nozzle hole and hole diameter, on atomization characteristics were investigated. As a result, it was cleared that in case of the multi-hole nozzle with hole number of N=4, breakup length becomes short and spray angle becomes large about two times compared with the actual single hole nozzle. Atomization characteristics of intermittent injection were improved considerably by using the multi-hole nozzle with round inlet shape of nozzle hole and the multi-hole nozzle with hole number of N=4 at high-ambient pressure conditions for actual Diesel engine.

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This study is performed to experimentally examine the fundamental burning velocity characteristics of meso-scale spherical laminar flames in the range of flame radius r_f approximately from 1 to 5 mm for hydrogen-oxygen mixtures diluted with Ar, CO₂ or N₂, in order to make clear an influence of dilution gas on burning velocities of meso-scale flames and a method for improving combustion of micro-meso scale flames. Macro-scale laminar flames with r_f > 7 mm are also examined for comparison. The mixtures have nearly the same laminar burning velocity for unstretched flames and different equivalence ratios φ(=0.5-0.9). The radius and the burning velocity of meso-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It is found that the burning velocities of meso-scale flames for CO₂ diluted mixtures (φ=0.5-0.9) have a tendency to decrease with increasing r_f, and approach those of macro-scale flames. Such a trend, however, can not be seen for Ar- as well as N₂- diluted mixtures of hydrogen and oxygen with φ=0.7 and 0.9, whose burning velocity of meso-scale flames can not be explained based on that of macro-scale flames. This suggests that micro-meso scale flames have the optimum size and Karlovitz number to improve the burning velocity, depending on dilution gas types in addition to φ and fuel types.

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Relevant to materials synthesis by combustion, not only spontaneous ignition of compacted mixture but also flame propagation just after the ignition has been examined for Ti-Al system with rectangular shape. Not only experimental but also theoretical study has been conducted, after confirming that the size ratio, defined as the ratio of compact thickness and particle diameter, can be useful parameters in correlating experimental results. It is found that with increasing size ratio, the spontaneous ignition comes to occur below the melting point of Al (934 K), due to an increase in the particle surface per unit spatial volume of compacted mixture. Effects of mixture ratio and/or degree of dilution on the spontaneous ignition temperature have also been examined. In addition, effects of various system parameters on the burning velocity just after the ignition have been examined. Experimental comparisons with theoretical results have also been conducted and a fair degree of agreement is demonstrated, indicating that the formulations referred to have captured the essential features of the spontaneous ignition of compacted mixture and the SHS flame propagation that passes through it. Since this kind of particle size effect, especially, relevant to the spontaneous ignition and the flame propagation after the ignition, has not been captured in the previous studies, its elucidation can be considered not only notable but also useful, especially, in manipulating combustion process in materials synthesis.

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In the present study, we reveal the dominant chemical reactions and the optimum conditions, supposing the design of ethanol steam-reforming reactors. Experiments are conducted for two types of catalysts; namely, Cu/ZnO/Al₂O₃ and Ru/Al₂O₃. Using a household-use-scale reactor with well-controlled temperature distributions, we compare experimental results with chemical-equilibrium theories. As a result, the Cu/ZnO/Al₂O₃ catalyst shows rather high performance at low reaction temperature T. This implies that the Cu/ZnO/Al₂O₃ catalyst promotes the ethanol-steam-reforming and water-gas-shift reactions, but doesn't promote the methanation reaction. On the other hand, such high-reaction-temperature-type catalysts as Ru/Al₂O₃ promote all the three. Furthermore, we specify the effect of steam-carbon molar ratio S/C on the hydrogen concentration C_H2, and the effect of T on C_H2, for each catalyst.

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