In order to obtain the fundamental knowledge of free-surface flows under low-gravity conditions, the unsteady deformations of liquid surface in cylindrical vessels were experimentally observed with a drop tower. Main concern was focused on the dynamic behavior of the liquid driven by surface force and wetting, and the flow fields were found to be governed by the similarity rule described by Weber number. In addition, the algorithm of CIP-LSM, a numerical method for three-dimensional free-surface flows, was restructured on the basis of TCUP scheme, Level Set Method and MARS. The observed flow fields were also simulated by the developed code and the numerical results showed a good agreement with the corresponding experimental data.

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A novel approach to correct magnetic resonance phase contrast angiography (MR-PCA) based on the coupling computational fluid dynamics (CFD) to vessel segmentation in the level set methodology. MR-PCA data is supplied not only to partial differential equation based fast local level set vessel segmentation as the initial condition, but also to CFD code using level set ghost fluid method as the initial and boundary conditions. These procedures are integrated to provide with the corrected velocity field in the most optimal vessel geometry. The application of this system to both synthetic and clinical data are shown and validity is discussed.

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The direct numerical simulations (DNSs) of the turbulent Ekman layer over a smooth flat surface are performed. The Reynolds numbers are set to be Re_f=400, 510 and 600 where Re_f is defined by Re_f=G/√(((νf)/2)) with use of the Geostrophic wind velocity G, kinematic viscousity ν and Coriolis parameter f. The result with a higher Reynolds number of 600 shows a logarithmic region. However the slope is quite different from that of the turbulent Poiseuille flow because of its three-dimensional nature. The characteristics of the streak structure in the vicinity of the wall and large-scale structure in far upper region are discussed based on the obtained statistics such as premultiplied energy spectra. The effect of Reynolds number onto the large-scale structure is also discussed.

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The flow around a circular cylinder in surfactant solution was investigated in the Reynolds number range of 6000 to 50000 in several ways : by measuring the pressure around the cylinder, by visualizing flow and by measuring the velocity profiles in the wake. The test fluids were aqueous of the surfactant Oreyl-bishydroxyethyl-methyl-ammonium (trade name : Ethoquad O/12) with sodium salicylate added as a counterion. The pressure coefficient of surfactant solutions at the back of the cylinder was larger than that of tap water for Reynolds number above 6000. The separation point of surfactant solutions moves downstream, and the angle increases with surfactant concentration. The width of the velocity defect in the wake of surfactant solutions was less than that of tap water. For Reynolds number above 6000, a maximum drag reduction approximately 35% occurred with the surfactant solutions.

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It is important to understand an interaction between deformable surface and flow field surrounding it. In order to clarify this interaction, we had made some detailed experiments using several kinds of cylinder models having elasto-flexible surface in uniform water flow, and had found that on the surface were excited three different kinds of traveling waves, i. e. a continuously occurring wave, a periodically occurring wave and a randomly occurring wave. The present experiments were made to elucidate the mechanism of the wave generation and its propagation. The results showed that a relative frequency of the wave generation to that of the Karman vortex pair emission was linearly proportional to the power of 2/3 of the Reynolds number. This dependency is similar to the dependency of the wave propagation speed of Kelvin-Helmholtz instability in free shear layer on the Reynolds number. The traveling velocities of the waves were found to be about 65% of the main flow velocities regardless of the model diameter. Small vortices observed in the vicinity of the wave were found to move with same velocities as the wave propagating velocities. The velocity distribution in the shear layer of the separated flow around the cylinder was measured. The velocity at the inflexion point of the distribution was found to be same as the wave propagation velocity and the moving velocity of the small vortices. We concluded from the above results that the traveling waves were generated by the flow instability of the shear layer in the separated flow around the cylinder.

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In the previous paper, the authors have presented an active control method of surge occurring in a centrifugal compressor, using the control valve which is provided separately from the flow control valve. The surge control valve is operated with the plenum pressure as the feedback signal. In the present paper, the results of the numerical simulation of the surge control by the delayed feedback control are shown. The experimental measurements of surge control using a low flow rate centrifugal compressor have been done. The experimental and numerical results are described and it is shown that the proposed method is effective for control of surge of a centrifugal compressor.

