Micro-Flow-Sensor (MFS) equipped with a heater at its center can measure temperature difference up and downstream of the heater. MFS is a suitable sensor for determining separation point, since it can detect flow speed and direction near the wall. The sensor is so small that it is difficult to measure directly heat and fluid flow around it by other instruments. In the stage of micro sensor development the mutual guarantee is needed between the experiment of an enlarged sensor model and its numerical analysis. In this paper, a problem of micro sensor is described from a point of micro experimental fluid dynamics by numerical analysis with convection heat transfer around the micro sensor and experiment of the enlarged MFS model.

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dimensional Navier-Stokes equations to simulate directly the flow fields in a medium Reynolds number baffled stirred tank. The rotational cylindrical coordinates with angular velocities are used to express boundary conditions on impellers. On the other hand the stationary cylindrical coordinates are adopted for baffles. When the fluid is water, the phenomena during 60 seconds, which are the sufficient time for obtaining various flow mechanisms and time averaged flow characteristics in a stirred tank, are simulated using this calculation method. The calculated results are in good agreement with the measured data. Then, this study makes a way for direct numerical simulations of various type stirred tank with various type impellers and baffles.

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A lattice gas model with biased random walkers is presented to mimic the pedestrian counter flow in a channel under the open boundary condition of constant density. There are two types of walkers without the back step : the one is the random walker going to the right and the other is the random walker going to the left. It is found that a dynamical jamming transition from the freely i moving state at low density to the stopped state at high density occurs at the critical density. The density profiles of walkers are calculated over the channel. It is shown that the pedestrian counter flow can be simulated by the lattice gas model.

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The molecular dynamics method for the interaction of the gas molecule with the solid wall together with the Monte-Carlo method for the motion of gas molecules is applied to analyze the behavior of a slightly rarefied gas between two walls. The wall consists of platinum molecules, and the gas is taken to be xenon or argon. The Couette flow and the thermal problem for which two walls have different temperature are considered. The slip and jump coefficients, tangential momentum and energy accommodation coefficients are obtained at the wall whose temperature is 300 K. The tangential momentum accommodation coefficient of argon is as low as 0.19. The distribution functions of the reflected molecules are also obtained, and it is found that the Maxwell type boundary condition describes well the distribution function of the reflected molecule.

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This paper deals with the optimal geometry of two-dimensional symmetric Y-bifurcation. The optimal geometry was determined by i) minimizing the time averaged pressure loss of the flow through the bifurcation, ii) minimizing the local maximum value of time averaged wall shear stress gradient. The neural network was utilized to identify the relation between the geometry and time averaged pressure loss or the relation between the geometry and local maximum value of time averaged wall shear stress gradient, and the optimal geometry was determined according to the results of identification. Numerical results showed that the cross-sectional area of the optimal geometry reaches its maximum at the apex and this feature is resembling to the actual bifurcation geometry in the artery. So, it was expected the present study was effective to understand the geometry of artery in the body.

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New types of thermoacoustic sound wave generators, which play an important role in the thermoacoustic refrigerator, are developed. The thermoacoustic sound wave generator consists of hot and cold heat exchangers, stack and resonance tube which is made of stainless steel and Plexiglas tubes, 32 mm in inner diameter and 860 mm long. The theoretical sound wave frequency is 100 Hz. First, two sound wave generators are connected with each other either at the open ends or the closed ends. When they are connected at their open ends, their velocity, pressure amplitude and heat transfer are considerably improved compared with those of independently operated ones. Each phase of both velocity and pressure is inverted automatically. However, when they are connected at their closed ends, their velocity, pressure amplitude and heat transfer are almost equal to those of independently operated ones, and each phase is synchronized automatically. Second, a loop-type sound wave generator constructed of four sound wave generators and four bent tubes is developed. Its sufficient performance is also confirmed.

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Modeling of phenomena and derivation of basic equations have been described about the installation of parachute attaching telecommunication cable in the conduit with bends using spiral airflow. It was clarified that in the bends relatively high friction force generated by contacting and/or attaching the cable to the conduit (pipe) wall in a limited distance yield to a "jump" in the tensile force exerting the cable. At the same time, the evaluation of the friction coefficient between the cable (and/or parachute) and the pipe wall was based upon the hypothesis that an efficient installation of the telecommunication cable using the spiral airflow owed to its reducing effect of the friction force. Through the analysis conducted, the availability of the numerical simulation was demonstrated.

