In recent years, the heating value of CPU has been increasing rapidly with the improvement of computer performance. Therefore computer industry is requiring cooling unit with high cooling performance for CPU in applicable to high heating value and heat flux. The existing cooling unit for CPU has been air-cooling aluminum fin, however it can not be adaptable to high heating value. We have developed a new compact boiling refriberant type cooling unit for CPU. In this paper, the basic cooling performance of this boiling refrigerant type cooling unit was evaluated, it was clarified that the boiling refrigerant type cooling unit has high cooling performance compared with conventional air-cooling aluminum fin. Furthermore the calculation method for predicting the cooling performance by modeling boiling and condensing phenomena was proposed.

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Optimization of fin arrangement in a metal hydride (MH) bed has been sought with calculations to enhance heat transmission in a hydrogen storage tank and get the maximum hydrogen absorption rate. Two different fin configurations such as radial and circular fins in a vertical cylindrical reactor vessel using a La-Ni based AB 5 type hydrogen storage alloy were tested. Two dimensional transient heat conduction analysis in the bed coupling with exoergic hydriding reaction predicted temperature and absorption of hydrogen. Those agreed with some experimental results within 6 K and 8.5%, respectively. Hence effects of thickness, spacing and shape of fin on hydrogen absorbing rate were analytically evaluated and optimum range of the each fin arrangement was decided according to a trade off between absorption time and reduce of the MH volume due to the fin volume. At most the hydrogen absorbing time for the recommended fin layout may reduce to about one-third of that without fin.

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The flow around a rotating elliptic cylinder in a uniform flow was investigated by conducting a wind-tunnel experiment by use of PIV method and by a numerical analysis based on the finite volume method. The experiment was carried out at the same velocity and rotational frequency of autorotation of an elliptic cylinder falling in the air. The numerical analysis reproduced typical flows such that the rotating elliptic cylinder shed vortices around itself. The time variations of the drag and lift coefficients of the cylinder were obtained from results of the numerical analysis and were compared with those determined from the potential flow theory.

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In this paper, a novel insect flight model based on fluid-structure interaction is proposed. Incorporating the high compliance of the wing base, which is observed in Diptera, the proposed model can express the automatic control of the wing rotation via fluid-structure interaction and can generate the adequate aerodynamic forces for the insect flight. The fluid-structure interaction is simulated by a monolithic method based on the finite element method. The result given by the proposed model is investigated by comparison with experimental results of the dynamically scaled model of the fruit fly given by Dickinson et al.

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This paper proposes a two-dimensional vortex method, based on Vortex in Cell method, for gas-liquid two-phase free turbulent flow. The behavior of vortex element and the bubble motion are calculated through the Lagrangian approach, while the change in the vorticity due to the bubble is analyzed in the computational grids resolving the flow field. Therefore, the numerical procedure corresponds to the Lagrangian-Eulerian method. The present method is applied to simulate the bubbly flow around a square-section cylinder. The simulation demonstrates that the bubble entrainment into the Kármán vortex and the resultant reduction for the strength of the vortex are successfully captured by the method. It is also confirmed that the vortex shedding frequency and the pressure distribution on the cylinder are favorably compared with the measured results.

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The purpose of this study is to propose a numerical simulation method for predicting unsteady deformation of structures in response to unsteady changes of fluid dynamic force acted on them. The numerical simulation is carried for elastic structures with weakly coupling a finite difference fluid solver and a finite element structure solver. An overset grid technique and a space-time finite volume technique are used in the fluid solver. In the finite element structure solver, kinetic nonlinear effects of the structures from large displacement, large rotations, and large strains are considered. A typical numerical simulations is carried out for vortex-induced vibrations of an elastic elliptic cylinder. The proposed method could be useful for the prediction of the periodic deformation of the structure under the vortex-induced vibrations.

