The purpose of this paper is to construct and develop the Moving Embedded-Grid method for simulation of three-dimensional incompressible flows including obstacles traveling long distance. The feature of the presented method is that the Embedded-Grid can move without restriction in all directions in a stationary main grid covering the whole of the flow field. The method is constructed based on the four-dimensional control volume in space-time unified domain such that the method assures to be divergence-free in the space-time unified domain and thus satisfies both the physical and geometrical conservation laws simultaneously. First of all, it is confirmed that the present method satisfies the geometric conservation law. Next, the method has been applied to the flow around a sphere traveling long distance in a stationary fluid and the result shows good agreement with other reference solution. The method has been applied to the flow in a mixer in order to investigate the effective scheme of stirring two fluids by rods and the unsteady behavior of the flow is shown. The results show the promising feature of the method.

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Turbulence characteristics in the spatially developing fractal-generated turbulence are investigated by means of the direct numerical simulation (DNS). Three kinds of fractal grids, namely, cross, I and square types, are numerically constructed using the immersed boundary method. The results show that fractal grids generate high turbulence intensities compared with the classical grid turbulence using a biplane square mesh grid at the same mesh Reynolds number. Among the three types, the fractal square grid is the best to generate nearly homogeneous and isotropic turbulence in the far downstream decaying region. The integral length scale in the fractal generated turbulence remains approximately constant in the decaying region, whereas it grows downstream in the classical grid turbulence. These results are in good agreement with the previous experiments.

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An experimental study is performed for turbulent channel flow over an inclined backward-facing step. The Reynolds number based on the mean velocity at the inlet and the step height ranges from 1.0×10^4 to 4.0×10^4, and the inclination angle of the step is changed to 30゜, 45゜, 60゜ and 90゜. The expansion ratio of the channel is 2.0. The wall static pressure and local heat transfer coefficient are measured behind the inclined backward-facing step. To investigate the relationship between fluid flow and heat transfer characteristics, the velocity profiles and turbulent quantities are measured by PIV. It was found that the pressure drop at the step was reduced and the heat transfer coefficient in the recirculating region was improved by tilting the backward-facing step. When the inclination angle was 30゜, the highest heat transfer coefficient was obtained. Enhancement of the heat transfer coefficient was related to the increase of turbulent energy, Reynolds shear stress and turbulent diffusions.

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Present study revealed that the mean and the turbulent characteristics of the flow fields where edge tone phenomenon is suppressed by the interaction of square bars approach two dimensional jet. It was also revealed that the suppression of production terms is the main cause of the phenomenon that out of the turbulent characteristics, streamwise turbulent intensity <u_1^2>^^^- and Reynolds stress -<u_1u_2>^^^- decrease and approach to the value of the two dimensional jet. On the other hand, the results of non-isotropy tensor of velocity b_<12> and the production term of <u_2^2>^^^- component imply that the decrease in vertical turbulent intensity <u_2^2>^^^- is caused by the suppression of redistribution term, more specifically, the energy transfer from <u_1^2>^^^- to <u_2^2>^^^-. Besides, the comparison result of the phase-averaged non-isotropy tensor of velocity <b_<12>> and the vortical structures induced by edge tone phenomenon implies that the energy transfer from <u_1^2>^^^- to <u_2^2>^^^- is generated at the positive pressure regions, and the control of the vortical structures suppresses the energy transfer from <u_1^2>^^^- to <u_2^2>^^^-.

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Hot water in main pipe flows into the branch pipe and form thermally stratified layer with cold water at the bent section. Velocity fluctuation of the downward vortex may cause swaying of the layer. To investigate its impact on pipe wall temperature fluctuation, wall temperature distributions at the bent section were obtained experimentally for various main flow velocities. These experiments revealed that, (1) wall temperature fluctuation was attenuated significantly by heat transfer but it was also observed above and below the thermally stratified layer due to heat conductance through the wall; (2) the area of significant wall temperature fluctuation distributed horizontally for main flow velocity of 6 and 7m/s and it distributed in a block at extrados of the bent section for main flow velocity of 10-13m/s; (3) the maximum wall temperature fluctuation was 0.25 of main to branch fluid temperature difference; (4) the major peak of wall temperature fluctuation was observed within the range of 0.0015-0.0068Hz for main flow velocity of 6, 11 and 13m/s.

