In this paper, we propose a new thechnique for visualizing volume datasets using VRML. In general, a visualization algorithm generates tens thousands of geometric triangles with numerical data, when it is visualized. They are huge in number, if we transfer them through the Internet. To solve the problem, we restrict the visualization on a slice plane and represent triangle mesh as a single quadrateral with a texture image. The texture image are constructed at a server side. We apply the technique to some volume datasets and confirm the effectiveness.

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The flow around a cylindrical body standing on the sand is computed numerically and the movement of the sand is investigated. The numerical method employed in this study can be divided into three parts:(1)calculation of the flow around the pole using MAC method with a generalized coordinate system;(2)estimation of the sand transfer caused by the flow through the friction;(3) determination of the shape of the ground. Since the computational area changes at step(3), this procedure has to be repeated at each time step. Results show that the horseshoe vortex scoops out the ground in front of the pole. When the pole has the plane perpendicular to the flow, it generates a big horseshoe vortex to make the scouring force strong. On the other hand, when the pole has the cross section that is flat along the flow, such as lens or ellipse, the scouring force becomes weak. Furthermore, it is found that the horseshoe vortex becomes small when the pole has the conical base.

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An experiment showed a quite strong effect of inserting a circular cylinder into a unform rising bubbly flow. Size of the dffected zone was more than several times as that of the cylinder. The purpose of present study is to elucidate the mecahnism of generating the two-phase convection using a numerical analysis based on Elulerian-Lagrangian model by which the bubble's bpundary condition on the cylinder can be treated accurately. The numerical results showed a good agreement with the experimental results and revealed the dependency of the flow on the void fraction bubble radius, blockage ratio as well as the bubble's bouncing condition on the cylinder surface.

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It is widely known that two-fluid equations used in most engineering applications do not satisfy the necessary condition for being mathematical well-posed as initial-value problems. In the case of stratified two-phase flows, several researchers have revealed that differential models satisfying the necessary condition are to be derived if the pressure difference between the phases is related to the spatial gradient of the void fraction through the effects of gravity or surface tension. While, in the case of dispersed two-phase flows, no physically reasonable method to derive mathematically well-posed two-fluid model has been proposed. In the present study, particularly focusing on the effect of interfacial pressure terms, we derived the mathematically closed form of the volume-averaged two-fluid model for bubbly two-phase flows. As a result of characteristic analyses, it was shown that the proposed two-fluid equations satisfy the necessary condition of mathematical well-posedness if the void fraction is sufficiently small.

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The vortex method is advantageous to high-Reynolds number flows and its algorithm is relatively simple. However, the number of vortices increases with time and the calculation load of velocties by the Biot-Savart law becomes very large. The authors propesed Lattice Vortex Method (LVM) to accelerate the calculation and to perform numerical analysis stably. The vorticity is not always conserved in the calculation by the conventional finite difference method and the conservation of vorticity is one of the crucial points in numerical flow analysis. In our lattice vortex method (LVM), the vorticity and the density are conserved because those are moved and distributed on cells by Lagrangian scheme. In this paper, lattice cortex method was extended for three-dimensional flow analysis, the vorticities were expressed by vortex rings arranged on the cell sides of the grid to avoid the treatment on the end of vortex lines and Lagrangian scheme was used to preserve the mass and vorticities. The propagation of internal waves was grasped fairly good in three-dimensional stratified flow by LVM.

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Suppression of shock wave/turbulent boundary layer(SW/TBL)interaction occurred inside a supersonic air-intake is important for ensuring and maintaining the aerodynamic performance. It is well known that boundary layer bleed is effective for the SW/TBL interactions and has been employed practically. However, in respect to bleed, there are some shortomings, for example, loss of mass flow rate. In this study, we focused on vortex generators (VGs) that are used as a control device for separation. We calculated a three dimensional SW/TBL interaction field by VGs and investigated the effect of VGs in such a flow field numerically. We researched several configurations of VGs, and found that the largest VGs, which is almost as high as boundary layer thickness, can suppress the SW/TBL interaction in the light of the flow distortion.

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We measured a vortex shedding frequency, gap velocity and the intensity of velocity fluctuation in the fin-tube banks set in a wind tunnel. Two discrete peaks were formed in the spectrum of the velocity fluctuation at the frequencies of 115 Hz and 74 Hz. The vortex shedding phenomena with those frequencies were independent with each other. The peak of 115 Hz mainly formed within the fin-tube banks and the other peak of 74 Hz was in the wake of the fin-tube banks. The applicability of the equivalent diameter obtained by a single circular cylinder with serrated fin to the fin-tube banks was examined. Strouhal numbers were calculated by using the measured values of vortex frequency, gap velocity and the equivalent diameter. Strouhal number in case of 115 Hz agreed well with Strouhal number 0.3 obtained from Fitz-Hugh map for tube banks without fin, and the other Strouhal number in case of 74 Hz was about 0.18 which is similar to vortex shedding from a circular cylinder.

