Pseudoshocks in axisymmetric radial flows between parallel walls were observed experimentally in full circular forms, and were simulated numerically, solving the 2D-Reynolds averaged Navier-Stokes equations. The objective of this study is to investigate the structure of the circular pseudoshock and the influence of flow parameters. In the simulation, a 2nd-order-accuracy Harten-Yee TVD scheme was used for high resolution and numerical stability, and Baldwin-Lomax's algebraic model was used for turbulent flow. Both experimental and numerical results on the pressure distribution agreed well. Then the influence of parameters on the shock structure was deduced through numerical simulations.

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The study of unsymmetrical nozzle flow is important not only for basic research in gas dynamics but also for mechanical applications. In the present study, six kinds of unsymmetrical nozzles which had different divergence angles and wall lengths were used to analyze the effect of the nozzle configuration and Mach number at the nozzle entrance on the flow. The effects of Mach number at the nozzle entrance and the divergence angle of the nozzle on the oscillation of shock wave were investigated experimentally. Furthermore, the effect of wall length on the direction of the flow was investigated. A schlieren optical system, and a Mach-Zehnder interferometer composed of an Argon laser (CW) as the light source with acousto optic modulators (AOM) were employed for visualization of the flow.

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A series of subsonic diffusers with a shock wave at the inlet was tested to establish a design technology in the development of a supersonic airintake. The effects of diffuser geometry and pressure gradient on the diffuser performance were investigated. The diffuser geometry with a constant Mach number gradient in the streamwise direction provides less total pressure loss than a straight diffuser. The bleed system employed upstream of the inlet is effective for the suppression of the total pressure loss. The diffuser performance depends strongly on the Mach number gradient, since it is sensitive to the flow separation due to large Mach number gradient.

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The unsteady starting process of an axisymmetric hypersonic nozzle in a conventional reflected-type shock tunnel has been simulated with an inviscid flow model using an upwind TVD scheme. In addition, the bursting process of a secondary diaphragm mounted at the shock tube end wall has been numerically reproduced in a time-accurate manner. The effects of initial nozzle pressure and incident shock strength on the nozzle starting time and propagation behavior of shock wave systems have been investigated. The results show a formation mechanism of a rearward-facing secondary shock wave and the behavior of shock waves and contact surface propagating in a convergent-divergent nozzle. Some of the results indicate that the shape distortion of a secondary shock wave severely delays the establishment of a quasi-steady flow under certain calculation conditions.

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In this paper, the interaction of the reflected shock wave with the boundary layer in a duct was numerically investigated in order to clarify the mechanism of the production and growth of shock bifurcation during interaction. Computations were carried out by solving the two-dimensional and compressible Navier-Stokes equations by using the total variation diminishing (TVD) scheme. Calculations were performed for three kinds of gases in the cases wherein the strength of the shock waves, the flow Mach number and the temperature of the wall are different based on the assumption that the heat transfer exists only slightly at the wall. the numerical results were numerically visualized by the contour lines of pressure, Mach number, the vorticity, sonic lines, velocity vectors, pressure distributions and wave diagrams, and the effects of preceding parameters on the interaction as well as the relationship between the growth of the shock bifurcation and the development of the separation of the boundary layer were clarified.

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The present paper reports the experimental and theoretical results for oblique reflection of weak shock waves. We introduce a modified three-shock theory to explain the well-known von Neumann paradox for weak Mach reflection. The theory proposed here considers the effect of slipstream divergence immediate behind a triple point. By giving the angle of slipstream divergence parametrically, we obtain some characteristics, such as the angle of reflection, around the triple point. We compare the numerical results thus obtained with experimental results. For weak Mach reflection, the modified three-shock theory gives physically realistic solutions, even when the von Neumann's classical three-shock theory has no solution. All the experimental data exist in the domain given by the present theory.

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The unsteady boundary layer induced by propagating compression wave has been investigated by means of a recently developed laser differential interferometry (LDI) method using Wollaston prisms. The difference of the two detector signals in LDI will therefore be essentially free of vibrations and laser output variations. LDI can be made more sensitive to optical path changes by 2 to 3 orders of magnitude than in classical interferometry. The sensitivity was sufficiently high to record the density variations by compression waves. The measurements of the time-dependent profiles gave detailed information on the process of formation of the unsteady boundary layer induced by propagating compression wave in a constant-area duct. It was found that the laminar-to-turbulent transition in unsteady boundary layer flow, which describes the density profiles at a strength of the initial compression wave from 9 kPa, exists.

