Measurements are made of the time-averaged and fluctuating fluid forces, the vortex-shedding frequency and the behavior of the impinging leading-edge vortices of a rectangular cylinder forced into rotary oscillation. The rectangular cylinder having the width-to-height ratio B/H of 3 (H : height of cylinder, B : width of cylinder) in which vortices are formed at the leading edge is adopted. The cylinder is forced into rotary oscillation with angular displacements up to α=±5°and the nondimensional frequency f^*H/U₀ (f^* : frequency of oscillating cylinder, U₀ : free-stream velocity)is varied from 0.01 to 0.27, in which the lock-in region is included. It is found that the fluid forces acting on the oscillating rectangular cylinder are strongly dependent on the impinging leading-edge vortices rather than the wake vortices. Also, it is recognized that the fluctuating fluid forces are mainly generated by the phase shift of surface pressure on the basis of the movement of the impinging leading-edge vortices along the side surface.

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Fluid forces (drag and lift force) acting on a rotating sphere in a homogeneous linear shear flow are numeriacally studied by means of a three-dimensional numerical simulation based on a marker and cell (MAC) method. The effects of particle rotation speed, shear rate of fluid and particle Reynolds number Re con the fluid forces are estimated under various conditions from numerical predictions of drag and lift force. The results show that average lift force acts on a stationary sphere from the high-speed side to the low-speed side in a homogeneous linear shear flow with high particle Reynolds number of Re>100. The direction of the lift force is quite different between low and high particle Reynolds numbers. The difference can be explained in terms of the pressure acting on the surface of a sphere. The direction of the lift force for high particle Reynolds numbers is also examined through a preliminary. experiment in glycerin solution flow with a linear shear.

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A numerical method for simulating a three-dimensional dispersed multiphase flow was proposed in the present study. The method is based on a two-way particle tracking method, which takes into account the effect of the dispersed phase on the continuous phase and vice versa. The field equations of the method are compatible with those of conventional multi-fluid models. In order to demonstrate the potential of the method, laminar bubbly upflow in a vertical square duct was simulated by taking the Eotvos number and a bubble size distribution as parameters. As a result, we obtained typical bubble distributions, i. e., wall-peak, core-peak and intermediate distributions. A void wave in the flow direction was also observed in the calculated core-peak distribution, which indicates that the method has the potential for predicting flow pattern transition from bubbly flow to slug flow.

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Single bubbles rising through stagnant liquids were calculated using a particle tracking method (PTM) and an interface tracking method (ITM) to examine whether or not the two-way particle tracking method proposed in the previous study can give good predictions for bubble-induced liquid velocity fields Comparisons of the two methods were conducted for two types of three-dimensional bubbles : one is a spherical bubble with a creeping flow and the other is a spherical-cap bubble with a wake. It was confirmed that liquid velocity fields predicted by PTM for both types of bubbles agreed qualitatively with those predicted by ITM, and PTM can accurately predict a liquid velocity distribution in a wake region, provided that the bubble diameter is greater than the computational cell size.

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In this work, the two-dimensional square driven cavity flow problem is solved by the finite difference method with a uniform mesh. The 3 rd-order upwind scheme and the 5 th-order upwind scheme are applied to the convective term in the vorticity transport equation. It is necessary that the approximation of the convective term is treated carefully. First, therefore, the accuracy of the convective velocity is considered. As a result, it is clarified that accuracy of convective velocity is important in the numerical flow analysis in which vorticity and stream function are unknown quantities. Next, comparison of the 3 rd-order scheme and the 5 th-order scheme is carried out. Finally, by adopting of the highest-order calculation condition, more accurate results than Ghia's data for high Reynolds numbers are obtained. The steady solution can be obtained for Reynolds numbers as high as 25000.

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Effects of impulsive change in pressure gradient in a two-dimensional turbulent channel flow have been experimentally investigated. The rapid change of pressure gradient was obtained by passage through a contracted region. Turbulent intensities of velocity fluctuations and Reynolds shear stress following the removal of rapid pressure change were measured by means of a hot-wire anemometer. The statistical properties, i.e., energy spectra, length scales of turbulence, skewness / flatness factors and turbulent diffusions, were investigated. Turbulence intensities and Reynolds shear stress increase due to pressure gradient, however, the correlation coefficient of Reynolds shear stress depends slightly on pressure gradient and is constant across the chennel. The length scales are considerably smaller than those in equilibrium turbulent flows. The turbulent diffusions((U²V)^^^- - (UV²)^^^-) are negative in the near-wall region. The results reveal that the sweep event of bursting is strengthened by the rapid change in pressure gradient.