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Reynolds stress tensor for a complex three-dimensional flow field was investigated experimentally in a stronger wall jet managed by two typical kinds of streamwise vortex pair, namely, common -flow up and common-flow down cases. In the turbulent shear flow distorted by secondary flow and strong vorticity, six components of Reynolds stress tensor and rate of strain tensor were obtained with hot-wire measurement. The Reynolds shear stresses <uv> -and <uw> - are reasonably explained with occurrence of corresponding rate of strain-Sxy<=> ∼-(=U/=y)/2and -Sxz <=> ∼-(=U/=z)/2, respectively. The production terms and its global measure integrated in a cross-stream plane show that most of turbulent kinetic energy is produced by - <uv> - =U/=y as well known in many types of two -dimensional flow. In spite of influence by other velocity gradient components, the term -<v²> -=U/=y plays a dominant role on production of Reynolds shear stress component <uv> - through the whole shear layer. It is seen that mean velocity gradient =U/=y is still the most important distortion in such three-dimensional flow field.Difference in increasing rate of streamwise momentum flux between common -flow up and down cases can be related to difference in modification of the mean velocity gradient =U/=y.

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Jets issuing through small holes in a wall into a freestream have proven effective in the control of boundary layer separation. Longitudinal vortices are produced by the interaction between the jets and the freestream. This technique is known as the vortex generator jet method. For the vortex generator jets, the shape and the downstream development of longitudinal vortices are varied by issuing jets discretely (pulsed jets). In order to understand the reasons why the vortices for the steady jet case behave in a manner different from those for the pulsed jet case, velocity measurements were carried out in various phases of pulsed jets. The longitudinal vortices produced by pulsed jets have the stronger influence of a jet pitch angle in comparison with the steady jet case. Pulsed jets promote the interaction between adjacent vortices and therefore the shape and the downstream development of longitudinal vortices are different from the steady jet case.

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The interaction of a straight diffusing vortex tube with a background uniform shear flow is investigated analytically. The vortex tube is aligned with the longitudinal uniform shear flow βye_z and simultaneously the tube undergoes the transverse weak shear αye_χ. In the limit of |α|/β&Lt;1, the asymptotic solution to the Navier-Stokes equation is obtained to examine energy dissipation as well as axial and cross-flow vorticity components around the vortex tube.Vortex lines of the longitudinal shear are wrapped and stretched by the tube to intensify the azimuthal vorticity. This vorticity stretching and intensification are found to be enhanced (or reduced) when the vorticity of the transverse shear is anti-parallel (or parallel) to that of the tube, which leads to the enchancement (or reduction) of the total energy dissipation around the vortex tebu. It is shown that at initial time of evolution βt<0.623(Γ/2πν)^1/3the energy dissipation associated with the tube itself is dominant, while at later time βt>0.623(Γ/2πν)^1/3 the dissipation of the wrapped vortex layers dominates that of the tube, where Γ is the circulation of the tube and ν the kinematic viscosity.

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Measurements in boundary layers with 'moderate'to 'strong'adverse pressure gradients are presented and discussed. With increasing adverse pressure gradients, the velocity profile in U -⁺ ∼ y⁺ coordinates lies below the standard log law, thus indicating a reduction in the thickness of the sublayer. Correspondingly, the turbulence energy components as well as the Reynolds shear stress reduce in the near - wall region of the boundary layer. Waveforms of fluctuating velocity components in the boundary layer, especially in the near-wall region, are remarkably elongated in time in comparison with those in zero-pressure-gradient flows, and thus time scales increase with an increasing pressure gradient parameter P⁺. The increase in time scales is not in proportion to the corresponding increase in the conventional viscous time scale ν/u²_τ. It is found that the Taylor time scale is most appropriate to describe the essential characteristics of non-equilibrium adverse pressure gradient flows. Even the near wall-limiting behavior of streamwise velocity fluctuations for different P⁺ is well correlated in the coordinates based on the Taylor time scale.