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Simulations with Lattice Boltzmann method are conducted for particulate suspension in a plane channel flow at low and moderate Reynolds numbers to investigate blood cell behavior in microvascular flows. The simulation results for three kinds of hematocrit indicate existence of an important relationship between the Reynolds number and the variance of the particles. When the hematocrit is small, it is found that the particles are concentrated between the centerline and the wall, that is, Segré-Silberberg effect appears. As the hematocrit becomes larger, on the other hand, this effect disappears and the variance of the particles is increased. In the case of an inelastic collision, the particles which flow near the wall are increased in comparison with the case of the elastic collision.

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To develop a simulation software which is able to predict the molding flow of polymeric liquid crystals, we present a basic model and its computational procedure. The flow is modeled by the Transversely Isotropic Fluid theory, which is equivalent to the Leslie-Ericksen equations in the high viscosity limit. In the modeling, the Hele-Shaw approximation is applied in order to reduce computational power. Finite difference technique is used to solve governing equations except for the angular momentum equation, which is solved by the streamline integration method. Two thin molds with simple shape are selected to evaluate the model. The computational results for locations of flow front, temperature and molecular orientation profiles show that the model can predict smooth molding process and that molecular orientation depends largely on the position in the gap direction. Since alignment of molecules is disordered by the occurrence of tumbling, which depends on fluid temperature and shear strain, mold temperature and gate position are important for effective molding.

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Mach number of shock wave propagating in a pipe is usually estimated by techniques using an average velocity of shock, a pressure history, etc. Mach number obtained from the pressure histories of the shock propagating between two stations is the averaged one between the stations. To obtain a local shock Mach number at a certain station, the pressure jump across the shock from a single pressure history is often used. In this case the pressure history is filtered, which makes it difficult to evaluate the local Mach number correctly. In this paper a dynamic characteristic of the pressure transducer is examined and a step response of pressure is utilized to obtain the local Mach number.

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In order to increase the safety and reliability of ropeway systems, it is extremely important to improve windproof performance of carriers since the excessive swing of the carrier by wind may lead to a serious accident such as a collision with the columns. As the first step of studying improvement of windproof performance of ropeway carriers, this paper presents analysis results of accidents due to wind and results of wind tunnel experiments of real carriers. Analysis results of accidents clarified features of ropeway accidents due to wind. Results of wind tunnel experiments showed aerodynamic characteristics of two typical monocable carriers.

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In order to increase the safety and reliability of ropeway systems, it is extremely important to improve windproof performance of carriers since the excessive swing of the carrier by wind may lead to a serious accident such as a collision with the columns. As a means of improving the windproof performance of ropeway carriers, this paper presents aerodynamic method using additional aerodynamic devices such as fairing device and wing device. The results of wind tunnel tests showed the good effects of lower fairing device and semioval wing device on the aerodynamic characteristics of a carrier.

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The pressure-sensitive paint (PSP) has potential as a diagnostic tool for pressure measurement in the high Knudsen number regime because it works as a so-called “molecular sensor”. However, there are few reports concerning application of the PSP to micro devices because the conventional PSP is too thick owing to the use of polymer binder. In this study, we have adopted Langmuir-Blodgett (LB) technique to fabricate pressure sensitive molecular films (PSMFs) using Pd (II) Octaethylporphine (PdOEP) and Pd (II) Mesoporphyrin IX (PdMP), and have tested these PSMFs to evaluate the feasibility of the pressure measurement around micro-devices. It is clarified that the PSMF composed of PdMP has higher sensitivity than that of PdOEP. Since it is also considered that the sensitivity of PSMFs can be increased by introducing arachidic acid as the spacer molecules to prevent the aggregation of luminescent molecules, we have produced PSMFs with several molar ratio of PdMP to arachidic acid. At the most suitable ratio, the PSMF has sufficient sensitivity in the low pressure region with high Knudsen number, even if the amount of the luminescent molecules in the PSMF layer is smaller than those in conventional PSPs. This indicates that the PSMF is feasible to measure the pressure in high Knudsen number flows such as micro-flows.