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We describe our research on the demagnetizing factor of a water-based magnetic fluid. The magnetization characteristic determined by Monte Carlo Method is considered as the standard characteristic which is not influenced by the demagnetizing field. By comparing the measured magnetization characteristic with the above-mentioned standard characteristic, the demagnetizing factor is clarified.

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The coherent structure for the plane wall jet under the self-preserving pressure gradient was analyzed to examine the effect of velocity ratio U_m/U_e on the ensemble averaged pattern which, in particular, corresponds to the trunk of a pair of spanwise vortices. Three values of velocity ratio U_m/U_e were used in the range of 2.0 to 4.0. The VITA technique was employed to detect the longitudinal velocity signals. It was inferred from the ensemble averaged patterns of u- and ν- fluctuating velocities that a pair of counter-rotating spanwise vortices has the same event independent of the velocity ratio. The peak ratio R_p in the ensemble-averaged pattern, however, decreases with decreasing velocity ratio. The mean period of the event also decreases with decreasing velocity ratio, while the mean frequency of the event increases. From these results, it was found that the spatial scale of a pair of vortex structures decreases with decreasing velocity ratio.

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Axial velocity distribution in an I₂-seeded Ar free jet is investigated by the laser-induced fluorescence (LIF) technique using a ring dye laser with 500 kHz linewidth. Since the translational temperature in the flow region is low, the hyperfine structure due to the nuclear spin of I₂ molecules is observed in the spectrum of I₂B³II⁺_ou&herr;X¹Σ⁺_g bands. The spectrum shape is explained by the quantum mechanical theory and the simulated spectra coincide with our measurements. First, the possibility of the translational temperature measurement based on the hyperfine spectrum shape is discussed. Then, axial velocity measurement is performed and the results are found to be in good agreement with those of Ashkenas & Sherman. The applicability and the velocity resolution limit of our measurement technique are also discussed.

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A jet under a free surface can induce sloshing in a tank without an oscillating external force. In the previous study, the authors proposed a new growth model of self-induced sloshing caused by a vertical plane jet. The model was based on a feedback loop which simply simulated the interaction between the jet and the free surface. The dependence of sloshing on the tank geometry, water depth and inlet velocity was qualitatively evaluated. In this study, the model was applied to self-induced sloshing caused by a horizontal rectangular jet. Under a certain geometric condition of a rectangular tank, 1st and 2nd mode sloshings were observed The growth of multimode sloshing was qualitatively explained by the model. The self-induced sloshing was considered to be excited by a jet-surface interaction regardless of the incident jet angle to the surface.

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This paper is conerned with the self-excited oscillation in a shear layer of an axisymmetric jet when a fine screen is placed normal to the axis of the jet. The diameter of the nozzle exit is 28 mm and the exit velocity is 10.4 m/s corresponding to Reynolds number 1.99×10⁴. Screens with three different mesh sizes are employed. In the experiment the screen is moved in the direction of the jet axis. The shear layer starts to oscillate periodically and simultaneously a pure tone is generated due to the impingement of the jet upon the screen. The frequency varies in the same way as in the jetring system. It is recognized that the configuration of the peaks in the velocity spectrum reflects that of the peaks in the sound spectrum. After passing through the screen, the periodic oscillation in the velocity remains at the location twice the nozzle diameter away from the screen.

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The vibration of a flexible tube induced by the pulsatile flow of an emulsion was studied experimentally. Three flexible tubes (thin silicon tube, thick silicon tube and vinyl tube) were used and their vibrations were measured using a high sensitive gap sensor. Experimental results showed that the pulsatile flow of emulsions had an effect to increase the amplitude of wall displacement compared with the pulsatile flow of water. In addition, it was suggested that the relaminarization of pulsatile flow had a strong effect on the behavior of flexible tubes.

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Wavy interface generation is an interesting characteristic of explosive welding. There have been many theoretical and experimental discussions of the mechanism of wavy interface generation, but there is no consensus of opinion as yet. We report a numerical approach to the analysis of the mechanism of interface wave generation in explosive welding. The phenomena of the interface wave generation are calculated using a two-dimensional finite difference scheme for elastic-plastic materials. In this simulation the equations for a symmetric collision between copper plates are solved. The concept behind this study is that the wavy interface and vortex streets are caused by the velocity distribution of shear flow and periodic disturbances at the interface. The calculation results show the deformation process of the wavy interface and we obtain qualitative agreements between numerical and experimental results.