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Statistical characteristics of turbulent boundary layer flows subjected to adverse pressure gradients are known to differ significantly from those of zero-pressure -gradient ordinary boundary layers. In this study, the dynamical characteristics of the quasi-coherent structures in adverse pressure gradient flow are investigated experimetally. As the pressure gradient paramenter P⁺ increases, the turbulent energy and shear stress transport <νu²> - and <υuυ> -, in the direction toward the wall from the region away from the wall, become significant in contrast to those in zero-pressure-gradient cases. The quadrant splitting and trajectory analyses reveal the obvious changes do occur in large-amplitude sweep motions(Q4)and outward interactions(Q1). On the other hand, the contribution from other coherent motions, especially the ejection motions(Q2), significantly decrease and their durations become longer, i.e., these motions are dull and less active. Moreover, multi-point simultaneous measurements with five X-probes are made to depict the kinematic pictures of the effects of the adverse pressure gradient on the eddy structures.

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Turbulent structures in the vicinity of a roughness element have been investigated in the boundary layer developed over a k-type rough wall, which consists of two-dimensional bar roughness array with pitch ratio of 4. Measurements were made at a roughness Reynolds number k⁺&eDot;120 in the fully rough regime. In order to discuss role of a separated free shear layer evolving behind trailing edge of a roughness element and vortices formed inside a groove, velocity and length scales were defined with mean and turbulence quantites and wall static pressure measurements.The length scales obtained from the wall static pressure distribution around a roughness element and oil film patterns show that "K-type"and "d-type"are classified with the criterion value of b/k(=groove width/roughness height)=2.5 In the K-type rough wall flow, the length scale is equal to roughness element height. Pressure drag acting on the roughness element in the total wall shear stress is 93% in the k-type rough wall flow, much higher than that of the d-type rough wall flow. Nevertheless, the turbulence velocity and length scales of the separated free shear layer can scale the fraction of pressure drag.

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This paper presents added mass, fluid damping and excitation (negative damping) coefficients for flow-induced vibrations of a shell-type long span gate in which the upstream gate face consists of vertical and inclined skin plates.The equations of motion of the shell-type long-span gate include integral fluid terms which describing the fluid motion in the resorvoir. The fluid terms were calculated for a periodic gate vibration, to reduce to a superposition of the acceleration and velocity terms, thus deriving the added mass, the fluid damping and excitation coefficients in the form of a series summation. The major characteristics of these significant parameters were calculated and examined.Additionaly a fundamental mechanism of the self-excited vibration was described.

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The flow in a thermoacoustic sound wave generator and its application, i. e., power generation with thermoacoustic phenomena, are described. Flow measurement with a hot-wire single probe and simultaneous measurement of velocity, pressure and temperature are performed for analyzing the sound wave generation and propagation mechanism in the resonance tube. Tandem hot-wrie anemometer measurement is employed for ensuring sufficient axial velocity and its direction. Oscillating flow is observed in the resonance tube in which the forward axial velocity amplitude is equal to the backward one. Both forward and backward flow are observed in the central region near the tube outlet where the maximum axial velocity of 43m/s is observed. Intermittent flow is observed far downstream of the resonance tube outlet. Power generation utilizing the flow in the thermoacoustic sound wave generator is successful, where the maximum number of propeller revolutions of 6500 rpm and maximum electric power of 160 mW are obtained.

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Magnetic fluid and MR fluids are representative functional fluids because their properties and characteristics can be controlled easily by applying a magnetic field. Especially, MR fluids has controllable high viscosity, high sensitivity, controllable large yield stress and strong magnetic force in the applied magnetic field due to the robust cluster formation compared with those of magnetic fluid. In the present study, two kinds of nano-MR fluids dispersed iron particle with different diameters are prepared. Vizualization of cluster formation of particles and measurements of physical properties are conducted in the low applied magnetic fields. Finally, damping characteristics of an oscillating flat plate immersed in MR fluids under the low applied magnetic fields are compared with those magnetic fluid.

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A DSMC (direct simulation Monte Carlo) simulation using Dynamic Molecular Collision (DMC) Model based on Molecular Dynamics (MD) calculation is applied for solving a two-dimensional non-equilibrium hypersonic rarefied flow over a flat plate with and without angle of leading edge. Numerical results show that non-equilibrium characteristics between translational and rotational temperature are obtained behind leading edge over the plate. The results of the DSMC agree well with those of the experiments, Howere, the results of the Navier-Stokes are quite different from those of the experiments. The comparison between Larsen-Borgnakke (LB) model and DMC model reveals that the DMC model obtains excellent results without a parameter such as an inelastic parameter.