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An experimental study is carried out on the emission of a propagating compression wave from an open end of a tube. A shock tube with a fast opening gate valve instead of a diaphragm is employed for producing compression waves of various strengths. The magnitude of the impulsive wave emitted from the open end is compared with the results of aeroacoustic analysis presented in the previous reports. The directivity of the impulsive wave and its attenuation with distance are discussed. It has been shown that the magnitude of the emitted impulsive wave agrees well with the results calculated by the aeroacoustic analysis, and the directivity of the impulsive wave is independent of the strength of the compression wave but depends on the length of the compression wave.

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A compression wave discharged from an open end of a tube causes positive impulsive noise. Active noise cancellation which is the cancelling of the noise by the addition of an inverse wave is a useful technique for reducing impulsive noise. The final objective of this study is to present the design for a negative impulsive wave generator utilizing unsteady mass influx. In this paper, in order to clarify the relationship between the unsteady mass influx and the negative impulsive wave, experimental investigations have been carried out using an unsteady expansion wave discharged from an open end of a shock tube, together with the numerical and aeroacoustic analyses. As a result, the effect of an unsteady expansion wave on a negative impulsive wave was shown, and then a suitable choice of design factors for the generator was discussed.

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An experimental study of shock waves generated by high speed train entry into a tunnel was conducted using a scaled tunnel simulator. The scaled tunnel simulator consisted of a 25-m-long tube of 40 mm diameter and a launcher. A 200-m-long plastic cylinder of 18 mm diameter represented a scaled train model which was launched with velocities ranging from 50 to 120 m/s. The scaled tunnel simulator was tilted 8 degrees from the floor, thereby preventing train model deceleration due to friction between the tube wall and the plastic cylinder. A simple compression wave was generated at the entrance of the tunnel simulator. When the train model velocity was high, the compression wave became a shock wave. The shock wave built up in the tube was visualized by holographic interferometry. It is concluded that the present scaled tunnel simulator is useful for simulating shock wave generation accompanying the increase in train velocity.

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In connection with the reduction of exhaust noise in automobile gasoline engines an experimental investigation was carried out on the initiation and propagation of shock waves in the exhaust gas flow. The pressure measurement along the exhaust gas pipe clearly shows a non linear transition of compression waves into shock waves. In order to obtain direct evidence of shock waves in the exhaust gas pipe, a holographic interfherometric flow visualization study was also conducted. Shock waves of Ms = 1.1 were observed. For the purpose of obtaining data for designing a silencer configuration which can effectively suppress a shock wave, shock tube experiments and numerical simulations were carried out. Resultsindicate that, in the design of silencers, the non linear wave propagation effect should be takeninto account and a double-chamber silencer is preferable.

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In this paper, the shock wave propagating in a rectangular elbow and the transient flow induced by the shock were investigated numerically in order to clarify how the transmitted shock wave past the elbow is stabilized to uniformity by the effects of area reduction and the rounded corner. Computations were carried out by solving the two-dimensional compressible Navier-Stokes equations by using the total variation diminishing (TVD) scheme. Calculations were performed for three kinds of area reduction ratios and the elbow whose outside corner is rounded, and the flow fields were numerically visualized by the contour lines of pressure, vorticity, velocity vectors, sonic lines, pressure distributions and wave diagrams. The numerical results showed that the distance at which the nonuniformity of the transmitted shock continued became shorter with increasing area reduction ratio and the attenuation of the transmitted shock was considerably weak.

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It is important to understand the aerodynamic characteristics of a circuit breaker nozzle with a complicated inner shape. Therefore, the experimental apparatus was fabricated with air instead of SF₆ as the working fluid. Experiments were conducted using an acrylic nozzle model and a glass nozzle. The flow visualization of flow in the acrylic nozzle model was conducted using the laser light sheet technique, and the flow visualization of flow in the glass nozzle model was conducted using the laser shadowgraph method. Moreover, the flow velocity in the glass nozzle model was measured using a laser velocimeter. Judging from the experimental results, the weak shock is formed in front of the electrode in the circuit breaker nozzle.