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A theoretical and experimental consideration is conducted to propose a novel method to measure the dynamic surface tension of surfactant solution. The trajectory of laminar jet injected from a horizontal capillary tube is considered from an approximate theory. The momentum balance is discussed between surface tension, gravitational force, pressure and viscous force. Since the effect of gravitational force is relatively small compared with the surface tension, the cross section of jet is assumed as a circle and the pressure inside the jet is approximately obtained from the Laplace equation. The ordinary differential equation of motion is solved numerically by the simple Runge Kutta's method to obtain the profile of jet trajectory. The trajectory profiles are measured experimentally for water and two kinds of ethanol solutions with smaller surface tension than that of water. The theoretical profiles agree well with experimental ones for each condition and the trajectories are strongly dependent on the surface tension. It is demonstrated that the change of surface tension of surfactant solution could be measured by the method proposed in this study.

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In the present paper the attention is focused on the vortex shedding from the tube banks with closely mounted twist serrated fin. The tube banks were installed rigidly in the test section of the wind tunnel. We measured the mean velocity, the spectrum of velocity fluctuation and the gap velocity in the simulated tube banks which has same pitch ratio as that of a boiler heat exchanger, We found two types of vortex shedding with different Strouhal number of 0.40 and 0.20 in the case of Reynolds number R_e, based on the equivalent diameter and gap velocity, between 2.8×10^4 and 6.2×10^4. Strouhal numbers S_t were calculated by using the measured values of vortex shedding frequency, gap velocity and the equivalent diameter. The vortex shedding of S_t=0.40 mainly formed within the fin-tube banks and the other vortex of S_t=0.20 was in the wake of the fin-tube banks. Strouhal number of vortex shedding inside the fin-tube banks changed from 0.40 to 0.32 over R_e=6.2×10^4. The applicability of the equivalent diameter obtained by a single circular cylinder with serrated fin to the fin-tube banks was examined. Strouhal number 0.32 agreed with Strouhal number 0.30 obtained from Fitz-hugh's map for bare tube banks and other Strouhal number of 0.20 is similar to the vortex shedding from a circular cylinder.

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We propose experimental evaluation methods for dipole sound based on the vortex sound theory. By using time-resolved PIV in a wind tunnel test, we measured time series data of the unsteady two-dimensional flow around a circular cylinder which is suitable for applying the theory and validating the methods. The sound pressure in a far field estimated experimentally from PIV measurement is validated through comparison with correlation analysis with the measured sound pressure. Furthermore, we performed a correlation analysis between the source intensity defined as the integrand in the equation of the vortex sound theory and the measured sound pressure to clarify the relationship between the estimated dipole sound and measured flow field. As a result, it is shown that the estimated sound pressure can detect the Aeolian tone due to the Karman vortex shedding. Periodic fluctuation around the shear layer separation regions and the vortex formation region in the wake causes the estimated dipole sound.

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Turbulence modification by dispersed bubbles in an upward pipe flow was investigated by particle tracking velocimetry and bubble shape projection imaging. Time duration of CMOS camera frames was much smaller than the Kolmogorov time scale, so that measurments with a high time resolution were achieved to resolve the dissipation process of turbulence in the presence of bubbles. Two different bubble diameters at the void fraction up to 1.5% were examined. The profiles of mean streamwise velocity of water were flattened in the pipe middle region, because the bubbles accumulating near the pipe wall accelerated the fluid. The flattened mean flow profiles suppressed the shear-induced turbulence intensities. The dissipative eddies around small bubbles, whose size is approximately five times the mean diameter of small bubbles, increased the dissipation rate of turbulence kinetic energy. On the other hand, the turbulence intensities were augmented by the interactions between the eddies generated by the large bubble and the shear-induced turbulence amongst large bubbles, which resulted in the significant enhancement of dissipation process of turbulence kinetic energy.

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A thermal problem and the Couette flow of a rarefied argon gas between two platinum walls are considered to investigate the characteristics of the reflected gas molecule at a physically adsorbed surface by H_2O molecules. The analysis is based on the molecular dynamics (MD) method for the interaction of gas molecules with the adsorbed wall surface together with the direct simulation Monte-Carlo (DSMC) method for the motion of gas molecules. The accommodation coefficients of momentum and translational energy of the molecule are obtained. The temperature and flow velocity distribution between two walls and the distribution function of the reflected molecule are also obtained. It is found that the tangential momentum accommodation coefficient of the adsorbed surface is much larger than that of a clean surface. The Maxwell-type distribution function consisting of specular and diffuse reflection well describes the distribution function of the reflected molecules if the accommodation coefficient involved is chosen properly.