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A computer simulation using particle method was carried out to investigate effects of deformabilities of red blood cells (RBCs) on blood flow in microcirculation. The motion of deformable RBCs was determined by the spring model on the basis of the minimum energy principle. The motion of the plasma fluid particles was analyzed by the moving-particle semi-implicit (MPS) method assuming incompressible viscous flow. The two-dimensional simulation of blood flow between parallel plates demonstrated that RBCs moved downstream and were deformed into a parachute shape as observed in experiments. Comparison between the results for single RBC and multiple RBCs clarified that the deformation of RBCs was suppressed by their neighboring RBCs. The higher the spring constants of the RBC model, the less deformed the RBCs were, causing large blood flow resistance. These results indicate that deformability of each RBC cooperates with mechanical interaction between RBCs in determining the rheological properties of blood on blood cellular scale.

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Butterfly-type flapping flight was defined by a low flapping frequency, low wing loading and large wingspan. On the basis of the definition, we made a butterfly-type ornithopter (BTO). The BTO has no stabilizing device such as a tail fin, however, it flew stably when the position of the center of gravity was appropriate. Flights of the BTO were recorded with a high-speed video camera, and its longitudinal motion was measured. In the stable flight, angle of attack of the body α_body varied coincidentally with a flapping cycle. To reveal the effect of the change of α_body on aerodynamics, we visualized the air flows around the wing of the tethered BTO for several values of α_body. When α_body is positive, leading edge vortex (LEV) was attached to the wing during downstroke, and it separated from the wing when α_body was too large. We also visualized the air flow around the free flying BTO. In this case, α_body was large in the beginning of downstroke, however, LEV was not separated from the wing during downstroke due to the rapid decrease of α_body. This result suggests that butterflies are designed to take advantage of passive change of α_body.

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Jets issuing through small holes into a freestream have proven effective in the control of boundary layer separation. The beneficial effect of separation control is obtained only if the jets are pitched to the lower wall and skewed with respect to the freestream direction. In the previous study, the suppression effect of the orifice shape on flow separation was reported for three types of jet orifice (circular, triangular and square orifices). The triangular orifice generates the strong vortex and makes effective the pressure recovery in the diffuser in comparison with the circular and square orifices. In this study, four types of the jet orifice (model-U, model-D, model-R and model-L) are installed and the effect of the direction of the vertex of the triangular orifice on separation control is investigated in a two dimensional diffuser. Separation control is accomplished by all models, however the suppression of flow separation is most ineffective among the four models in the case of model-L (the vertex points to the direction of the jet pitch angle).

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In the early 1970s, the issue of whether propulsion in swimming is due primarily to lift or drag appeared. Prior to that time it was believed that the best way to propel the body forward was to pull the hand directly backwards to use drag forces. Furthermore, the actual motion of a hand in swimming is obviously unsteady and the time-dependent fluid forces have to be taken into account. In this study, unsteady fluid forces acting on a disc simulating a human hand were measured in the (sinusoidal) pitching motion. It is confirmed that the pitching motion is available for keeping lift higher after the separation occurs. The delay of stall for the pitching disk is observed and also the value of maximum lift coefficient is greater than the maximum lift coefficient under stationary condition. In addition, the experiments were carried out in the anharmonic periodic pitching motion which has the different pitching rate between the up-stroke and the down-stroke during one cycle. The peaks of the lift and drag curves in the anharmonic pitching motion are shifted against time compared to those in the sinusoidal pitching motion.

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With respect to a viscous micropump using a cylindrical rotor in a rectangular duct, influences of duct height on flow fields and pressure performances are investigated. The model experiment, the numerical simulation and the theoretical analysis are performed. In the model experiment, the low Reynolds number flow is realized by using glycerin as a working fluid for a centimeter-scale (not micrometer scale) pump model. In the numerical simulation, the commercial software, STAR-CD, is used. Qualitative and quantitative agreements between experimental and numerical results are obtained with respect to the flow fields and the performances. With an increase of duct height, the pressure rise at zero flow rate decreases and the flow rate at zero pressure rise increases. In the theoretical analysis, the two-dimensional lubrication theory and three dimensional duct loss are used. The new dimensionless numbers are obtained for flow rate and pressure rise. Theoretical performances show qualitative and quantitative agreements for flow rate and pressure rise. Theoretical performances show qualitative and quantitative agreements with the experimental and numerical ones.