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When the propagating shock wave reaches at the exit portal of a tube, the impulsive wave discharges to the surrounding area. A new method of passive control that weakens the magnitude of impulsive wave is proposed in this study. An experiment study using a simple shock tube was carried out to examine the effects of a box/helical-vane system at the open-end of a tube. The effect of this system on reduction of the magnitude of impulsive wave is compared with other method of the passive control. The results show that the magnitude of impulsive wave could be significantly reduced by the new method of passive control using the box/helical-vane system. The optimal size of box and helical-vane regarding to decrease of the impulsive wave are determined also.

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A fluid coupling of variable capacity type is able to attain continuous change of rotational speed by changing the fluid capacity, and is widely used as the maximum efficiency amounts to 95∼98%. However, the flow characteristics in the coupling are not well understood, since the liquid and gasco-exit in the coupling chamber, resulting in a very complicated rotating two-phase flow. The present study is aimed to show the flow behavior in a variable capacity type fluid coupling, and the flow was visualized by use of taft method and oil film method and the flow characteristics were determined experimentally. The special interest was focused on the behavior of gas in a rotating chamber and internal flow characteristics. The pressure variation on the runner vane was measured and the change of both transmitted torque ratio and overall performances were discussed.

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A linear analysis of flow instabilities downstream of radial inlet guide vanes is carried out based on the assumption that the flow is two dimensional, imcompressible, inviscid, irrotational upstream of the guide vanes and rotational downstream. An experiment is also made to compare with the results. It is shown that the propagating velocity ratio of flow instability depends on the flow angle and the radius ratio between trading edge of vanes and the outlet of the device. The onset condition of flow instability is discussed. Good agreements between the analytical results and the experimental one reveal that the flow instability mentioned above is basicallyc a two dimensional inviscid phenomenon.

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In order to realize the core flow without using wheels, we experimentally investigate effects of helical ribs caved in a side surface of the capsule. The capsule has 4 ribs of 3mm height or 5mm height. The angle of rib coiling the capsule outer diameter is varied five kinds. The diametrical clearance between the pipe and capsule is 4mm for capsule used. When the capsule mass is small, the capsule velocity is faster then the average water velocity. When an inlet pressure head becomes lower, the capsule of 5mm rib height moves lower than the water flow, although the capsule of 3mm rib height still moves faster than that. When the capsule mass becomes large, the capsule velocity becomes lower than the water flow as well. But the capsule velocity is increased when the angel of rib becomes large. Finally, we observed that the pattern of pressure difference at the popeline is influenced by the capsule surface geometry and the capsule mass.

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Thermophoretic force acting on a particle in a finite space is numerically estimated from the point of view of the position and thermal conductivity of the particle. Simulations are performed by Direct Simulation Monte Carlo Method in which the force is calculated from momentum transports of molecules on the particle surface provided that particle Knudsen number is in the free-molecule region. It is confirmed that the thermophoretic force becomes higher toward lower temperature region in the intermediate region of space Knudsen number 0.01<Kn_H<10. The profiles of the force are nonlinear in the slip region 0.01<Kn_H&lnE;0.1but are linear in the transition region 0.1<Kn_H&lnE;10. The force gradient becomes small as Kn_H increases and the force is almost constant in the free-molecule region. The effect of the particle conductivity on the force becomes larger as Kn_Hincreases but the effect is very small compared with a radiation effect.

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In order to develop a high performance impulse turbine with air flow rectification system for wave power conversion, the impulse turbine has been designed and investigated experimentally by model testing. Then' the running and starting characteristics in irregular ocean waves have been evaluated by a computer simulation, taking account of energy conversion efficiency of oscillating water column. As a result, a suitable choice of design factors has been suggested for the setting angle of guide vane and rotor profile.

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Heat transfer in a rotating square rib-roughened duct was numerically simulated in coordinates fitted to angled ribs. In order to investigate the effect of the Coriolis and buoyancy forces on the turbulent heat transfer disturbed by transverse or angled rib turbulators, the large eddy simulation was adopted with a Lagrangian dynamic subgrid-scale model. For a turbulent Reynolds number of 350, rotating conditions of which the rotation number was 1.0 were computed for rib angles of 90 deg and 60 deg. The Rayleigh number was varied from -5×10⁴ to +5×10⁴;the positive and negative values of the Rayleigh number corresponded to radially outward and inward flows, respectively. The present results clearly showed that the heat transfer was enhanced and suppressed by the aiding and opposing flows induced by the buoyancy, respectively. The friction factor of 60 deg rib was decreased for the increase of the Rayleigh number;on the contrary, the 90 deg rib case gave the increased values.