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A new technique of hydrogen and carbon monoxide production from solid carbon using microwave was developed. By dielectric heat effects due to the irradiation of microwave, the solid carbon is heated to above 1000℃. Under the conditions, it is expected that the solid carbon reacts with steam, and produces hydrogen and carbon monoxide. To confirm this concept, a fundamental test was performed. As a result, hydrogen and carbon monoxide production rate was proportional to the power of microwave and was influenced by heat loss to the exvironment.

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Numerical and experimental studies on forced and mixed convection heat transfer and freezing for low Reynolds numbers in a vertical duct with asymmetric side-wall cooling at a subzero temperature have been conducted. Numerical results on the ice-layer thickness at steady state were compared with experimental measurements, and a qualitative agreement was observed. It is found that, after the cooling is initiated, a new velocity profile of the main stream, which is formed under the influence of buoyancy, develops in a short time. As the ice-layer grows thicker, however, the parabolic velocity profile is recovered again. The experimental measurements are also in fair agreement with the analytical predictions based on Graetz theory. However, in the experiment, the super cooling always takes place over the entire cooling surface, and it delays the ice formation significantly. The same super cooling was observed at high Reynolds numbers. Consequently, in the growth limit of solidification, the average thickness of ice-layer is found to be proportional to about -1/3 power of the Reynolds number.

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The cooling capability in compact electronic equipment in natural convective flow fields has been investigated. The relationship between clearance of a channel and natural cooling capability was obtained. Temperature and velocity measurements were carried out using a channel model of electronic equipment having a vertical duct of rectangular section. The channel model was constructed with two copper walls and two transparent acrylic walls. The clearance between the copper walls was used as a parameter for the channel model. Velocity profiles of natural cooling flow in the channel were quantitatively measured using particle image velocimetry (PIV). The temperature and velocity results demonstrated that changes in the velocity profiles and temperature profiles closely depend on the wall clearances. The clearance from 8mm to 10mm is the best size for the natural cooling capability in the channel in this study.

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Two rectangular block-like elements as an electronic module are positioned in a parallel-walled channel and cooled by forced convection airflow. A metal plate with holes as a barrier protrudes above the plane of the modules, which is intended to function as a cover for protecting them from mechanical or electromagnetic damage, or as a thermal control device. Per-module heat transfer coefficients in the presence of the barrier of various height, H, and distance, L, between the module and the barrier were measured. In the presence of the barrier with holes, the heat transfer coefficient at two modules is rapidly diminished. Nusselt numbers are correlated as a function of Reynolds number and H/L.

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By using a flow calorimeter, the speific isobaric heat capacity (c_p) was measured for R 134a (1,1,1,2-tetrafluoroethane) in the gas phase. Seven measurements for R 134a were obtained at temperatures from 323 to 343K and at pressures from 1.0 to 1.8MPa. Some of them are close to the saturation curve. The expanded uncertainty (k=2) of the temperature measurements is estimated to be less than 18mK, and that of the pressure measurements is less than 6.6kPa. The expanded uncertainty for c_p is estimated to range from 13 to 26J・kg^<-1>・K^<-1>. Also, five measurements for carbon dioxide were obtained from 315 to 333K and from 2.0 to 2.5MPa by a modification of the apparatus. The expanded uncertainty (k=2) of the temperature measurements is estimated to be less than 87mK, and that of the pressure measurements is less than 16kPa. The expanded uncertainty for c_p is estimated to range from 45 to 63J・kg^<-1>・K^<-1>. The experimental data of R 134a and carbon dioxide were discussed in terms of available equations of state.

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Partial dehydration by microwave-vacuum drying has been applied to mackerels in order to reduce cell-damages caused by the formation of large ice-crystals during freezing. The samples were subjected to microwave vacuum drying at pressure of 5kPa and temperature less than 27℃ to remove small amount of the water prior to freezing. The mackerels were cooled by using the freezing chamber at temperature of -20℃ and -80℃, respectively. The observations of ice crystal clearly indicated that large ice crystals were mainly formed in the intercellular spaces when the mackerel was frozen at the both cooling conditions. It is also can be understood that the formation of large ice crystals has a close relation to the cell damages. In this experiment we successfully confirmed that rapid cooling and pre-dehydration are effective in minimizing the size of ice crystal. After thawing, the pre-dehydrated samples showed a less drip loss than the un-dehydrated one. It is considered that the pre-dehydration by microwave-vacuum drying is one of promising method for the cryo-preservation of foods.