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The flow induced energy-loss of a rotating disk in enclosed fluids bring out significant challenges in the engineering domain of high speed grinding, turbo machinery, circular saws, hard disk, and so on. Since the fluid is supplied continuously to the neighborhood of the disk surface, much of disk's rotational energy is considered to change into kinetic energy of fluid motion. In this study, a control circular cylinder was placed near the disk with its axis of symmetry coincide with that of disk to reduce the supply of flow to the disk. As a result, the fluid torque acting on the disk was found to be reduced significantly when the distance between the disk and the cylinder was intimately small. Furthermore, to measure the fluid torque directly, a new measurement method using load cell was developed in this study.

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The two dimensional numerical method for analyzing a floating device with an Oscillating Water Column (OWC) type wave energy conversion device is introduced where the eigenfunction expansion method is described under the condition that the linear water wave theory is applicable. The method derives the particular solution that satisfies the boundary condition on the water free surface in the air chamber and on the bottom of the floating device. A floating type device is moored on the water surface, which has an Oscillating Water Column on the front side. The floating device captures the wave energy using the heaving, pitching and surging motion of the device and the heaving motion of OWC.

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An existing lifting-line theory for. a non-cavitating hydrofoil in uniform shear flow is applied to both partial- and super- cavitations in the same condition. A lifting-line equation is derived from an assumption holding two-dimensional at any spanwise position and from a solution of ordinary differential equation with variable coefficient. A method in the theory to obtain local cavity length, in which a solution of the lifting-line equation is used, is also applied. The hydrofoil for numerical examples is flat in section, rectangular in planform, and 5 degrees in attack angle. Effects of a main stream shear parameter, aspect ratio and cavitation number on local lift coefficients, total lift coefficients and induced drag coefficients for force characteristics, and on local cavity, length for cavity characteristics are clarified.

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Shell and tube type of heat exchangers are widely used in many applications. Understanding on the cross-flow over tube bundles in a shell is not well established due to the flow complexity and difficulty in measurement, especially in the case of two-phase flow. More detailed and accurate velocity data are needed in order to establish reliable design and optimum performance for tube bundle models. This study was aimed at clarifying the structure of bubbly cross-flow over tube bundles by obtaining detailed velocity data using Particle Image Velocimetry (Hy). Experiments were conducted on two types of model, in-line and staggered tube bundles with pitch-to-diameter ratio of 1.5, containing 20 rows of five 15 mm O.D. tubes in each row. The images of liquid flow and bubbles were distinguished by optical filtering and image processing techniques. The velocities of liquid flow and bubbles were measured successfully and characteristics of the bubbly cross-flow were clarified.

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The uncertainty of mass measurement for the hydrocarbon flow calibration facility, which is a national standard of Japan, has been evaluated experimentally and analytically in detail in accordance with the “ISO Guide to the expression of uncertainty in measurement”. The kerosene and light oil flow calibration rigs have a large weighing tank with a 10 t weighing scale and a small tank with a 1 t weighing scale, one of which is selected to measure the reference flow rate depending on the flow rates. The combined standard uncertainty is estimated to be between 2.7 and 7.7×10^-5s which varies depending on the flowrate and used liquids. The main source of combined uncertainty of mass measurement at high flow rate is the correction factor for weighing scales. On the other hand, uncertainty due to the loss of oil caused by oil mist and vapor in the diverter and in the weighing tank is dominant to the uncertainty of mass measurement using the kerosene 10 t weighing scale and 1 t weighing scales at low flow rate.