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In this study we experimentally investigate lubricating characteristics or metallic contact characteristics at a small end bearing of a connecting rod in reciprocating compressors for household refrigerators. In practical operation of the compressor, a periodically changing load acts on the small end bearing and a piston pin rotates periodically in the bearing bore during one revolution of the shaft, which makes formation of oil film at that bearing difficult. In order to observe the condition of metallic contact at the bearing, electrodes were mounted on the sliding surface at the bearing and variations of the contact resistance were measured using a simple electric circuit. Combinations of refrigerant and refrigeration oil used in this study were HFC-134a/ester oil and CFC-12/mineral oil, and the measurement was performed under different operating pressures, temperatures and rotational speed of the compressor. It was concluded, from the observation of electric signals from the electrodes, that there occurs partial metallic contact at the small end bearing during one revolution of the compressor, there exists a correlation between the metallic contact rate and the value of U/F_c (ratio of sliding velocity to load) as the metallic contact increases with decreasing U/F_c, there is no significant difference in lubricating characteristics between HFC-l34a/ester oil and CFC-12/mineral oil.

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An adaptive grid method that uses an elliptic equation is developed and applied to shocked flows. In this paper, two improvements are introduced to the adaptive grid method. In the adaptive grid method of the elliptic type, construction of a control function, which is the source term of the Poisson equation and can control the grid distribution, is key to the generation of high-quality grids. Instead of an actual solution, modified solution is used for estimation of the control functions with effective grid control for a shocked region. Grid skewness is one of the problems in the solution-adaptive grid method. To avoid severe grid skewness and attain more flexible adaptive gridding, the adaptive grid method is combined with an overset grid method. Overset subgrids are placed in regions where shock waves stand and the adaptive grid method is applied to the these subgrids. The applicability of the present method to the supersonic channel flows is demonstrated.

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A new method for solving the primitive variable formulation of the incompressible Navier-Stokes equations on the non-staggered grid is presented. The spatial derivatives of the momentum equations are discretized by the second-order centered finite difference approximation on the cell interfaces, and the fluxes on the non-staggered grid are estimated from the simple average of the cell interfaces. The resulting system of ordinary differential equations in time is integrated by the forward Euler scheme. The Poisson equation for the pressure is discretized in the same manner as the momentum equations and solved by the successive-overrelaxation (SOR) method. The present method satisfies the divergence-free condition, i.e., the continuity equation, at each time step. As the test problem, square driven cavity flows are considered. The results obtained by the present method are compared with those of the marker-and-cell (MAC) method. The results show that the present method gives solutions comparable to the MAC solutions, and that the allowable time step is larger than in the MAC method.

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The finite difference method has developed the numerical analysis of compressible flows. In particular, TVD (total variation diminishing) has improved the modeling of shock waves of compressible flows. Numerical results which are in good quantitative agreement well with the experimental results, have never been obtained. One of the reasons is the insufficient resolution for complex reflection of shock wave. Many grid points are necessary to attain the high resolution. Current supercomputers cannot resolve the abovementioned difficulty. Meanwhile, higher calculus processing of more than one teraFLOPS will be required for future numerical computations by LES and DNS.Multiple-instruction multiple-data (MIMD) is considered to be the only type of computer which satisfics the above-mentioned requirement. Difficulty is caused in the development of the application because each processor in MIMD has an independent main memory. In the present paper, the fundamental problem of parallel computation is discussed in numerical analysis of compressive flows using a massively parallel computer (Fujitsu;AP1000). The effect of the method of communication between each processor and the method of dividing the computational area on parallel calculus speed is also discussed.

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In this paper, we have proposed the hybrid streamline-upwind finite-element method using the discrete del operator for the case of mixed elements, which has already been described for the case of a hexa element in the previous paper. Generally speaking, it is the demerit of the finite-element method that it tapes much time to construct computational grids. Therefore it is important to extend the theory to the mixed-element case in order to save time in constructing computational grids in the complex computational area. The main content of this paper is as follows. First, we define the streamline-upwind shape function of each element using a solution of a steady advection-diffusion equation Second, we have proposed the discrete del operator for the mixed-element method, which is defined as an element average of the gradient of the shape function in the discrete space.