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The response of a turbulent flow in a rectangular cross-sectioned duct to a rough-to-smooth step change in the surface roughness of the short-side walls has been investigated experimentally. The distributions of the primary and secondary flow velocities, turbulence intensities, and turbulent shear stresses have been measured by hot-wire anemometers in seven cross-sections set up in the smooth-duct part. In the core region of the duct cross-section, large secondary currents are maintained over a relatively long distance after the rough-to-smooth junction, and they cause large velocity gradient in the primary flow and large turbulent shear stress there. The streamwise changes of the turbulence intensities are rather complex. In the core region they once overshoot the values in the rough duct just after the rough-to-smooth junction, then undershoot those in the smooth duct, and finally approach an equilibrium state, while near the short-side wall they are decreased quite rapidly and monotonously in the streamwise direction.

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The purpose of this paper is to study in detail the flow over an inclined fence in a turbulent boundary layer, as basic research which issues from promoting heat transfer and the decrease of the pressure drop. The fence height h set in a turbulent boundary layer is 3 mm (u_τh/ν≒75, u_τ : friction velocity, ν : kinematic viscosity) and setting angle of a fence is 20° in the free stream direction. The time averaged velocity profiles in the downstream of the fence ware measured by using a 3-hole pitot tube. We investigated velocity profiles by utilizing polar diagram, logarithmic velocity distributions and velocity defect law. Consequently, It was found that the spanwise velocity profiles are cross-over profiles. We clarified the relaxation process from streamwise direction velocity. Further we investigated in detail the flow direction on the wall which shows the wall shear direction by the oil flow visualization.

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As a fundamental study for the free surface flow blanket of fusion reactors and the lithium target of a neutron source, the turbulence structure of a falling thick film flow with free surface was experimentally investigated. Velocity close to the free surface was reasonably well measured by processing velocity signal from the LDA. Turbulence damping near the free surface in the flow direction was quantitatively presented for the developing thick film flow. Turbulence enhancement near the free surface was observed when the insert of a thin plate was attached to an upstream inner wall surface. Specific profiles of skewness and kurtosis of velocity were observed when the insert was mounted in the upstream inner wall surface.

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The flow fields oftthe opposed jets are characterized by the impact position of jets. It has been considered intuitively that the impact position is determined by total momentum balance of mean flow at each nozzle exit in opposed turbulent jets. In this paper, the flow fields of the opposed turbulent jets with the control pipe in the jet center and the bistable performance of the impact position are investigated. The control pipe can be used for varying the Impact position. And the flow fields with the control pipe are expected to have wide applications in the industry fields. The flow fields are examined by means of measurements of the velocities, static pressure and power spectrum.

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Lagrangian behaviors of solid particles released in an axisymmetric submerged water jet impinging onto a horizontal plane surface have been studied numerically. The impinging jet flow (Re =13000) is represented using a modified k-ε turbulence model proposed by Kato and Launder⁽¹⁾ Trajectories and velocities of the particles are calculated using a one-way coupling Lagrangian eddy-particle interaction model based on Schuen et al.⁽²⁾. Thousands of glass particles (ρ_p/ρ_f=2.45) of 1.05 mm in diameter are released at the exit of the jet. The mean and root-mean-square velocities of particles simulated here show good agreement with experimental data obtained in separate measurements.

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Experimental studies are carried out to clarify the effects of abrasive particle type on the structures of the abrasive water suspension jets. Observations of the jets are conducted at the injection pressure of 12 MPa with seven types of abrasives, two types of steel bead, two types of aluminum oxide, two types of glass bead, and a type of plastic shot. The experiments show that the jet structures are affected greatly by the type and the concentration of the abrasive. By using smaller abrasive particles, the jet becomes compact. However, larger abrasive particles tend to promote the jet breakup. These tendencies are noticeable in the case of the abrasive with high density.