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The heat transfer characteristics and flow behavior in a rectangular passage with two opposite 45°skewed ribs for turbine rotor blade have been investigated for Reynolds numbers from 7800 to 19000. In this blade, the spanwise coolant passage at the trailing edge region whose thickness is very thin is chosen, so the channel aspect ratio(=width/height of channel)is extremely high, 4.76. Therefore the heat transfer experiment in the high aspect ratio cooling channel was performed using thermochromic liquid crystal and thermocouples. Furthermore the calculation of flow and heat transfer was carried out using CFD analysis code to understand the heat transfer experimental results. The enhanced heat transfer coefficients on the smooth side wall at rib leading end were the same level as those on the rib roughened walls.

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To control the flow around a square prism, a rod was set in upstream of the prism. The side length of the prism was 20 mm and the diameter of the rod changed from 2 to 10 mm. The spacing between the axes of the prism and the rod was 40 to 100 mm, and the Reynolds number ranged from 5.3×10⁴. The relationship between the local heat transfer and the fluid flow around the square prism was investigated. Three flow patterns are occurred. The best flow pattern for enhancement of heat transferand reduction of drag is the pattern without vortex shedding from the rod. The flow pattern changes depending on the rod diameter, its position and Reynolds number. The average heat transfer increase by 35% compared with that of without rod. Further, the reduction of the drag coefficient becomes to about 80%.

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A model experiment was conducted to investigate the dynamic behavior of a liquid sheet under an electric field applied parallel to the flow direction. It was confirmed that the liquid sheet was changed into columns when the applied voltage exceeded a certain critical value. Then a model analysis based on a linear stability theory was carried out to predict the critical applied voltage and it was shown that the analytical results were in good agreemnt with the measured values. Further, based on the above-mentioned model describing the dynamic behavior of the liquid sheet, an analytical model predictiong the EHD effect on condensation heat transfer for a finned tube was presented. It was shown that the predicted results were in good agreement with the experimental data on the flooding angle and condensation heat transfer coefficient for a finned tube under electric fields.

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Experiments were carried out to investigate the flow pattern, average void fraction, and pressure drop of upward air-water two-phase flow in vertical tubes of 25 mm inside diameter with wire coils fo varying wire diameter, pitch and number of coil. Five kinds of flow patterns, i.e., bubble, slug, churn, semi-annular and annular flow, were defined based on the observation of flow behaviors in the experiments. At higher water flow rate, the bubble-slug transition occurred at a lower air flow rate in tubes with wire coil than in the smooth tube. The average void fraction was clarified using the drift flux model. Furthermore, the experimental results of the friction pressure drop were compared with the Lockhart-Martinelli correlation. As a result, a correlation for the constant C in Chisholm's equation was obtained as a function of wire coil pitch-to-diameter ratio.

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An experimental study has been carried out to clarify the characteristics of the void fraction and liquid film thickness of air-water two-phase flow in vertical tubes of 25 mm inside diameter with wire coil of varying wire diameter and pitch. Flow pattern in the experiment of average void fraction and local void fractrion distribution in a cross section is bubble flow, and liquid film thickness is in the region of semi-annular and annular flow. It is clarified from these experiments that the average void fraction in tubes with a wire coil is lower than that of the smooth tube and decreases with the wire diameter owing to the centrifugal force of swirl flow which concentrates bubbles at the center of the tube, and the liquid film thickness between the wire coil is uniformed with the decrease of the pitch of wire coil and that liquid film becomes thicker after the passage of wire coil with the increase of the wire diameter.

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A mumerical approach based on adjoint formulation of convection heat transfer is proposed to predict the change of heat transfer characteristics for arbitrary thermal and flow boundary perturbations. In order to obtain the adjoint system of the convection heat transfer problem, we formally linearize the governing equations by the perturbation method and then derive the adjoint system for the perturbation system. As a result, it is shown that the numerical solutions of the base and the adjoint problems enable us to predict the changes of heat transfer characteristics, such as a change of total heat transfer rate or a change of temperature at a specific location, when the thermal and flow boundary conditions are perturbed. An application example is presented to demonstrate the proposed method.

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The surface tension of molten NaOH was measured by means of the maximum bubble pressure method under the various temperature conditions. The measured value has a maximum at T=723.1 K (T^*), which shows somewhat low temperature compared to that of Nakamura et al⁽10). The two distinct temperature coefficients of surface tension (==σ/=T) with different signs were determined at the lower temperature (T<T^*) and at the higher temperature ranges (T>T^*), but these values are much smaller than those reported by Nakamura et al⁽10). Two dimensional numerical calculations were also conducted to simulate flow patterns due to thermal Marangoni convection formed in a small molten NaOH bridge under the various thermal conditions. By using the measured values of surface tension, the numerical results succeed in reproducing the observed visualiged flow cell patterns, and revealed that the different multi-roll cell flow patterns are distinguishably formed in the bridge depending upon the surface temperature distribution.

