The sealing performance and the deterrence performance of gas blowout of a sealant self-circulated viscoseal, which is a kind of noncontact seal, are described. Most of the experimentally determined sealing performances are inferior to the theoretical sealing performances, because eccentricity of the circumferential pressure occurs when the viscoseals are horizontal. First, the circumferential and axial pressure distributions are simulated under the assumption that the resultant force generated in sealant is based on not only the pressurized force but also gravity and the centrifugal force. The corrected sealing performance, which is simulated by taking into account the resultant force based on the above named forces are in good agreement with the experimental results. Second, both the gas-liquid interface and the ingested gas motion are seen by observation of naked eye and flow visualization. The regime diagrams of flow in sealant are ensured. Also, it is confirmed that a small amount of self-circulated sealant causes sufficient deterrence of gas blowout in spite of both a high number of screw shaft revolutions and a high cover gas pressure.

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To investigate the influence of the thermodynamic effect on the sub-synchronous rotating cavitation, we conducted experiments in which liquid nitrogen was set at different temperatures (74K, 78K and 83K) with focusing on the fluctuation of the cavity length. Sub-synchronous rotating cavitation appeared at lower cavitation numbers in liquid nitrogen at 74K, which was the same as that in cold water. In contrast, in liquid nitrogen at 83K, the occurrence of sub-synchronous rotating cavitation was suppressed on the increase of thermodynamic effect due to the rising temperature. Furthermore, the unevenness of cavity length under the synchronous rotating cavitation was also decreased by the thermodynamic effect. However, surge mode oscillation occurred simultaneously under the condition of weakened synchronous rotating cavitation. Cavity lengths on the blades oscillated with the same phase maintained the uneven cavity pattern. It was estimated that the thermodynamic effect weakened the peripheral cavitation instability, i.e., synchronous rotating cavitation, but axial cavitation instability, i.e., surge mode oscillation, was induced easily because of the synchronization of the cavity fluctuation with an acoustic resonance in the present inlet-pipe system.

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Rubber products like oil seal are produced by vulcanization molding and the vulcanization molding of rubber product is performed by past experience, trial and error. It is important issues to decrease the product cost, reduce defective products and solve the environmental problems by saving natural resources. If the vulcanization moldings of rubber products are reappeared by computer simulation, it is very useful and it could contribute to solve the above problems. In order to reduce surplus rubber and defective product, numerical analysis of flow phenomena of unvulcanized rubber was performed using commercial software FIDAP. In several types of rubber product models, the analysis was conducted taken the characteristic of visco-elasticity fluid obtained by experiment, without considering the effect of the heat. And experiments were conducted for the comparison of numerical results and actual phenomena. In the experiment, vulcanization process was stopped by arbitrary interval. Then the filling state and the shape of the rubber at each interval are observed in numerical and experiment results. The results showed that the filling state of numerical results represented good agreement with the experimental results. And it was clarified from the numerical analysis that shear stress acted when the unvulcanized rubber flowed in narrow channel and there was the relation between pressure and velocity. In the present paper, the flow phenomena under the condition of the compression molding are shown and the optimum flow conditions are discussed from the numerical results. Furthermore mechanism of occurrence of defective products is considered with the experimental and the numerical results.

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We have investigated aggregate structures of a colloidal dispersion composed of ferromagnetic plate-like particles with a magnetic moment normal to the particle axis at the particle center, by means of three-dimensional Monte Carlo simulations. Such plate-like particles have been modeled as disk-like particles with the side section shape of a spherocylinder. In concrete, we have attempted to clarify the influences of the magnetic field strength, magnetic interactions between particles and volumetric fraction of particles. In order to discuss quantitatively the aggregate structures of clusters, we have focused on the radial distribution and orientational pair correlation function, etc. For no applied magnetic field cases, long column-like clusters are formed as magnetic particle-particle interactions increase. Characteristics of these clusters are that particles incline in a certain direction and their magnetic moments alternate in direction between neighboring particles. For applied magnetic field cases, the particles incline in the magnetic field direction so that the column-like clusters are not formed easily. When the magnetic field has the same order of influence as the magnetic particle-particle interactions, the particles do not form the clusters. However, as the influence of the magnetic field and magnetic particle-particle interactions become significantly strong, thick chain-like clusters are formed along the magnetic field direction.