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An experimental study was carried out to investigate the behavior of shock waves on a three-dimensional axisymmetric waisted body with an adverse pressure gradient region in transonic flow. This included an experiment in which a tripping wire was placed on the tip of the waisted body so that transition to turbulence was excited. Based on the experimental results, the behavior of shock waves was classified into three types according to shock features and free stream Mach numbers. For type 1, the features of the flow were unsymmetrical. For types 2 and 3, shock motions could be regarded as axisymmetrical. The behavior of shock waves when the tripping wire was present did not differ from that without the tripping wire.

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This paper is concerned with the wing structure and the aerodynamics of a flying dragonfly. The structural properties of dragonfly wings were studied through the measurements of some morphological parameters. The wings of the dragonfly Sympetrum infuscatum were examined with a scanning electron microscope. Some structural features of dragonfly wings were revealed. Some aerodynamic aspects of dragonflies were considered on the basis of experimental results. The relationship between flapping frequency and total weight for dragonflies was found through dimensional analysis.

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In this work, we developed a theoretical algorithm to design a train shape for alleviating the booming noise caused by a train moving into a tunnel. In past studies, the authors clarified that the strength of the booming noise is proportional to υ_wall which is defined as a lateral velocity component at the height of a tunnel wall in a steady flow field around a train. υ_wall is theoretically obtained as a function of a train shape with the small perturbation theory. With these relations, a train shape is theoretically designed so as to minimize υ_wall. This algorithm is applied to an axisymmetric flow under practical high speed conditions. The optimized train shape is obtained in a very short CPU time and the strength of the booming noise is reduced by about 20%. The efficiency of the optimized shape is verified by an unsteady numerical simulation of the flow field of the train moving into the tunnel. The results indicate that this algorithm can be an efficient method for designing a train shape that alleviate the booming noise.

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In the development of continuous high-power gas laser systems, the supersonic free-vortex aerodynamic window is one of the key technologies for extracting a laser beam from the laser cavity. The present paper describes the design procedure of the two-dimensional supersonic free-vortex nozzle, and demonstrates the operating conditions of the window, taking into account the phase transition of the working fluid in the nozzle expansion process and the operating conditions of the supersonic diffuser. Generally, the high-power laser will be operated in the atmospheric environment without auxiliary equipment, i. e., a heater installed in the nozzle supply and/or a vacuum pump connected with the ventage of the supersonic diffuser. Therefore, the temperature of the working fluid at the nozzle supply is nearly 300 K, and the back pressure of the supersonic diffuser is inevitably atmospheric pressure. Hence, when using nitrogen gas as the working fluid in such an environment, the pressure ratio of the laser cavity to the atmosphere, which can be achieved with no phase transition, is about 20. In order to attain the higher pressure ratio of about 50, helium gas is required as the working fluid.

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The present study deals with the control of leakage of pollutants from exit portals of road tunnels. This report, supplementing the 1st report, describes an accuracy of the theoretical formula for concentration distribution and leakage ratio of the ventilation method, consisting of a transverse ventilation system with an extraction shaft. The results of this study confirm the effectiveness, both in theoretical and experimental terms, of the present ventilation method as a measure against environmental pollution around exit portals of road tunnels.

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Discrete tone noise generated in a uniform jet flow on a two-dimensional wing was investigated. Discrete tone noise is generated by a self-excited feedback loop formed by the acoustic field and the unstable boundary layer. In this work, we show the calculation method and results of flow fluctuation amplitudes, phase delays and the growth factor, for the unstable boundary layer. The theory of stability of laminar flows and the differential approximation apply to this method. The results are compared with experimental data and almost coincide with them. It is clarified that the flow fluctuation amplitude ratio on the suction side of the wing is larger than on the pressure side The growth factor and the length of the flow fluctuation waves are estimated for all frequencies

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In order to study the effects of the translational energy of incident metal atoms on the process of condensation and crystallization of thin films, we developed a method of vacuum deposition of velocity-selected metal-vapor atoms. A mechanical velocity selector for a neutral Ag beam was constructed and its performance was confirmed by measuring the velocity distribution of the velocity-selected beam. The velocity-selected vacuum deposition of Ag beam on (001) NaCl substrates reveals that the condensation coefficient of Ag on (001) NaCl depends greatly on the substrate temperature and that at the substrate temperature of 300°C it is much smaller than unity. Results also show that the effect of the deposition rate on crystalline structures is rather large and thin films deposited at a low deposition rate showed better epitaxial growth even at a lower substrate temperature.