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This paper presents the heat transport performance of a Flexible Looped Heat Pipe (FLHP) with the working fluid of ammonium under microgravity condition. The evaporator of the FLHP has two coaxial wicks. The outer wick is made of PTFE with 1.2μm pore diameter and the inner one is made of Polyethylene with 12μm pore diameter. The inside surface of the inner wick is axially grooved. the core of the inner wick is used as liquid reservoir so that reliability of the operation can be enhanced. As the results of the experiment, the FLHP performed normally under microgravity condition and had the predicted capillary limit. the FLHP showed good temperature control ability and was like a VCHP in the range of 150∼240W heat transfer rate. Liquid behavior observed in the visual module assured the normal operation of the second wick and inner axial grooves under microgravity condition.

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We have experimentally evaluated applying the DC arc plasma reactor apparatus to decompose the chlorofluorocarbons(CFCs). The CFC 12 is mixed with Ar gas as a plasma operating fluid and CFC 12 is destroyed in plasma high-temperature atmosphere. In our study, the effects of plasma input power, CFC 12 concentration, plasma temperature and CFC 12 injection method to plasma on CFC 12 decomposition rate have been put into consideration. We found that (i) the maximum decomposition rate of 87% is obtained by (Ar+CFC 12) mixing plasma method, (ii) the decomposition rate of 97% is obtained by using CFC12 direct injection method to plasma jet, and (iii) the decomposition rate is improved by using the reaction pipe installed at the wake of plasma jet. Also discussed is the harmless treatment of by-products in the decomposed gas, as well as the nomination of harmful products associated with practical application.

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Previous results have shown that the plasma-combined with chemical process was effective for the control of NOχ flue gas emissions. However, we could not quantify the reaction byproducts such as N₂O, CO, CO₂, HNO₃ and No₃ -. In the present stdy, two types of the plasma reactors, the ordinary ferroelectric packed-bed plasma reactor and the barrier type packed-bed plasma reactor, were evaluated with regard to reaction products nad NOχ removal efficiency. The ordinary ferroelectric packed-bed plasma reactor showed poor NOχ conversion and produced a large amount of reaction byproducts. On the other hand, the barrier-type packed-bed plasma reactor followed by the chemical reactor showed a superior results : nearly 100% NO χ decomposition with both less than 6ppm of N₂O and CO. The total operating cost becomes $2300/ton, which is at least 1/10 times more economical compared to the conventional NOχ control technologies.

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In order to clarify a breakup mechanism of high-temperature melt jets, a series of experiments was carried out by using a molten tin jet (13 mm in diameter) with initial temperatures from250°C to 950°C. The evolution of large-scale structures, which is caused by organized motion between jet and surrounding fluid, was clearly observed. Local swelling and cavity formation, collapse after swelling, and breakup with ejection and swelling were confirmed in jets with low, middle and high initial temperatures, respectively. These phenomena show that breakup is caused when a high pressure is produced by the fluid entrained inside the jet with enough termal energy due to organized motion.

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Thermal performance of a concrete cool storage unit for a liquid air energy storage system is evaluated. Since the cool storage unit is used in a wide temperature range, a large heat amount can be stored without using latent heat. A concrete composition is investigated for the concrete cool storage unit. This concrete has high durability for low-temperature transients by including air-entraining low-water agent and stainless steel fiber. The major problems for loss of concrete thermal performance are the decrease of concrete thermal conductivity due to crack formation and the decrease of gap conductance due to magnification of the air gap between concrete and heat transfer tube. The decrease of thermal conductivity of the high durability concrete is low, 0.6%/10 cycles which is about 1/7 of normal concrete. The gap conductance does not decrease significantly and its value is about 2.6 times that of normal concrete. Thermal performance of the concrete cool storage unit can be kept after low-temperature transients by using the high durability concrete.