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Thermal convection in liquid gallium layer was investigated as a fundamental study for Rayleigh-Bénard convection in low Prandtl number fluid using ultrasonic velocity profiler, UVP. Temperature dependence of sound speed in liquid gallium was measured for a velocity profile measurement by UVP. Measured velocity profiles visualized a convective motion in the liquid gallium layer, and it is a roll shape motion. Spatio-temporal velocity profile showed that there are two types of spatial fluctuation of the convection roll, and there are 3 modes on the number of convection rolls in the fluid layer, 2, 3 or 4 rolls. Two axes-simultaneous velocity profile measurement clarified that expand and contraction of convection roll has a phase delay on the direction of the rotating axis of the roll.

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Theoretical analysis of the frequency response of a fine-wire thermocouple probe was performed. A strict solution of the response was derived and used to investigate influences of the difference in physical properties between two butt-welded thermocouple wires. The solution obtained enables us to understand complex behaviors of the frequency response, even if the physical properties of the two thermocouple wires are greatly different as seen in the copper-constantan (type-T) thermocouple. Additionally, the frequency response at an arbitrary point in the cross-sectional area of the thermocouple wire was investigated. The result shows that a common assumption that the cross-sectional temperature distribution is kept uniform becomes invalid in a high-frequency region, though the nonuniformity can usually have negligible effects on the thermocouple response. The present theoretical analysis provides useful information for revealing the response characteristics of a fine-wire thermocouple probe and for improving the reliability of the fluctuating temperature measurement in high-temperature turbulent flows.

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A new top-heat-type heat transport loop has been constructed. It consists of a heated section, a cooled section, a reservoir, two valves and tubes connecting these components. Water is used as the working fluid. The heat is transported downward from the heated section to the cooled section by utilizing the vapor pressure of the working fluid. This paper explains the principle of operation and describes the fundamental experiments on the heat transport characteristics of the heat transport loop. The experimental results confirm that the temperatures and pressures inside the heat transport loop vary with cycles corresponding to the valve operation, and the heat is transported continuously by the small vapor pressure difference produced inside the heat transport loop. The effects of heat input to the heated section and cooling temperature of the cooled section are also discussed. The good point of this heat transport loop is that its thermal performance is hardly affected by the heat transport height.

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This paper is concerned with the melting of vertical and horizontal ice plates having a 90°corner into a binary aqueous solution inside an insulated rectangular cavity. At the beginning of melting, two vortexes, which are induced from each ice plate, appear in the solution. The velocity is quantitatively measured by particle image velocimetry. The melt water from vertical ice plate effects the melting of horizontal ice plate, and the melting rate is smaller than that of horizontal ice plate only. The numerical results are compared with experimental results, and also predicted the velocity in the liquid melt, melting rate, ice plate temperature quantitatively.

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It is reported that the particulate matter in exhaust gas is reduced when oxygenated agents are added to diesel fuel, but the inhibition mechanisms are not established. To explain this mechanism, we investigates the amount of particulate formation and analyzes thermal cracking and condensation polymerization components with a fluid reaction tube apparatus and nitrogen atmosphere. As a result of experiment, it became clear that inhibition mechanism of fine grain was different by fuel properties.

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Experiments were conducted in order to investigate mixing and combustion processes in a model SCRAM (Supersonic Combustion RAM) jet combustor equipped with a backward-facing step. A detonation-driven shock tunnel was used to generate high-enthalpy flow of Mach number three. Firstly, an influence of installing a sidewall on the combustor model was investigated. Secondly, flow-fields around the step were visualized using high-speed video camera with an aid of schlieren technique. A hydrogen fuel was injected perpendicular to the supersonic flow behind the backward-facing step and a height of the step and an injection distance were varied in order to investigate the effects of these parameters on a characteristic of the combustion. As a result, the injected hydrogen was ignited behind the step and increasing the height of step became effective to the ignition and flame holding behaviors. Furthermore, a non-dimensional injection distance with respect to height of the step was considered to be an important parameter to influence an ignition and combustion processes in the model SCRAM jet combustor.