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The transition boiling heat transfer was analyzed by considering the formation, evaporation and dryout processes of liquid layers beneath individual bubbles. In the low-superheating region, the heat flux is mainly due to the evaporation of the microlayer. In the high-superheating region, the evaporations of both the microlayer and macrolayer play important roles in heat transfer. The predicted fraction of wetted area and heat flux of transition boiling showed good agreement with experimental data reported in literature.

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A correlation is developed for evaporation heat transfer inside a spirally grooved tube, and compared with the experimental data. First, heat transfer coefficients for pure refrigerants were correlated in a form such that two-phase flow pattern was taken into account. Next, a correlation for binary mixtures was derived from the correlation for pure refrigerants and the thermodynamic relations for mixtures. This is based on the model described in the previous report. The predicted heat transfer coefficients agreed with the experimental data with a mean deviation of 7.4% and 8.8% for pure refrigerants (R11, R114, R123) and binary mixtures (R11/R114, R123/R134a), respectively.

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Three-dimensional numerical simulation has been performed for flow over a backward facing step in a rectangular duct. The simulations were carried out for several cases of different aspect ratios and of different Reynolds numbers. The expansion ratio was kept constant at two throughout this study. The flow was found to remain steady under all studied conditions, except for the case of Re=375, in which the flow became periodically unsteady. Numerical results were compared with other investigations and found to agree well with experimental data. Close attention was paid to the distribution patterns of both Nusselt number and the skin friction coefficients on the bottom wall. It was revealed that an aspect ratio of as large as AR=16 at least was needed to obtain a two-dimensional region near the centerline at Re=250, and that at lower Reynolds number, the two-dimensional region became wider. We also reported that the maximum Nusselt number did not appear on the centerline but near the two side walls in every case.

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The present paper describes the heat transfer characteristics of an annular turbulent impinging jet with a confined wall. The local temperature distribution on the impingement surface was obtained using a thermosensitive liquid crystal sheet and an image processor. The net heat flux was evaluated by considering the heat conduction in the heated section and the thermal radiation between upper confined insulated wall and impingement surface. Isothermal lines and iso-Nusselt number lines were obtained in two-dimensional form. Effects of diameter ratio, distance between nozzle and impingement surface and Reynolds number on radial distribution of local Nusselt number were examined. Experimental equations of local Nusselt number were obtained in power-law expression of r/r_p for major and minor flow regions.

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Three-dimensional unsteady separated and reattached flow over a blunt flat plate in a channel is analyzed by numerical simulations of Navier-Stokes equations, and the heat transfer characteristics are also numerically clarified. The results of three-dimensional unsteady calculations at low Reynolds number are presented. The flow in the recirculation region is three dimensional and the separated shear layer around the center of the plate becomes unstable. As a result, vortices are periodically shed from the reattachment flow region. Such a vortex exhibits a hairpin-like structure and greatly influences the heat transfer. The horseshoe vortex near the endwall is steady, and the Nusselt number therein is larger than that near the center of the plate.

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We propose a Fredholm-type boundary integral expression of the forced convection heat transfer coefficient from an object. When the Fredholm's kernel function is obtained by a numerical simulation of the forced convection field, it is possible to predict the local heat transfer coefficient from the object with arbitrary surface temperature distributions. Moreover, this expression can be easily applied to the boundary element method (BEM), and then the convection-conduction conjugated heat transfer problem can be formulated as a heat conduction problem, Some examples demonstrate the usefulness of the proposed expression.

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The effects of natural convection on self-ignition of solid fuel heated by external radiation were studied numerically. The numerical model includes thermal heating and subsequent degradation reactions in the solid phase with heat and mass transport of evolved degradation products into an atmosphere containing oxygen. The combustible fuel component of the product gas is mixed with oxygen to produce premixed gas and the heating of the gas accelerates the oxidation in the gas phase leading to spontaneous ignition. The induced natural convection was found to play a key role in the heat and mass transport, and hence in the time-dependent process leading to ignition. In the numerical calculation the magnitude of gravity was changed continuously to study its effects on the ignition time and ignition point. Effects of oxygen concentration in the atmosphere were also studied.