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To establish a practical method to predict the fluid force on wide variety of particle matters, we propose an efficient model for drag force on string-type agglomerates. The Reynolds number is assumed in the range of Stokes approximation. The immersed-boundary method of body force type developed by the authors is applied for modeling and evaluation of the model. First, model equations to represent drag on basic shapes of two or three spheres are modeled. Considering the characteristics of flow around a sphere at Stokes range, we use cosine formula for the modeling. Then, the model equations are extended to represent the string-type agglomerates of arbitrary numbers of spheres. By testing for the cases of 8 and 16 particles, it is confirmed that our model reasonably reproduces the drag forces obtained by the direct numerical simulation.

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This study proposes a three-dimensional vortex method for bubbly flow. The method discretizes the vorticity field by vortex elements. The behavior of the vortex element and the bubble motion are simultaneously analyzed with the Lagrangian approach. This study also applies the vortex method to simulate a bubble plume. In a tank containing water, small hydrogen bubbles are released from a bubble generator placed on the bottom of the tank. The bubbles rise due to the buoyant force and induce the water flow around them. The simulation highlights that the rising bubbles of the starting plume induce large-scale eddies at the top of them and that the bubbles are entrained into the eddies. It also demonstrates that the large-scale eddies appear around the developed plume and that they cause the meandering behavior of the plume. Such three-dimensional flows are favorably compared with the experimental results, indicating the validity of the proposed vortex method.

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The growth and collapse of a bubble under a floating body are simulated by using the boundary element method with linear elements to predict the damage of ship bodies induced by underwater explosion. The three-dimensional deformation of the bubble, the translation and rotation of the floating body, and the motion of water surface are taken into account in the simulation. It is shown that the bubble deforms three-dimensionally, and the liquid jet threads the bubble due to the interactions among the bubble, the floating body, and the water surface; the directions of the bubble translation and the liquid jet depend on the initial location of the bubble. The Kelvin impulse is found to be useful in evaluating the translational motion of the bubble. Also, the horizontal translational motion of the bubble is much dependent on the rotational motion of a floating body; when the moment of inertia of the floating body is small, the largest horizontal translation is realized between the axis of flotation and the edge of the floating body. It is also shown that there exists an initial horizontal bubble location where the moment of force acting on the floating body has the maximum value.

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A fast simulation method is proposed for underwater explosion. In the method, the motion of a bubble generated by the underwater explosion is modeled with a point source and a doublet; the source and doublet represent the radial motion and translational of the bubble, respectively. The bubble motions are solved coupling with the motions of free surface and a floating body by using the boundary element method (BEM). The growth and collapse of a bubble under a floating body is simulated with the present method. It is shown that the present results are in qualitative agreement with those obtained from the BEM without the bubble model in which the interfacial motion of a bubble is solved directly with the BEM. The present simulation is found to be about six times faster than the BEM simulation without the bubble model.

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This study deals with adaptive response compensation of a second-order system, focusing on a pressure measurement system as a typical example of the second-order system. First, response characteristics of a pressure measurement system were investigated theoretically using three representative mathematical models so far proposed. Although each mathematical model has its own target, the geometric configuration of a pressure measurement system, it is found that there exists a geometric condition in which the frequency response predicted by each model agrees well with one another. Second, where the response of the pressure measurement system can be approximated by the second-order system, the geometric configurations were specified. Finally, the response delay of the pressure measurement system was compensated using the idea of the two-thermocouple probe technique proposed by Tagawa-Ohta (1997). As a result, the governing parameters of the response characteristics of the pressure measurement system were estimated successfully. The results show that the present technique can be generally applicable to the response compensation of various sensors and measurement systems whose response can be represented by the second-order system.