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The behavior of single nitrogen gas bubble chains and the structures of flow field in the vicinity of a nozzle were experimentally studied. Both bubble diameters and bubble generation frequencies were precisely controlled independently to be 2.2 mm, and from 1 Hz to 10 Hz (corresponding bubble distance ; 300∼30 mm), respectively, by using innovative acoustic device. Careful investigations of flow field in the vicinity of a nozzle by using Particle Image Velocimetry enabled us to investigate the following two significant physical phenomena. First, The lift forces acting on bubbles in the bubble chains were observed to increase as bubble generation frequency increases, and were largely affected by the preceding bubbles. Second, developments of characteristic liquid jet were identified to play a dominant role in generation of lift forces on each bubble in single bubble chains, and were theoretically investigated by applying the conservation of liquid momentum.

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The flow velocity fields of swirl injector sprays for direct-injection gasoline engines were measured by using the PIV method. This method made it possible to measure not only transient and complicated spray droplet velocities but also the surrounding air velocity caused by spray formation and to analyze the mechanism of spray formation. In this study, two nozzles with different spray angles were used to analyze the effects of injection pressure and ambient pressure on spray properties and the results made clear the mechanism of spray formation. It was observed in particular that under a condition of high injection pressure (20 Mpa) with high ambient pressure, spray penetration after the injection period was longer than that obtained under low injection pressure (10 Mpa). This is attributed to both the higher spray velocity and the greater surrounding air velocity.

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Turbomolecular pumps (TMPs) coated with SiO₂ have relatively rough surfaces and give a higher compression ratio than non-coated pumps. In order to investigate the effect of the surface roughness on the pumping performance, the surface roughness was modeled by statistically located circular cone peaks and dimples of the same base radius and various base angles. The actual surface roughness of a blade was measured by SEM, and the obtained angle distributions were used to the surface roughness model. The effects of the surface roughness on the pumping performance of TMP were estimated by a two dimensional and a three dimensional Monte Carlo simulations. The calculated results were compared with the previously measured maximum compression ratios and pumping speed factors. The predicted results showed almost the same values as the experimental ones.

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Equations for evaluating the lateral-directional stability in steady rolling motion of high-speed for wing-in-ground-effect crafts were formulated. The crafts may consist of arbitrary number of wings within or out ground effect. Small perturbations superposed on the steady rolling motion of the craft were assumed and were linearized in comparison with the steady rolling motion. The parametric studies on the effect of sizes and locations of the vertical tails of the craft boats on the stability have given reasonable performances and tendencies.

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A model for predicting the noise level of cross-flow fans has been developed. In this model, the relative air-flow velocities on the outside of the fan's impeller are used. The model is based on two assumptions : noise levels are in proportion to the relative velocities at the edge of the blade raised to the sixth power and the velocities on the outside of the impeller have an especially close relation to the noise level. Well established computational fluid dynamics model is used to obtain the necessary velocity-field data for this model. The noise levels calculated by this model are in good agreement with the measured noise levels of a test impeller. This confirms that changes in the noise level with changes in the flow coefficient can be well described by the model. It is concluded from these results that this simple prediction model is a very useful tool for speeding up of the development of silent cross-flow fans, since relative velocity data is readily a vailable from frequently executed computational analyses.

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In this study, investigation of the effects of grid resolution and computational domain dependency on the DNS results of the wind-driven turbulent flow by means of direct numerical solution procedure for a coupled gas-liquid flow, i. e., MARS (Multi-Interfaces Advection and Reconstruction Solver) method, was conducted. Growing wind-driven surfaces, large computational domain size for the streamwise direction was demanded. On the other hand, the requirement computational domain size for the spanwise direction was closely linked with the typical wall turbulent structures consisted of the high and low speed streaks on the gas layer. The spectra of grown wind-driven surfaces follow the-4 power law. And the validities of the present DNS results, CASE 1 and 2 as the fully-developed wind-driven turbulent flows are revealed.