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A method of measuring temperature and thermal properties of nonconductive fluids was experimentally studied, where 1ω and 3ω components of the voltage drop across a thin metal wire probe heated with an AC current of frequency ω were measured. The temperature distribution of a weak natural convection plume from a horizontal wire in water was visualized by this method and it was shown that background noise and self-heating of the probe limit the measurement resolution. Thermal conductivity measurements were performed for air, water, ethanol, etc. using a 10μm-diameter platinum wire, with applied AC frequency ranging from 0.1 Hz-10 kHz. Since thermal conductivity is derived from the measured 3ω component by comparing with a thermal conduction model, the effect of natural convection from the probe itself was important and a restriction on applicability of the method was obtained in terms of the Rayleigh and Fourier numbers.

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Experimental and numerical investigations are carried out on the melting of a vertical ice plate into a calcium chloride aqueous solution inside an insulated rectangular cavity. The ice plate melts spontaneously even when there is no temperature difference between the ice and the liquid. It is found that the temperature at the melting front decreases monotonically from the initial temperature due to the mass-diffusion controlled melting of the ice. The melting rate is significantly affected by a combination of natural convection with the temperature and concentration of the liquid. It is shown that the numerical model predicts well the melting rate and temperature drop at the melting front.

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Linear stability analysis was performed for channel flow with two ribs attached to one wall. Effects of perturbations with an infinitely small amplitude on a fundamental steady flow in the channel were numerically investigated. The fundamental flow corresponds to one of the steady solutions of the Navier-Stokes equations. Time-asymptotic solutions of the perturbation equations reach the least stable mode of the channel flow. Growth or decay of the perturbations was supposed to occur everywhere in the flow with a constant amplification factor, since the logarithmic value of the maximum transverse perturbation velocity of the least stable mode changed linearly with time at all monitoring locations in the channel. In addition, a direct numerical calculation was performed using the two-dimensional Navier-Stokes equations to investigate the characteristics of nonlinear stability, the results of which showed a similar growth pattern to those derived from the perturbation equations. The flow instability with an increase of the Reynolds number was found to depend on the value of the source functioning term of the perturbation vorticity equation derived from the perturbation equations.

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Transient heat release characteristics of a rectangular latent heat storage vessel packed with shape-stabilized phase change (solid-liquid) material (PCM) are investigated numerically with the finite difference technique. It is found that the heat release characteristics are greatly affected by the flow direction of the heat transfer medium since natural and forced convections coexist in the heat storage vessel. It is clarified that the thermal efficiency of the latent heat storage system is obtained by an upward flow along the vertical PCM for heat release process The effect of the inlet velocity and the inlet temperature of heat transfer medium and the dimensions of the phase change material on transient heat release characteristics of the latent heat storage system are also revealed in the present study.

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The effects of the components on the dynamic behavior of a directly combined binary turbine system are investigated using the network model which was discussed in the previous paper. In this model, the vapor flow rate and turbine torque are used to define the through variable and the vapor pressure and rotational speed are used for the across variable. The system components are represented as network elements. In this paper, taking the R11 evaporator as the main component, we investigate the effects of the constituents and rating on the characteristics of the system in detail. As a result, it is shown that the overall conductance of the vapor generator influences the load allotment between two turbines, and R11 volume in the R11 vapor generator influences the time constant on its responsibility. In addition, the dynamic behavior of the system using an R11 evaporator which has a different rating is clarified. These simulation results obtained with our network model are shown in terms of the step and frequency responses, taking account of their steady state characteristics.

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The effects of the installation of division walls in large-scale furnaces for thermal electric power plants are demonstrated by numerical analysis of combined radiative and convective heat transfer in the furnaces using a radiative ray tracing method. The changes in the profiles of gas temperature and wall-heat flux and in the furnace efficiency are calculated for different numbers and sizes of the division walls. From the analysis, the following results are obtained. 1. The installation of division walls reduces the average gas temperature and maximum wall-heat flux and increases the furnace efficiency. 2. Among the configurations of division walls with the same surface area, the ones with walls which extend to the center of the furnace have the higher thermal efficiency.

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This experimental study examines pressure drop due to pipe friction when a surfactant is added to (a) flowing water and (b) flowing water/particle slurry for the purposes of reducing power supply when transporting slurry by pump, and improving the capacity of heat transportation fluid. The following results were obtained. Pressure drop in the case of (b) in which mixed particles account for about 12% of the fluid volume 25∼50% more than in the case of (a). When transporting the water/particle slurry containing the surfactant, it is advisable to reduce the velocity and control the Re number to approximately 3×10⁴. If particles included water/particles slurry are replaced by microcapsules that have the thermal energy storage effect due to their latent heat the density of heat transportation of this slurry becomes twice that of water, and pump power is reduced to half that of water.