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Experimental studies on aerodynamic characteristics of a flat-plate wing with leading-edge serrations have been made for attack angles from O° to 25°. The apex angle φ of the serration is varied in arrange of 15°, 30°, 60°, 90° and 120°. The lift/drag ratio increases by the leading-edge serration with φ=15°-90°. The leading-edge serration is effective in increasing the stall angle and reducing the drag. The maximum drag reduction of 35% is attained for φ=15° and 30°. There exists interaction between longitudinal vortices induced by the serration and the separated flow. The effect of the interaction is surveyed in terms of distributions of time-mean velocity and turbulence intensity. The flow separation is suppressed by a secondary flow associated with the counter-rotating longitudinal vortices. The momentum defect is smaller in case with serration than without the serration. This is because the longitudinal vortices induced by the serration transport the high momentum fluid of the main flow into the separation zone.

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Rotating cavitation is one of the flow instabilities associated with cavitation, which has been a severe problem for the development of turbopumps of liquid rocket engines because of causing the destructive super-synchronous shaft vibration. Recently, it is argued that rotating cavitation might also induce large repetitive stresses on blades in accordance with the unsteady pressure due to the significant change of cavitating regions. This paper describes about the theoretical prediction of unsteady blade forces working on the cavitating inducer under rotating cavitation. Unsteady pressure distributions and a lift force for a 2-dimensitional flat plate cascade under rotating cavitation are calculated by the linearized free streamline theory based on the unsteady closed cavity model and singularity method.

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Two types of two-dimensional analyses using the singurality method were made to clarify the unsteady characteristics of the cavitation on an oscillating hydrofoil. By a linear analysis based on the assumption of infinitesimal disturbances, typical behaviors of cavitation due to the pitching motion of hydrofoil were made clear for the cases with both partial and super cavitations. By a time marching analysis which allows a large cavity length variation, the effect of the pitching motion of hydrofoil on the transitional cavity oscillation was well simulated. Both of the analyses were validated through the comparisons with the experiments described in the previous report.

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Oscillation control method of the pseudo-shock in a supersonic channel using a dividing porons plate is presented and studied experimentally. The shock waves in each channel interact each other and the oscillation is suppressed. The time-mean position of the pseudo-shocks is stable, and the wall pressure fluctuation is reduced on both the upper and the lower walls. The effects of the length of the plate, the divided area ratio and the porosity of the plate are discussed.

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When the propagating shock wave reaches at the exit portal of a tube, the impulsive wave discharges to surrounding area and the expansion wave occurs from an open-end of a tube in the condition of subsonic flow behind the shock wave. The problem related to the reflection of propagating shock wave at the open-end has become more important subject associated with pulse combus-tors, pressure exchangers and high-speed railway train/tunnel systems. For the case of shock Mach number Ms less than 1.34, the reflected expansion wave generated at the open-end propagates toward upstream of a tube against the direction of the incident shock wave. For the cases of reflection at an open-end with no-baffled tube, Rudinger suggested the empirical equation concerning the imaginary center of reflected expansion wave. In this paper, the improved empirical equation considering the influence of the diameter of a baffle plate at the open-end was proposed. The experiment study using the simple shock tube and the numerical calculatdon using the TVD method were carried out.

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Stress waves induced in elastic solid models by shock waves were studied experimentally and theoretically. For shock-tube experiments, several kinds of solid models were made of transparent acrylic resin and shock waves at approximately Mach 3 were propagated to the models in stationary argon. The schlieren method with a spark light source were employed to visualize shock waves outside and stress waves inside the model. In the schlieren snap-shot photographs, not only shock waves around the models but also stress waves inside the models were observed. Numerical simulations were carried out for shock waves as well as stress waves employing the finite volume method based on the Godunov algorithm. Good agreement was obtained between the experiments and the simulations.

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Helical Screw Expander is a positive displacement type fluid machine. So far, steady simulation methods were carrided out to get quantities of state between the lobes, where the internal leakage is occurred. In these simulations, quantities of state hold constant values in the admission process. However, the disagreements between the simulation and the experimental results are extended at the higher rotor speed. Therefore, the simulation method has to consider the dynamic behaviors at the admission process. In this work, the bondgraphs technique was used to predict the dynamic behavior. Hence, the bondgraphs method improved the evaluation of the performance, especially at the higher region of the rotor peripheral speed. Consequently, the effectiveness of the bondgraphs method to predict the performance on a helical screw expander is confirmed.