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Temperature sensitive particles have been developed which enable the three-dimensional simultaneous measurement of velocity and temperature in a fluid flow. Even with the recent advances in experimental techniques, the three-dimensional simultaneous measurement of all the three components of velocity and the temperature could not be performed. As for the velocities, one can utilize the three-dimensional particle tracking velocimetry (3-D PTV). But, as for the temperature, even with the laser-induced fluorescence technique (LIF), one can obtain a dense distribution of two-dimensional temperature. Presently, the authors have developed two types of temperature sensitive particles that contain the fluorescence material inside. Using these particles, the simultaneous temperature measurement can be carried out within the framework of the 3-D PTV. In this study, the preparation procedures of these particles have been demonstrated. The calibrations have proved the applicability of the present particles to the temperature measurement and the uncertainties at 20:1 odds are found to be 1.18 degree and 0.78 degree respectively.

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Direct numerical simulations have been performed to clarify the sound generation mechanism in a two-dimensional temporally evolving compressible mixing layers. The sound generation in mixing layer is governed by the variations of vorticity which are induced by the Kelvin-Helmholtz instability. The pressure fluctuations with high frequency are observed in the period of vortex roll-up, and the amplitude of pressure fluctuations increase on the occasion of vortex pairing. The acoustic source term is governed by the Reynolds stress component and the viscous component is negligible. The effects of convective Mach number Mc on sound generation are also investigated. Both the pressure fluctuations and acoustic source term increase with the increase of convective Mach number. For Mc=0.6, shock wave called'eddy shocklet, is produced by the vortex pairing, which dominates the sound generation from the mixing layer at high Mc. The far-field sound computed by DNS is compared with the predictions based on the acoustic analogies derived by Powell and Lighthill. The prediction by Powell's analogy shows a good agreement with DNS, while the pressure fluctuations predicted by Lighthill's analogy are low compared with the DNS results after the vortex pairing.

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Pressure distributions of arrays of In-line blocks on the wall of parallel channel were measured. The square block height and the pitch of the blocks were varied. The effects of the number of line and row and the other factors on the pressure loss were clarified. The pressure drop is divided into three regimes : the inlet, intermidiate and outlet ports of the arrays of blocks. The pressure drop on the inlet port and the pressure rise on the outlet port depend mainly on the function of the opening ratio of the channel and the pressure drop on intermidiate port depends on the blockage ratio, the pitch and numbers of row of the blocks. The pressure loss can be formulated and the recomended equation agrees with the experimental data within ±10%.

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The micro-explosion of emulsified fuel droplets was successfully observed, and the distribution pattern of local frequency of explosion occurrence was estimated in open spray flames of water-in-oil type light oil-water emulsion formed using a twin-fluid (air) atomizer with a ring pilot burner. A schlieren optical system with a deep-cut type knife-edge was adopted for back light illumination, and the process of micro-explosion of each droplet was recorded by a high-speed video camera with an image intensifier. Almost all the patterns of micro-explosion having been observed for single suspended emulsion drops were seen occurring also in the present spray flames. The frequency of micro-explosion occurrence increased as the water fraction in the emulsion was raised or agitation period was elongated. It appears that this frequency increases suddenly from 90 mm above the fuel injection nozzle. It is highly probable, however, that micro-explosion starts somewhere more upstream without being observed due to the difficulty in observation resulted from the excessive density of droplets, since the effect of water addition is most prominent in the upstream region.

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An experimental study has been made of the instantaneous two dimensional visualization of soot distribution profile in a diesel spray flame. The spray flame was formed by a single shot of fuel injection in high pressure and high temperature gaseous environments inside a constant volume combustion chamber. A cross section fo the spray flame was illuminated by a sheet of incident laser light. The images of visible flame and scattered light were recorded simultaneously by using a CCD camera with a gated image intensifier at an arbitrary instant of time after the start of fuel injection. The results showed that the high concentration region of soot existed along the central axis of the spray flame, and that the soot distribution profile was highly heterogeneous. The soot in the spray flame would increase with the lapse of time and would reach a maximum after which it would decrease to a very low value approaching zero. The effects of ambient oxygen concentration, injection pressure and fuel properties on the soot formation were revealed.

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Characteristics of a triple flame generated with methane-air mixture are experimentally investigated in various fuel concentration gradients. The OH radical intensity, which obtained by the direct measurement using an interference filter, and the flame position are measured in each case. The flame position shows that the whole flame width between the both premixed flame wings is wider than the flammability limit width of the unburned mixture. The expanding ratio of this flame width rises by increasing the concentration gradient. The result of OH radical intensity indicates that the most active reaction region is at flame base. The heat value supplied in the flammability limit well explains the behavior at the flame base region. It is also clarified that, at the flame base, the diffusion flame is formed away from the stoichiometric premixed flame, and these flames interact each other.