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A two-stage light gas gun has been developed to accelerate a projectile to supersonic velocity. The first stage of the gas gun is filled with a combustible gas mixture. The second stage is filled with a light gas. A free piston is located between them to compress the light gas which accelerates the projectile. The performance of the gas gun was evaluated under various experimental conditions. The projectile velocity was measured using several magnetic detectors, We plan to use this gas gun in a ram accelerator. In order to visualize the flow field around a projectile, a two-dimensional projectile is used. Consequently, the launch tube of the gas gun has a rectangular bore.

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A prototype of a free piston Vuilleumier heat pump (FPVM) was designed and manufactured in order to research the basic FPVM performance characteristics at self-excited vibration. The FPVM has a cooling capacity of 3.2 kW and a cooling COP of 0.6 at self-excited vibration. Dependences of the dynamic motion of the displacers and the FPVM performance on the mean gas pressure, hot gas temperature, and hot and cold water temperatures were investigated experimentally and analyzed using a simple 2nd order isothermal simulation combined with a linear analysis. The performance characteristics of the FPVM when a hot displacer and a cold displacer were and were not connected by a spring were examined and discussed. There was no qualitative difference between the FPVM's. It was found that the simulation results agreed well qualitatively with the experimental results and that the simulation could be used to analyze the FPVM performance characteristics and to design a practical machine.

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This work investigates experimentally a novel heat-regenerating burner capable of operating at high temperatures and over wide fuel-air ratios, including ultralean mixtures. A high-efficiency burner consists of a heat exchanger (regenerator) and a combustion chamber. The heat regenerator is a rotarytype, and is made of ceramic ; the exit port of the regenerator is a burner port. Heat is stored in the ceramic channel walls, which pre-heats the inlet fuel-air mixture to a high temperature prior to combustion. Both temperature profiles and species concentration profiles in the combustion chamber have been measured, and the heat transfer and combustion performance has been characterized. For the case of constant heat generation, steady combustion is established over a wide range of fuel air mixture ratio from 0.2 to 6.

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An analytical model developed to calculate the radiative energy transmission through a fibrous layer is verified by the experimental results obtained via measurement of the transmittance of a He-Ne laser beam through nickel-fiber sheets with a large size parameter. The model is used to calculate the radiative energy transmission by the Monte Carlo method and the optical characteristics of a fiber with large size parameter are estimated by the method developed by Yamada et al. Which considers the diffraction and reflection by the fiber. The following results are obtained. The results of the analysis agree very well with the experimental ones. The directional profile of the transmitted energy becomes flatter when the thickness of the fibrous layer is increased. When the number of fibers with orientations other than parallel to the fibrous layer is increased, the transmittance is increased. Even when fibers have varying diameters in the range of 20∼28μm, the transmittance is the same as in the case of the fibrous layer with uniform average diameter of 24μm.

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Since August 1994, spectral measurements of the global and direct insolations have been carried out by the authors. According to the intensity of the insolation, the results measured were arranged by classifing into rank of l00 W/m² each ; then, comparing the insolation with Bird's model, the factors of solar altitude, turbidity of atmosphere, precipitable water and albedo of the earth were investigated. Consequently, on a clear day on which cloud amount was less than six, the spectra corresponding to the global and direct insolations could be estimated. Different shapes of the spectra in summer and winter depended on the precipitable water ; the spectrum of the direct insolation was affected by the turbidity and precipitable water, while the spectrum of global insolation was hardly affected by these factors. In addition, on the basis of Bird's model the direct insolation and transmittance of atmosphere were calculated under several atmospheric conditions, and the influence of solar altitude to the transmittance of atmosphere was clarified.

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The effect of strain rate on NO_χ emissions in a methane air counterflow diffusion flame is numerically analyzed with detailed chemistry. First, the kinetic mechanism is revised and tested by introducing ammonia into the fuel. Comparison of the experimental results with the computed results showed that NO formation is well predicted by the present detailed chemistry. NO_χ formation at high air temperature is then calculated by increasing the strain rate from 10s^-1 to 12800s^-1. The results showed that NO_χ emission decreases dramatically with the increase of strain rate and that extinction limit is greatly extended with the increase of air temperature. Furthermore, the sensitivity and production rate analyses are made. Important elementary reactions and formation routes corresponding to NO_χ emissions at different strain rates are presented and discussed. Comparisons between prompt NO_χ and thermal NO_χ are made. Quenches of thermal NO_χ and NCO and CN recycle routes at high strain rate are identified.