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Karman-vortex induced sound is generated from a cylinder in a uniform flow and causes serious noise problem. Recent papers described that the sound was reduced efficiently by attaching another cylinder (called No.2 cylinder) in downstream side to the cylinder (called No.1 cylinder). In this report, we examined the effect due to the length of No.2 cylinder, the intersectional angle between two cylinders and the upstream positioning of No.2 cylinder. It was clarified that the noise reduction in case of upstream positioning is greater than that of downstream positioning. In order to clarify the reason of the noise reduction, we measured the coherence function γ between the fluctuating pressure on the surface of No, 1 cylinder and Karman-vortex sound measured far from the cylinders. As a result, it was revealed that the turbulence from No.2 cylinder promotes the dispersion of the dominant frequency of the fluctuating pressure on No.1 cylinder.

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This paper presents the experimental results of stall recovery margin improvements. Studies have been conducted on a low speed axial flow fan to investigate the stall cessation flow rate with several kinds of injection or suction holes on the end wall. First of all, the fan characteristics for the solid wall have been measured. The hysteresis loop has been observed, but the size of hysteresis loop was not large, so that the stall cessation flow rate was about 17% smaller than the stall onset flow rate for several rotor speeds. Stall recovery margin improvements for both injection and suction were about 3 to 5% larger than stall margin improvements. For the case of injection, the position of maximum stall recovery margin improvements has moved to downstream direction a little from the position of maximum stall margin improvements. For the case of suction, the largest improvement was found at the position of just upstream of leading edge of blade. And negative improvement was not found except very large suction. For the case of injection, comparing with stall recovery margin improvements and stall margin improvements, both values are almost the same with regard to the injection momentum relative to the chordwise.

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The flow field and the train wind reduction effect in the subway station are experimentally examined for three kinds of station model with staircases and tunnels. As the results, prototype model consisting of station and shortened tunnels with orifices can clarify the overall flow characteristics. However, this model is not able to reproduce the time history of the wind velocity at the tunnels and the staircase parts in the real subway. One-station model having the same reduced stale ratio for the tunnels and the station is generally useful to evaluate the wind velocity and the air quantity. Two-stations model connecting two one-station models is most effective to evaluate the transient flow characteristics with high accuracy. In the next place, three train wind reduction methods are tested. The one blower control method which is the tunnel ventilation in accordance with the train wind can reduce the wind velocity at a staircase about 0.5 m/s. Furthermore, two blowers control method can reduce it about 1 m/s. In the case of natural draft method, the wind reduction value is 0.7-1.1 m/s and this reduction effect becomes 1.8 times for the usual staircase with small cross section.

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The motion of microorganism with a flagellum is investigated with a view to applying its propulsion mechanism to the hydrodynamic driving of micro machines in future. Using the boundary element method in the Stokes flow, the speed of advance and the power consumption of the microorganism are numerically determined. Optimizations are done on six non-dimensional parameters that describe the shape of the flagellum and two non-dimensional parameters that represent the shape of the cell body. The optimum shape agrees well with the shape of the actual microorganism except for the cross-sectional shape of the flagellum. Low power consumption and high speed of advance are predicted when the cross section of the flagellum is elliptic with its major axis in the radial direction of the flagellum spiral.

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This paper reports the theoretical analysis and the experimental results on the thermal performance test of a double-glazing air-type solar collector using carbon fiber sheet as a collecting material (air-type CF-sheet collector). The model collector was made by 2 m length and 1 m width with 5 steps arranging CF-sheet. Based on this collector, the heat balance equations were designated and the temperatures, thermal efficiency and the overall heat loss coefficients were calculated. On the other hand, the performance test for CF-sheet collector was conducted with a large-scale solar simulator. It was confirmed that the thermal efficiency obtained from the theoretical analysis agreed with that from the experiments, the double-glazing solar collector was superior to the single-glazing one and the overall heat loss coefficient became higher along with increase in ambient temperature.

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This paper describes a non-contact optical technique for measuring the thermal contact conductance between thin, wafer-like solid samples. In this technique, one solid surface is heated with a modulated laser beam and the corresponding temperature modulation of the other solid surface across the interface is monitored using the reflectance of a probe laser beam. Since each sample can become slightly bent if its edge is compressed by the sample holder, the contact pressure between the samples in the range of 0.8∼10 MPa is calculated using elastic and plastic numerical analysis. The correlation between the contact pressure and the thermal contact conductance is rearranged to derive the function of the calculated contact pressure. Also, proper thickness of glass boards used to fix samples is derived through the reconsideration of sample loading unit.