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It is known that the interface current exists besides the bulk current in the channel of the electroosmotic flow (EOF). Interface current in electric double layer (EDL) is a main driving force of the EOF. However, due to its small size and the various geometrical constraint to access EDL, it is difficult to measure the interface current experimentally. In this study, a specially designed doughnut channel is utilized to measure the interface current. Two parallel doughnut-shaped glass plates were used for the doughnut channel. It is possible to adjust the height of doughnut channel continuously. Experimental studies were carried out on fully developed steady EOF in this channel. The characteristics of the interface current were examined. It is the first time that the interface current in a EOF was measured directly by experimental method. The structure of the EOF or EDL was considered in relation to the interface current.

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The causes of disagreement between a priori and in situ results of Pressure-Sensitive Paint (PSP) measurements in cryogenic wind tunnels have been investigated. Systematic experiments were conducted in the JAXA 0.1-m cryogenic wind tunnel to clarify the factors of the disagreement. In the experiments, the influence of total and static temperatures, and oxygen concentrations in the cryogenic wind tunnel on PSP results were evaluated. Consequently, it was detected that this disagreement originates in the difference between a total pressure-change calibration and a partial oxygen pressure-change calibration, and the hysteresis of luminescent intensity during pressurization and depressurization process at low temperatures less than 110K.

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A boundary layer transition on a 10-degree cone model in a supersonic flow was visualized by means of a temperature-sensitive paint (TSP). A transition front can be detected as the edge of brightness measuring the temperature difference between laminar and turbulent boundary layers. To enhance a thermal signature across the transition line, a sudden temperature step is introduced into the wind tunnel and global transition patterns on the cone model were clearly visualized. In this study, a quiet test region in the test section was visualized first. Then, the effects of Mach numbers, Reynolds numbers and angles of attack on the transition patterns were studied with emphasis on transition caused by crossflow instability.

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This paper presents results of an experimental study on pressure fluctuation occurring at the inside of narrow slots beneath turbulent boundary layers. Experiments were carried out at a Reynolds number range of 3×10^4<Re_θ<1.25×10^5 using a large re-circulating water tunnel. Fluctuating pressure was measured for three types of slots; two spanwise slots of 1mm and 3mm width and a streamwise slot of 1mm width. In case of spanwise slots, measured pressure spectra show 4-6dB lower values than those measured on smooth surface. However, obtained two-point cross-spectral densities reveal that pressure fluctuations at the inside of the spanwise slot are more coherent than those measured on smooth surface. In case of streamwise slot, pressure fluctuation levels increase remarkably at a low frequency range.

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This paper describes an experimental study of the flow past a tapered circular cylinder placed on a ground plane. The experiment was carried out in an N.P.L. blow down type wind-tunnel having a working section of 400mm×400mm×2000mm in size at the Reynolds number 1.29×10^4 and 3.87×10^4. The surface-pressure distribution on tapered cylinder of taper ratio of t=0, 0.05, 0.10, 0.143 (H/D=7) and t=0, 0.385, 0.769, 1.154 (H/D=0.87), and around the tapered cylinder on the ground plane were measured. The drag and lift coefficients were determined by integration of the surface pressure. The vortices of two kinds generated in the flowfield around a tapered cylinder have also been observed by the flow visualization. Consequently it is found that the Karman vortices and arch vortices were shed from the tapered cylinder and circular cone of vertex angle 2α=8°(H/D=7), and from the tapered cyliner and circular cone of vertex angle 2α=60°(H/D=0.87) respectively.

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LDV measurement and flow visualization have been made in order to investigate the behavior of horseshoe vortex and flow separation around a cone mounted on a plate. The apex angle 2α of cone is less than or equal to 90° and the height is 50mm. The Reynolds number based on the height is 1100, and the relative boundary layer thickness is 0.41. The streamwise positions of boundary layer separation and primary horseshoe vortex measured from the upstream bottom edge of the cone are proportional to the height of the front stagnation point. The strength of the spanwise mean vorticity of the primary horseshoe vortex depends on the boundary layer mean vorticity distribution. The reverse region formed behind the cone enlarges with the bottom diameter. The configuration of the reverse region depends on both the Reynolds number based on the velocity scale of the pressure acting on the upstream surface of the cone and the strength of spanwise additional strain rate induced by the primary horseshoe vortex.