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A detonation wave produced in a combustible gaseous mixture might cause serious damages by interacting with an artificial structure or human bodies because of an extremely high-pressure and high-temperature behind this wave. Therefore, the detonation wave produced in the gaseous mixture and propagated into a circumstance by accident should be attenuated or quenched within a short distance from its origin. Experiments were conducted in order to investigate behaviors of the detonation wave passing through narrow grooves, since the detonation wave was accompained with a cellular structure and no detonation wave could be propagated. In this study, the detonation wave produced in a gaseous mixture of hydrogen and oxygen was propagated through a grooved block and behaviors of the detonation wave were experimentally investigated by using techniques of pressure measurement and soot track record. As a result, the behavior of detonation wave propagating through the grooved block was classified into two categories, i. e. (i) the detonation wave was quenched, (ii) the detonation wave was once quenched behind the block but re-initiated again by focusing mechanisms of a reflected shock wave on a central axis.

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Flow fields analysis between two channels that were connected with multiple side-channels each other was conducted using lattice Boltzmann method (LBM). We found that calculated flow fields were categorized into three types of flow pattern depending on flow field geometry and flow conditions. The following typical flow patterns are identified : case 1, the incoming flow uniformly passes through the side-channels, case 2, the flow preferentially passes through the side-channel in the inlet and the outlet, case 3, the flow passes through the side-channel of the outlet side. We also found that these flow patterns clearly depend on two dimensionless parameters, ratio of permeability of the side-channels to the channel width and the Reynolds number.

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A new concept of combustion liquid fuel suitable for Gas Turbine combustor was investigated. Combustion in high temperature and low oxgen concentration by Burnt Gas Recirculation (BGR/FGR/EGR) is an important technology for low NO_x combustion of liquid fuel. Upward swirl was focused to produce forced recirculation flow of burnt gas. A combined method of analytical approach (Computational Fluid Dynamics : CFD) and experimental approach was used. Flow pattern produced by the upward swirl introduced into combustion zone from the direction of combustion zone exit was investigated. CFD showed that a kind of guide vanes to produce flow to inside of radial direction at the top of combustion zone had important role for the upward swirl to recirculate fully to the top of combustion zone. A prototype combustor with the design based on results of CFD with and without combustion was made and tested. Non-luminous flame was observed at lean combustion condition. These results showed that this new concept of the primary zone had a high potential as a low NOx combustion technology of liquid fuel.

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Polymer electrolyte fuel cell (PEFC) is a promising candidate for mobile and vehicle applications and distributed power systems due to its high power density and low operation temperature. However, water management in a cathode gas channel is essential for high performance operation of PEFC because oxygen needs to be sufficiently supplied to reaction sites. In this study, we have developed the non-contact measurement technique of water vapor concentration in a gas channel of PEFC using tunable diode laser absorption spectroscopy (TDLAS). Transient profiles of water vapor concentration in an operating PEFC are accurately estimated by this technique and the effects of operating conditions and channel structure on H₂O concentration in a fuel cell channel are clarified.

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Dimethyl ether (DME), which is attracting attention as an alternative fuel for versatile use, has been tried to apply to the Chemically Recuperated Gas Turbine (CRGT), since DME steam-reforming that occurs at temperatures below 350°C with endothermic reaction is suitable for chemical heat recovery and leads to enhancement of power generation efficiency and power output. One of important concerns for the DME-fueled CRGT is related to catalyst reactions in the heat recovery reformer that is a key component of the system because exothermic reactions such as methanation and CO shift disturb the chemical heat recovery. Almost 30 kinds of precious metal-based catalyst were screened using the pressurized reformer to find the most suitable candidate for the CRGT from the viewpoint of LHV increase of the reformed gas. The selected candidate of catalyst was also tested with various temperature, steam/DME molar ratios (S/DME) and pressures. The result indicated that T= 450°C and S/DME = 3.5 was an appropriate condition for the reasons of the balance between endothermic and exothermic reaction rates and carbon deposition. The catalyst was also available for the pressure range up to 2.1 MPa in a MW class GT system without significant decrease of chemical heat recovery.

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