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Nucleate boiling heat transfer coefficients have been measured during pool boiling of non-azeotropic mixtures of ammonia/water on a horizontal heated wire. The experiment was carried out at pressures of 0.4 and 0.7 MPa and at heat fluxes below 2.0×10⁶ W/m² and in overall range of mass fraction. The heat transfer coefficients in the mixtures are smaller than those in single component substances. No existing correlation is found to predict boiling heat transfer data over the range of mass fraction. In the mixtures of ammonia/water, heat of dilution and dissolution is generated near vapor-liquid interface, when vapor of higher concentration of ammonia is condensed and then is diffused into the bulk liquid, while in the most of mixtures, little heat is generated during any dilution and dissolution. In relation to this heat generated, the effect of the heat of dilution and dissolution on pressure and temperature in a system (pressure vessel) is shown.

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An experimental study is performed on the effects of the initial temperature of a fluid T₀ on free convection heat transfer in a stably stratified fluid. The stratified layer is formed in a rectangular container using sucrose aqueous solution, and is heated laterally from one side at temperature T_h and cooled from the other side at temperature T_c. The experiments are conducted for both cases of T₀ = T_c and T_c < T₀ < T_h to investigate the effects of T₀. After the onset of heating and cooling a series of cellular convection layers is generated at the heating wall for T₀ = T_c, while it is generated at both heating and cooling walls for T_c < T₀ < T_h. Then the resulting growth of the layers and the heat transfer coefficient are different between these cases, especially under the condition of the initially generated cells being thick.

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Natural convective flows of air induced in a two-dimensional, inclined slot were investigated experimentally. The slot consisted of heated bottom plate and adiabatic cover plate. The both ends of the slot were opened to environmental air. These configurations are adoped to simulate the electronic circuit boards placed in electronic equipment. The flow fields within the slot were visualized with smoke and the local heat transfer coefficents of the bottom plate were measured under the various conditions of inclination angles and slot heights. The results showed that the heat transfer from the slot is enhanced markedly by tilting the slot from horizontal. The enhancement of heat transfer was explained by the substantial change in the flow fields within the slot. The above result is considered favorable for the efficient heat removable from the electronic circuit boards by natural convection of air.

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In this study unsteady and chaotic characteristics of the thermal convection fields between concentric annuli were experimentally examined, and they were compared with the previously reported fields in a vertical slot. The inner cylinder was heated by a embedded heater and the outer one was cooled by temperature-controlled cold water, and the 84 wt% glycerol-water solution was used for the present test fluid. The main results are as follows : (1) The region where the characteristic frequency of temperature-variation is detected is located at the upper portion of the region where the secondary cells exist. (2) The time scale of the temperature change at which auto-correlation function becomes 1/e is relatively small in the secondary-cell region, and this corresponds to the result of the natural convection field in a vertical slot. (3) The significant chaotic characteristics in the temperature-variation are determined in almost the same region where the characteristic frequency of temperature-variation is detected, which is peculiar to the field of the present study.

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An ice storage is one of the ways of effective use of thermal energy. So, studies on a slush ice as thermal storage material have been done. We have also been studying on a suspension (slush ice) made of oil-water mixture with cooling and stirring. From our study result, it was found that a kind of additive having amino group (-NH₂) and silanol group (-SiOH) was essential to make the suspension with high IPF without adhesion of ice to a cooling wall. Moreover, formed ices in the suspension were dispersed and granular state and ices did not stick each other. In the present paper, we carried out experiments to clarify the characteristics of the suspension formation process. From the experimental results, it was found that the substance in the suspension was not ice but a compound consisting of ice and additive by a thermal analysis of fusion of the substance. Then, at very small depression of solidification point (about 7°C) all water of the mixture could be solidified by using the additive.

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Selection of the site for ATES is judged by measurement of the apparent thermal diffusivity of the aquifer. Development of the measuring method of the apparent thermal diffusivity is very significant. The unsteady measuring method given by UMEMIYA needed very long time about a day. In this report, the measuring method is developed to enable the measurement in short time less than 12 hours. Field experiments, the measurement of the apparent thermal diffusivity of the aquifer by the newly proposed method were carried out in 3 well, 2 of them in "Solar Aquifer" and the other one, newly dug at "KATAKO" in 1999 as snow melting system. The recovery factor in "KATAKO" was estimated as 15% at most judging with the operational dimensionless charge quantity obtained from the apparent thermal diffusivity. The recovery process has continued in this winter from December 1999 until March 2000.