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Laser sheet tomography was applied to the visualization of the cross section of a spray. In this method, fluorescent dye, eosine-Y(C₂₀H₆Br₄Na₂O), was used at a concentration of 10 g/1 of the injectant, water, and the light source which illuminated the spray was a Nd : YAG laser (532wavelength, 20ns pulse width) in laser sheet tomography. The thickness of the laser sheet which was scattered by the spray was measured to elucidate the effect of the concentration of fluorescent dye in the injected liquid. In the case of water without eosine-Y, multiscattered light-illuminated drops were observed outside of the laser sheet ; therefore the thickness of the laser sheet increased. However, in the case of water with eosine-Y, there were few drops which were illuminated by the multiscattered light, and only drops which existed within the laser sheet scattered green laser light and emitted the yellow fluorescent light of eosine-Y.

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This study deals with the effect of the viscosity of the ambient gas on the atomization process of a diesel spray. The liquid fuel is injected through a single-hole nozzle (ln/dn=0.75 mm/0.25 mm)with the injection differential pressure of 16.2 MPa inside a constant-volume vessel under a high-pressure field at room temperature. In practical combustion chambers of diesel engines, the viscosity of the ambient gas varies mainly with its temperature. In this experiment, various gases (CO₂, N₂, Ar, Ne, and Ar+Ne) were utilized for the ambient atmosphere in order to change the ambient gas viscosity. The vaporization of fuel drops was negligible. This study, revealed that the higher the viscosity, the more the spray spreads in the radial direction, thus the spray angle increased and tip penetration decreased. The droplets became smaller and were distributed in the inner region of the cold-state diesel spray under high ambient viscosity conditions. Further more, it was found that processes of ligament formation in the liquid jet and initial atomization were affected by kinematic viscosity ratio between the liquid fuel and ambient gas, and the spray dispersion and mixing process in the downstream region was affected only by the ambient gas kinematic viscosity.

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This study was aimed at reducing CO₂ emission from incineration of waste. The fundamental idea is that the incineration process is divided into a high-temperature pyrolysis of waste and a combustion of gaseous products of the pyrolysis, and part of the constitutive carbon atoms in waste is fixed as solid carbon in ash. In addition to gas range, microwave heating is employed to avoid the difficulties originating from the very small effective thermal conductivityes of waste in the pyrolysis process. Photo process copy paper was used to represent waste in this study, since more than half of office waste is wastepaper. The pyrolysis process was tested in a microwave oven as well as in an electric furnace. The results show that two-thirds of the constitutive carbon atoms in the paper are fixed in the residue. After subtracting the amount of CO₂ emission from a thermal power station for the electricity needed by the microwave heater, 35% of CO₂ emission is reduced as the net.

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A pancake-type constant-volume combustion chamber was used to investigate the combustion and NO_χ emission characteristics of propane-air and hydrogen-air mixtures under various charge stratification patterns, which were obtained by variations of injected mixture concentration and ignition spark timing. A planar laser-induced nitrogen dioxide fluorescence technique was applied to measure the mixture distribution in the test chamber. The results show that under the rich side of overall excess air ratio, the combustion speed of the homogeneous mixture was slightly faster than that of the stratified mixture. When the rich mixture was near the spark ignition point, the combustion speed was fastest under the lean side of overall excess air ratio. When the mixture concentration near the spark ignition point increased, NO_χ emissions increased under the lean side of overall excess air ratio but decreased under the rich side.

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There is a gradient of fuel concentration in the spray of conventional direct-injection diesel engines. Therefore, a region of stoichiometric mixture ratio exists in the injected spray and a high concentration of NO_χ is produced. In this study, fuel injection timing was widely advanced to promote the mixing of fuel and air. Using this injection method, the engine could be driven with premixed lean diesel combustion (PREDIC), and NO_χ emissions were greatly reduced. To avoid the fuel spray contacting the cylinder liner, the fuel was injected by two side injectors simultaneously. The two sprays from the side injectors collided with each other and remained in the center region of the cylinder. Thus mixing of fuel and air was promoted by a long ignition delay period. In the case of conventional injection methods, NO_χ could not be reduced to under 400ppm (λ=2.7). In contrast, in the case of PREDIC, NO_χ emissions were reduced to as low as 20ppm (λ=2.7).

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