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A theoretical and experimental study is conducted to investigate the detached volume from the pendant drop on sphere surface. From the observation of droplet detachment by use of a high speed video camera, the movement of upper part from the neck of droplet is quite slow compared with that of detaching lower part. The surface profile of upper part was calculated approximately as a static problem by using the axi-symmetric Laplace equation. Using the droplet profile, the system energy was calculated including the work done by the solid-liquid wetting behavior. Based on the condition of energy minimum, the volume of upper part was determined among the solutions satisfying the boundary conditions and the volume of detached part V was calculated. The volume V increases with the sphere diameter and approaches to that for the plate. V is strongly dependent on the wettability between sphere and liquid, and decreases with the receding contact angle. The detached volume of water droplet was measured for spheres of porous brick with various diameters. The results agreed well with theoretical ones obtained in this study.

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A separate analysis of the anode and cathode impedances of a practical solid oxide fuel cell (SOFC) has been performed. Electrochemical impedance spectroscopy is used for the analysis of a micro tubular SOFC havig anode-supported electrolyte with two-electrode set-up. This cell is composed of an Ni/(ZrO_2)_<0.9>(Y_2O_3)_<0.1> cermet anode, an La_<0.8>Sr_<0.2>Ga_<0.8>Mg_<0.2>O_<2.8> electrolyte, and an La_<0.6>Sr_<0.4>(Co_<0.2>Fe_<0.8>)O_3 cathode. Measurements are carried out for the cell operated at 700℃ with varying flow rate and composition of H_2-N_2 mixture gas fed into the anode and those of air-O_2 mixture gas fed into the cathode. The anode and cathode impedances are thereby found to appear in low and high frequency regions, respectively. A common equivalent circuit model is applied for the complex nonlinear least squares curve fitting of impedance spectra to acquire the resistances and capacitances of the charge and mass transfers at the anode and cathode, and the cell Ohmic resistance. Then variation of those parameters of the equivalent circuit in accordance with anode gas feed conditions are obtained for the practical SOFC. They are useful parameters for health diagnosis of SOFCs.

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The present paper addresses a separate overpotential analysis of the anode and cathode of a practical solid oxide fuel cell (SOFC). Electrochemical impedance spectroscopy with two-electrode set-up is used for the analysis of a micro tubular SOFC having anode-supported electrolyte. This cell is composed of an Ni/(ZrO_2)_<0.9>(Y_2O_3)_<0.1> cermet anode, an La_<0.8>Sr_<0.2>Ga_<0.8>Mg_<0.2>O_<2.8> electrolyte, and an La_<0.6>Sr_<0.4>(Co_<0.2>Fe_<0.8>)O_3 cathode. Measurements are carried out for the cell operated at 700℃ with varying flow rate and composition of H_2-N_2 mixture gas fed in the anode. In our previous study, the anode and cathode impedances have been found to appear in low and high frequency regions, respectively. Therein, the Ohmic resistance, and the charge and mass transfer resistances at the anode and cathode were evaluated. In the present study, the Ohmic, activation and concnetration overpotentials are then evaluated by integration of those resistances. The anode and cathode activation overpotentials are found to be separated using the Butler-Volmer equation. Thereby the concentration overpotential of the anode is also found to be separated by subtracting the anode activation overpotential from the anode overpotential, while the cathode concentration overpotential is found to be negligible. The separation of the overpotentials is successfully confirmed by the observation of the variation of the overpotentials in conjunction with the variation of the anode gas flow rate and composition, giving the exchange current densities. The analysis shows that decreases in the anode activation overpotential and concentration overpotential including the Nernst loss imporove the cell performance.