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The present paper has dealt with the one-sidewall cooling effect of spherical adsorbent paticles packed in a rectangular bed on water vapor adsorption characteristics by a 2-dimensional numerical analysis. The analysis model was considered that one-sidewall of a rectangular packed bed with the homogeneous spherical silica-gel particles was cooled and another walls were adiabatic. The moist air flowed into the rectangular packed bed with spherical adsorbent particles. The silica-gel B with high adsorption ability over high relative humidity was selected as a suitable adsorbent. Numerical results revealed the effects of moist air inlet humidity and airflow velocity, size of spherical silica-gel particles and width of the rectangular packed bed and the sidewall cooling terperature on the amount of water vapor adsorption.

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We investigated the characteristic of a heat-sink that was equipped with a high-power-density LSI package to study the influence of the heat-sink screws and flow-system of impinging air. Using the same volumetric flow rate, the pressure drop and thermal resistance of the heat sink with screws increased 10% and 5%, respectively, in comparison with the values obtained for the heat-sink without screws. Also, the pressure drop and thermal resistance of the heat sink with side impingement decreased 50% and 5-7%, respectively, in comparison with the values obtained for right-over impingement. In the side impingement, we obtained the same thermal resistance for the heat-sinks in changing the orifice width from 20 mm to 40 mm at the same pumping power about 1 W.

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Surface microstates of real surfaces of solid materials change in industrial environments, or they are changed in industrial surface processes positively. A real time diagnosis technique for the surface microstates should be developed for the process control. We propose a diagnosis technique for temperature and microstructure of real surfaces on a basis of the hardware performance of our wide-spectral-range high-speed spectrophotometer system. With respect to the temperature, an active spectral pyrometer technique is adopted, in which the reflection of the surface is measured as well as the self-emission. With respect to the microstructure, an attention is paid to the interference and diffraction of radiation in a new real surface model. An experiment is made on a metal surface in a high-temperature air-oxidation process to verify the performance of this technique. Spectra of emission and reflection energy of radiation in a near-infrared through infrared region are measured at every 2 s, and analyzed. Time transition of the surface temperature of an order of 1100 K is estimated within an inaccuracy of 10 K. The average thickness d and rms roughness σ₁ of the surface film are estimated to be in regions of d=0.08∼3.8 μm and σ₁=0.01∼0.71 μm, respectively.

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In order to investigate effects of adherent molecular characteristics and surface temperature on reaction probability and energy transfer to metallic surfaces, we carried out a classical molecular dynamics simulation by using LEPS potential energy surface between an oxygen molecule and a Ag surface. The surface reaction probability of oxygen molecules much depends on the characteristics of adherent molecules as well as the surface temperature. With the increase of adhesion strengh and mass of adherent molecules, both surface reaction probability and the average energy transfer to the surface in reflection cases decrease substantially. The relationship between surface reaction probability and surface temperature is much dependent on the characteristics of adherent molecules. When adhesion energy and mass of adherent molecules are small, the surface reaction probability increases with the increase of surface temperature.

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In this study, authors investigated the characteristics of auto-ignition/combustion of high pressurized hydrogen jets to improve performances of a direct-injection, diesel engine fueled with hydrogen. The experiments were conducted by simulating a diesel-like combustion field in a constant-volume combustion vessel. The objective of the study was to clarify physical and chemical effects on auto-ignition delay and heat release by changing the variables of injection pressure, orifice diameter, ambient gas temperature and ambient gas oxygen concentration in the experiments. The results show that auto-ignition delays of hydrogen jets are strongly dependent on the ambient gas temperature and that the ambient gas oxygen concentration has a weak effect on the auto-ignition delays. And it is also clarified that when the ambient gas temperature is relatively high, auto-ignition delays of hydrogen jets are almost the same for various conditions of ambient gas oxygen concentration and injection, but that injection conditions have a significant effect on the rate of heat release of hydrogen jets. It can be concluded that the mixture formation process plays an important role for the auto-ignition/combustion of hydrogen jets.