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A prototype co-generation system for domestic houses is constructed, and cost reduction and energy saving of the system are studied. The system is constructed to use electricity either from utility or generated by the co-generation system. One of those two electric sources is selected by changeover switch according to cost-minimum control. In addition, by converting optimum amount of generated electricity to heat using an electric heater, the working point of the engine of the co-generation system is tried to be shifted to the highest efficiency condition. New control algorithm is developed to select optimum conversion rate of electricity to heat by electric heater when time-dependent demand of electricity and heat is given. Effects of load fluctuation on the operating cost is also studied. Annual energy cost is calculated to be decreased by 30 per-cent by the system.

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The effects of fuel injection velocity and solid surface temperature on the diffusion flames in laminar boundary layers over solid surfaces have been numerically analyzed. The basic equations are solved using a finite-difference method for two-dimensional flow field with one step reaction of methane with air. The flame shape, flow field, diffusion of component gas, heat transfer, etc. are examined. The flame stability limit and the characteristics of the flames near critical conditions are made clear. Although the fuel injection velocity is greatly decreased, the flame stability can be maintained with increase in the concentrations of oxygen and fuel diffusion paths near the leading flame edge. The oxygen and fuel consumption rates in the flame zone are found to be independent of the fuel injection velocity. Aspects of the flame scarcely change even if the solid surface temperature greatly increases depended on the decrease in the thermal conductivity of solid region.

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Recently a lean-rich combustion is drawing attention as a way to decrease the level of NO_x. But the flame structure and NO_x formation process of the lean-rich flame in the unsteady-state was not made clear sufficiently. So we performed the numerical analysis in the unsteady-state in which we took the NO formation mechanism into the consideration by using the Skeletal Chemistry combined with a part of GRI-mech. And we found that thermal NO is generated not only in the high temperature region formed in the downstream of the rich flame, but also in the swell formed in the downstream of the lean flame. In the swell formed in the downstream of the lean flame, the chemical reaction is occurred actively due to the fluctuation of lateral flow that carries CH₄. The faster the lateral flow is, the larger NO mole production rate becomes.

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A concept of "compound-cluster combustion" is proposed in order to investigate an applicability of group combustion theory to practical spray combustion, in which strong turbulent coherent vortex is formed and influenced spray behavior significantly. This turbulent coherent structure causes inhomogeneous droplet distribution and its population, and causes interphase exchange of properties and combustion under the effects of preferential interactions. In application of group combustion ; theory to practical spray combustion, these points were taken into account and phase Doppler measurement (PDA) data was analyzed : there are multiple clusters, characterized by their size and followabiliy (Stokes effect) ; clusters of different droplet sizes are produced at the same time in the flow field ; the turbulent scale on cluster formation should be considered by the droplet's inter-arrival time statistics. In this research, PDA measurement with high sampling-rates and high validation-rates was carried out by optimizing the PDA set-up parameters. The integral length scale of each size cluster and the inter-arrival time statistics of the droplets can be obtained, based on the instantaneous droplet velocities as well as, but also Stokes' number, cluster size and inter-arrival time. The size-classified group combustion number is evaluated by the experimental data to demonstrate the applicability of group combustion theory. The interaction between the turbulent coherent vortex and small droplets of less than 30μm generates essential clusters of the droplets and its combustion can be characterized by group combustion. The size of these clusters corresponds to the integral scale of the turbulent vortices. The effect of turbulent coherent structure on compound-cluster formation is examined and this effect is successfully evaluated by the Stokes effect.

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Recently, the electronic-hydraulic control fuel injection system has potential as a means of reducing NO_x and PM simultaneously, and is already being used in the field of small engines in Japan. However, there seems to be still room for further improvement to the system : to simplify the structure of, to miniaturize, the system, to reduce electronic-hydraulic control power, to improve reliability, to apply the system to any size from small engines to large ones. The point of those improvements is an injector. We did an original improvement to a solenoid valve assembly of the injector. Besides we applied Pascal's law to this study and made a new intensifier style injector. We examined the effect of those improvements by calculations and experiments. As a result, it seems evident that this solenoid valve assembly can be used practically.

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