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A novel measuring method for dynamic surface tension of surfactant aqueous solutions is proposed. In this method, the dynamic surface tension is measured by comparing the trajectory of a free laminar liquid jet ejected horizontally from a circular orifice to a theoretical trajectory. The theoretical trajectory is obtained by solving ordinary differential equations, which is conducted from momentum balances between inertial force, surface tension, gravitational force and pressure. Circular cross section and simplified pressure distribution in the liquid jet are assumed in the theoretical analysis. Surface tension affects the trajectory of the horizontal jet with inertial force and gravitational force under the condition of Weber number We&ap;1 and Bond number Bo&ap;1, whereas viscous force is negligible because the order of capillary number is 10^<-3> under the experimental condition of this study. The experimental trajectory is obtained by photography. The experimental trajectory is compared with a theoretical trajectory calculated at an assumed surface tension, and the theoretical trajectory in agreement with the experimental trajectory gives the time varying surface tension (dynamic surface tension) of liquid. The obtained dynamic surface tensions of several kinds of surfactant aqueous solutions by this method agree well with ones measured by conventional oscillating jet method and maximum bubble pressure method. This agreement proves the validity of this method.

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Applying micro spray of electrostatic inkjet to thick film coating was examined experimentally. High quality coating is expected by drops-on-drops of super fine and mono-diameter droplets. At first, the jetting states of two viscous solutions were observed to determine coating parameters. Then, with those parameters examined, the possibility of thick film coating was tested. According to the increment of applied voltage, jetting mode was varied from Mode 1, dripping, to Mode 2, jetting. The most favorable condition for coating was the stable cone-jet mode in the jetting mode, where a well-oriented thread was jetted from the stable Taylor Cone at the nozzle tip and broken up into mist during flight. From the coating experiments with the selected liquid and conditions of jetting, the possibility of uniform and thick film was demonstrated by piling up the droplets several times, whose diameters were less than 10 micrometers. The alternative methods to enhance breaking up of droplets and stabilize its process were also proposed.

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Nucleate boiling heat transfer coefficients of ammonia/water mixtures have been measured when a surface-active agent was added into the mixtures. The experiment has been carried out on a horizontal heated fine wire at pressure of 0.4MPa. The effect of the concentration of the ammonia and the surface-active agent on the coefficients was experimentally clarified in the ammonia fraction of C=0.3 and 0.7 and in the surfactant concentration of C_s=0-3500ppm. As a result, the coefficients were enhanced in lower ammonia fraction, C=0.3 and in low heat flux, which is just after onset of boiling. It was also found that the enhancement effect by the surface-active agent disappeared in surfactant concentration over 1000ppm in C=0.3. It is also shown that the heat of mixing generated near vapor-liquid interface can be easily removed and pressure and temperature in the system can be easily controlled by placing a cooling pipe on vapor-liquid interface and that measurement accuracy of the heat transfer coefficients is improved. We correlated using the improved measurement data in the current paper.

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In order to elucidate the mechanism of low thermal conductivity caused by nanostructures and nano-structural clearances, we calculated thermal conductivity, phonon dispersion relationships, and density of states in argon and diamond thin film systems depending on nanostructures and nano-structural distances by the classical molecular dynamics simulation. We can observe some change of the group velocity of phonon in the dispersion relations of the longitudinal wave as well as the reduction of thermal conductivity when the nano-structural distance was relatively small. However, the change of the phonon dispersion relations and the density of states are not so large in the systems with nanostructures in comparison with the perfect lattice systems.

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The baroclinic torque, which is generated by density gradient and pressure gradient, is studied with a PIV (Particle Image Velocimetry) method. In this work, the two dimensional density gradient is formed in binary density planar boundary stratified by the gravity. The pressure gradient is introduced with penetration of a pair of two dimensional vortices into the density boundary. A series of the experiments is carried out in micro-gravity field so as to allow buoyancy-free condition. The results show that the baroclinic torque is induced on the boundary of binary density field by approaching the pair vortex to the boundary. This result indicates the possibility of numerical analysis where the baroclinic torque is introduced precisely by the discrete vortex method as one of Lagrange method at inhomogeneous density flow field.