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Catalytic Combustion is considered to be the best combustion method to achieve lower NOχ levels. And many devices having catalytic combustion have been developed and are under development. For the application under high pressure condition like a gas turbine combustor, a catalyst performance and a catalyst temperature under a high pressure condition must be expected on the data under atmospheric combustion test. The heat and mass transfer effects on a catalytic reaction were studied theoretically, and the results showed good agreement with the experimental results. It is clarified that the mass transfer is dominant in catalytic reaction, the conversion rate is decreased with pressure, and therefore, the catalyst length used under high pressure should be designed longer than that under atmospheric pressure condition.

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The fuel spray distribution in a DI diesel engine with a pilot injection was actively controlled by pilot and main fuel injections at different piston positions to avoid the main fuel injection form hitting the pilot flame. A CFD analysis demonstrated that the movement of the piston with a cavity devided by a central lip along the center of the sidewall effectively separated the cores of the pilot and main fuel sprays. The experiments showed that more smoke was emitted with pilot injection in an ordinary cavity without the central lip while smokeless and low NOχ operation was realized with pilot injection in a cavity divided by a central lip even at heavy loads where ordinary operation without pilot injection emitted smoke so much. The indicated specific energy consumption ISEC was a little bit higher with the pilot injection, mainly because of the reduction in the degree of constant volume combustion. With the advanced pilot injection, ISEC was improved more than that with the retarded pilot injection while the NOχ is a little higher than the retarded pilot injection maintaining still much lower than in ordinary operation.

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To clarify optimal combination of high-pressure injection and exhaust gas recirculaton (EGR) for simultaneous reduction of nitric oxides (NOχ) and particulate (PM) emissions in the diesel engine exhaust, an experimental and theoretical study was performed on a single cylinder test engine. The measured tendencies of NOχ and PM were evaluated in terms of spray characteristics under various injection conditions and of exhaust recirculation rate. The results suggest that the enhancement of air entrainment and turbulent mixing effectively reduce the PM without deterioration of NOχ emission performance at a high exhaust recirculation rate. From an analysis based on a stochastic diesel combustion model, this phenomenon is due to the change in maximum temperature at which the mixture can arrive.

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The mixing of a diesel spray with air is generally determined by the injection parameters and characteristic of the air movement in the combustion chamber. The combustion chamber design can also help to form better mixtures. In this study, improvements in mixture formation was attempted by changing the combustion chamber geometry, injection pressure, and intake gas pressure in an actual diesel engine with transparent cylinder and piston arrangement. With this engine the front view and the side view photographs of the spray impinging on the wall and flowing over the bottom surface of combustion chamber were taken. From these results the overall air and fuel mass distributions were estimated.

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Combustion characteristics and engine performances of a two-stage injection DI diesel engine were experimentally investigated. Two-stage injection was achieved by using two injection pumps. Injection timing and fuel allocation ratio between first and second injection were widely controlled. Engine performance of a two-stage injection diesel engine was compared with that of a single injection diesel engine with early timing injection. The heat release rate was analyzed to understand the combustion phenomena in a two-stage injection diesel engine. As a result, NO emission of two-stage injeciton diesel engine was improved when the first injection timing is early. The various pattern of heat release rate appeared with the change of a fuel allocation ratio. It was greatly affected by the first injection spray impinged on the cylinder wall or the piston top. The trade-off tendency between NO and smoke was influenced by the fuel allocation ratio of sub-injection pump was high.

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Piezoelectric pressure transducer have been used to get an indicator diagram in engine experiments. In these experiments errors, which are caused by miss-setting of TDC mark, integrating coefficient of charge amplifier, thermal distortion fo pressure diaphragm of the transducer and zero drift, make it very difficult to analyze indicator diagram exactly. The authors derived an equation of a pressure drop at inlet and exhaust valves of 4 stroke cycle gasoline engines as a function of engine parameters, with the result of thermal analysis of these drops. This equation enables us to estimate the pressure drop and to compensate zero drift of an indicator diagram.

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The two-fluid cycle is considered for municipal solid waste (MSW) -burned electric power generation, using six kinds of working fluid such as NH₃, C₅H₁2, C₆H₆, and H₂O at the bottoming cycle. The performance characteristics of the two-fluid cycle are obtained at topping steam temperatures of 395 and 495°C. The optimum cycle conditions, which maximize the plant's thermal efficiency, are determined for the respective working fluid. It is shown that the plant's thermal efficiency of the two-fluid cycle was increased to 25.3% from 19.0%, using C₆H₆ as the working fluid under the main steam temperature of 395°C by superheating the bottoming vapor.

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