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Gas diffusion layers (GDLs) coated with a microporous layer (MPL) have been commonly used to improve water management properties of polymer electrolyte fuel cells (PEFCs). However, the appropriate pore diameter, thickness and hydrophobicity of the MPL remain unclear. In the present study, the influences of MPL design parameters on permeability and PEFC performance were evaluated. A decrease in the pore diameter of the MPL reduces through-plane permeability significantly, but reduces in-plane permeability only slightly. Under high-humidity conditions, a decrease in the MPL pore diameter is effective for preventing flooding, enhancing the PEFC performance. However, when the pore diameter becomes too small, the PEFC performance tends to decrease. Reducing the MPL thickness improves in-plane permeability, enhancing the ability of the MPL to avoid flooding. Under low-humidity conditions, a decrease in the MPL pore diameter is effective for preventing drying-out of the MEA. Increasing the MPL thickness is also effective for maintaining the humidity of the MEA. However, when the MPL thickness becomes too large, the transport of oxygen to the electrode through the GDL is deteriorated, lowering the PEFC performance.

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Flame is affected by external electric field because it contains ions and electrons related to chemical reaction. On the other hand, movement of ions and electrons affects external electric field due to their charge. Since there are a few studies to discuss the change of external electric field, this paper discusses the change of electric field from the experimental results with different electrode distance. It is supposed from 1-D steady-state analysis that if electric field is changed spatially the effect of electric field on combustion behavior is aligned with V^2/L^3 where V is applied voltage between electrodes and L is distance between the electrodes. Because flame deforms to cathode due to electric body force in electric field, the change of flame shape of burning ethanol droplet is observed in vertical DC electric field and electric current during combustion is measured. The result shows there exists the applied electric voltage where flame becomes vertically symmetry to balance the buoyancy by the electric body force and relation between m and n of V^m/L^n for flame symmetry is n/m=1.5. Depending on this result, it is proved that all experimental results with different electrode distance are aligned well with εV^2/L^3 which is a representing electric body force and the change of electric field due to the existence of flame can be estimated by brief 1D steady-state analysis.

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Asymptotic analysis on lean premixed flames with high-temperature unburned gases was performed to obtain the burning velocity analytically. One-dimensional steady reactive flow with sufficiently low Mach numbers was treated, and a one-step irreversible chemical reaction with large activation energies was assumed. Through asymptotic analysis, we obtained the formula for the burning velocity, depending on the temperature of burned and unburned gases and on the mass fraction of fuel. To study the characteristics of high-temperature lean premixed flames, we changed the unburned-gas temperature under the constant-enthalpy conditions where the burned-gas temperature was constant. As the unburned-gas temperature became higher, the mass flux density of the unburned gas increased. This was because of the decrease of the difference in temperature between burned and unburned gases.

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Supercharging the intake air is an effective method of increasing the operating load of Homogeneous Charge Compression Ignition (HCCI) engines because it can reduce nitrogen oxide (NO_x) emissions. In this study, in-cylinder spectroscopic measurements and measurements of exhaust gas components were obtained to examine the influence of the intake air pressure on the combustion characteristics of a supercharged HCCI engine when dimethyl ether (DME) was used as the test fuel. The effect of the intake air pressure on the stable operating region of the test engine was also investigated. The experimental results showed that combustion became more moderate and the combustion period was extended as the intake air pressure was increased under a condition of a constant injected heat value. As a result of a detailed investigation made with a spectroscopic method, it was found that the recombination reaction of CO and O slowed, which caused the moderation of combustion. In addition, it was also found that raising the intake air pressure had the effect of reducing NO_x emissions, which, together with the more moderate rate of combustion, made it possible to increase the operating load. However, it was observed that as the operating load was further increased, rapid combustion could not be sufficiently controlled. Therefore, some means of controlling rapid combustion will be needed in order to operate supercharged HCCI engines at higher load levels.

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For NO_x reduction, it is significant to increase EGR however excessive EGR involves smoke deteriortions. The slightly lower EGR rate than smoke deteriorating EGR rate is thought as maximum EGR rate. This study gives an example to increase the maximum EGR rate from 30% to 50% even at high BMEP operations such as BMEP=2MPa and expect furthermore reduction of BSNO_x. This is achieved by new technologies such as 200MPa fuel injection pressure, 451.3kPa boost pressure at BMEP=2MPa and the improved flow coefficient of intake port to increase the intake air quantity into cylinder. The high flow port realizes about 5% increase of maximum EGR rate, 200MPa fuel injection pressure also allows increasing 5% of maximum EGR rate. Finally, heightening boost pressure from 400kPa to 450kPa contributes to increase a more 5% increase of EGR and it reaches 50% of maximum EGR Rate. The BSNO_x emissions on BMEP=2MPa reduces from 3.5g/kWh to 1.0g/kWh by these process without smoke and PM deteriorations. Using these technologies also effective in improvement of BSFC.

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