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The mass transfer characteristics of gas diffusion layer (GDL) are closely related to cell performance in PEFC. In this study, the configuration of new type GDL, in which two kinds of porous media having different wettability are arranged alternately (Hybrid type GDL), was proposed. The characteristics of oxygen diffusivity with respect to its water content (saturation) were measured by using an experimental apparatus consists of Galvanic battery type oxygen sensor as an oxygen absorber. Experimental results show that the Hybrid stucture has great advantages compared to conventional GDL with single porous material.

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Effect of motion of atoms or molecules on dissociation probability was analyzed by Molecular Dynamics (MD) Method. Platinum (111) surface and hydrogen were chosen to be the metal surface and the gas molecule, respectively. In the 1st report, an Embedded Atom Method was improved to reproduce characteristics of each site of Pt (111) surface. The results show that these values obtained by DFT calculation can be reproduced by the improved EAM potential and the validity of the potential was verified. In this 2nd report, a dissociation probability at each site was obtained by MD method against impinging energy. On the other hand, the same dissociation probability was also obtained by the dissociation barrier at each site and orientation of a hydrogen molecule. These results are compared with each other and the effect of motion of atoms or molecules on dissociation probability was analysed. Consequently, the dynamic effects on dissociation probability are remarkable at top site while they are not at brg or fcc site.

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To clarify the mechanism of coupling phenomena such as heat, mass and electric charge transfer in a single-cell polymer electrolyte fuel cell (PEFC), we have measured in-plane temperature distribution in a single-cell PEFC by thermograph under power generation. We have investigated the influence of gas flow rate at inlet and gas channel pitch of separator on in-plane temperature distribution and power generation performance. As a result, the higher temperature region is observed near the outlet of cell when the stoichiometric ratio of gas flow rate is set over 1.00 due to the convection heat transfer by excess oxygen flow in gas channel at the cathode. When the stoichiometric ratio of gas flow rate is set at 1.00, in-plane temperature distribution becomes uniform and high power generation performance is obtained. Total voltage is increased and temperature in observation area is decreased with decreasing the gas channel pitch of separator irrespective of gas flow rate.

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Operating range of HCCI engines is limited by an excessive pressure rise rate (PRR) in high load region resulting in engine knock. Dispersing auto-ignition timing at each local area in the combustion chamber and retarding combustion phasing (CA50) are main methods of decreasing the excessive PRR. Changing mixing ratio of two fuels which have different auto-ignition characteristics leads to the change of combustion phasing. The objective of this study was to investigate the effect of making the variation of mixing ratio in the mixture to change the combustion phasing at each local area in the combustion chamber on reducing PRR. The test fuels were DME and n=Butane which both have LTHR and HTHR during HCCI combustion. In addition to in-cylinder gas pressure measurement, in order to assess the combustion at each local area, chemiluminescence imaging and numerical analysis with multi-zones modeling were used. Maximum PRR changes depending on mixing condition of DME and n-Butane. When DME is stratified and n-Butane is distributed uniformly in the combustion chamber (Case 3), maximum PRR becomes lowest. In Case 3, the appearance timing of chemiluminescence at each local area is dispersed and the duration of chemiluminescence is longer than in Case 1 (DME and n-Butane are both distributed uniformly). By numerical analysis, it is found that the temperature distribution and difference of HTHR start temperature makes difference of HTHR start timing in each zone.

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In this paper, as a new application of Stirling cycle, it is proposed to apply the Stirling cycle to heat speaker which amplifies sound vibration by means of the thermal energy. The heat speaker is composed of a pressure vessel whose capacity is variable, a displacer to which a voice coil is attached, a vibration board attached to the pressure vessel and a permanent magnet placed around the vessel. The displacer with voice coil is vibrated by the magnetic force which is generated by electric current of sound signal flowing in the voice coil. The vibrating displacer makes the air come and go between the hot side and the cold side in the pressure vessel. The air temperature goes up and down, and then the pressure follows it. The capacity of the vessel repeats expansion and shrinkage by the pressure change of the air. The moving vessel vibrates the vibration board and it yields the sound.

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