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In order to clarify the unsteady behavior and the quenching mechanism of the hydrogen-air premixed flame at a small circular hole made in the cooled plate put in the large container, the numerical calculation was carried out by using the detailed chemical kinetics. In this calculation, the stationary premixed gas is filled in the container at the start, and then the mixture is ignited at the end face and the flame propagates to the hole. At the hole, the flow is induced by the flame propagation and the heat is taken from the cooled wall, so that the flame front changes unsteadily and has the curvature. When the flame front has the curvature, the effects of non-unity Lewis number of the hydrogen fuel lean or rich mixtures appear in the quenching process. The relationship between the quenching diameter and the equivalence ratio are shown for the different thickness of the cooled plate. Moreover, the unsteady flame behavior and the critical quenching process are shown for the fuel lean and rich mixtures, and the quenching mechanism is examined so that the effects of the cooling and the Lewis number are charified.

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A swirling flow was produced in a vessel by tangentially charging fuel-air mixture or air. Rich fuel concentration was formed near the center of the vessel by fuel injection. Mixture was ignited at the center of the vessel. Various swirling flow field and fuel concentration field were made by changing the mean equivalence ratio in the vessel, the timing of charging mixture and fuel injection. The mean equivalence ratio in the vessel was changed from 0.20 to 0.84. Appropriate mixture stratification enabled initial combustion to be faster than that of homogeneous mixture. Under the lean condition, the combustion efflciency was lower and flame could not propagate in the lean mixture region near the wall as the homogeneity of the mixture became larger. In the case of the slowest swirling condition, initial combustion and initial flame propagation became slower due to rich mixture near the center of the chamber.

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Flow visualization measurement has been making use of measuring flow velocity in many fields. As in case of internal combution engine, gas flow in the engine deeply influences on combustion and heat transmission. The authors realized the flow visualization method using color layer, which can indicate the velocity to the depth direction of the image by color, and then three-dimensional measurement can be achieved. This paper shows the problems and solutions as to apply flow visualization by color layer to air flow measurement. One is the fabrication of trace particle being suitable for the color layer visualization. Another is obtaining the exact color information by solving the problems which happen as using a small tracer particle, and improving the method of image-processing. As a result, this newly revised visualization method make it possible to measure velocity of the particle within the error of 10%.

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Small-and-medium-sized gas turbines widely spread for distributed power and combined heat and power. However, most of their generating efficiencies are less than 35% because of simple cycle. Chemically recuperated gas turbine (CRGT) is an advanced cycle, which recovers exhaust heat by endothermic reaction converting fuel into hydrogen-rich gas, and several papers report that CRGT would be effective to improve generating efficiency of the simple cycle GT in feasibility study. Also, the CRGT using methanol steam reforming has been demonstrated, but the components and system operation has not been assessed technically in case of natural gas. In order to realize the CRGT with natural gas steam reforming, we applied the CR system to a commercial 4 MW simple cycle GT and surveyed effects of several parameters on the static mass and heat balance. On the basis of typical mass and heat balance, we also designed a heat recovery reformer by numerical analysis considering mass and heat transfer and chemical reaction.

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This paper covers our investigation into a decline in performance resulting from use of fuel containing impurities in methanol reforming type FCs. The investigations conducted and their results are as follows : 1) Various experiments and analyses were conducted to determine the adverse effects of CO, HCHO, HCOOH, and CH₄ on the performance of the FC ; 2) In the case of HCHO and HCOOH poisoning, performance became worse when Ru was added to the FC catalytic-electrode ; 3) The quantities of the partial pressure decline phenomenon of hydrogen gas caused by mixing CO₂ and N₂ gases appeared to be the same ; 4) The progress of poisoning with the reforming gas was complex ; however, explanation became possible by taking CO poisoning and the influence of the partial pressure decline phenomenon of hydrogen gas into consideration.

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