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Experimental studies on the interaction between a shock wave and a low-porosity foam are conducted by using a shock tube 125 mm in inner diameter and 10080 mm in length. The density of the experimental polyurethane foam is 284 kg/m³. Stress-strain relationships of the foam are investigated experimentally. The purpose is to investigate the effect of the impact of the gas dynamic shock wave on the unsteady deformation of the foam. One end of the foam is fixed to the end wall of the shock tube, and the shock tube flow is initiated by the quick acting valve. Experiments are conducted in the shock tube for incident shock Mach numbers of 1.7 and 1.9. Experimental time histories of the surface stress of the foam at the end of the shock tube show damping vibrations approaching the gas dynamic pressure of the reflected shock wave, and the peak stresses amount to several times the pressure of the reflected shock wave.

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Numerical simulations of the one dimensional unsteady motion of low-porosity foam, induced by the shock wave are studied. Interactive motions of the gas and the foam are analyzed using the Lagrangian coordinates. An elastic model for a low-porosity foam is assumed to be a simple non linear elastic body following the measured stress-strain relation of foam. One end of the foam in the axial x-direction is fixed to the end wall of the shock tube, and the other end interacts with the shock wave. In the case of uni-axial stress loading, the movement of the body is free to expand in both the y-and z-directions. In the case of uni-axial strain loading, there is no movement of the foam in the y-and z-directions. Results for the foam are compared with those for the rubber. Very good agreements are found between numerical and experimental results in the case of rubber, while fairly good agreements in the case of polyurethane foam.

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Flow of double coaxial pipe jets has been experimentally and numerically studied. Utilizing the tandem-type hot-wire technique and smoke-wire technique, the present investigation confirms the existence of recirculating cells around the axis of circular coaxial jets when the velocity ratio of inner jet to outer jet is small. It is found that the cells expand when the velocity ratio decreases and the outer pipe length increases. Quantitative agreement is found between the hot-wire mean velocity measurements and the numerical calculations by the standard k-ε model along the jet axis in the presence of cells. Several nozzles with outer pipe lengths of L/D₀=0 to 2 are employed to examine interaction of inner and outer vortices. It is found that the correlation of velocity fluctuations between the inner and outer mixing regions increases markedly when the outer pipe lengths are L/D₀=0.5 to 1. The measured distributions of phase-average velocity perturbation and vorticity show the coherent structures in the inner and outer mixing regions of the jets.

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Mean and fluctuating velocities have been measured for a two-dimensional gas jet impinging on a solid concave surface. Measurements are made by the technique of rotating a probe with an inclined hot wire under the Reynolds number of 16500. The figures are shown for distributions of the mean velocity, the turbulence energy and the Reynolds stress. And the influence of the curvature of the wall is found evidently in these jet characteristics. Also, the static pressure in the jet and on the surface is calculated by using the measured results of velocities, and the validity of the calculating method is confirmed by comparison with the experimental results.

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For a notchback model, the time-averaged wake pattern basically consists of the arch vortex behind the rear window and the trailing vortices behind the trunk deck. However, the unsteady characteristics of these wake patterns have not been clarified yet. In this study, we attempted to analyze the unsteady wake structure using flow visualization and measuring velocity fluctuation. As a result, it was found that the critical geometries which increase the aerodynamic drag have the L-type vortex behind the rear window. The L-type vortices intermittently occur at the right-side or left-side rear window and are swept out. (The time-averaged pattern of the L-type vortices is similar to the arch vortex.) It was clarified that the L-type vortex is related to the aerodynamic drag.

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Turbulence characteristics of the supersonic turbulent mixing layer were investigated using a two-component LDV. The high-speed stream was of Mach number M₁= 2.24 and low-speed one was of M₂=1.61 (convective Mach number M_c=0.18, and free-stream velocity ratio r=0.86). To examine the behavior of fluid entrained into the mixing layer, single-stream seeding experiments were conducted ; either a high-speed stream or low-speed one was seeded. In the fully developed regions of the mixing layer, it was found that the mean streamwise velocity of fluid within the mixing layer, which originated from the high-speed stream, was not equal to that of the fluid from the low-speed stream. The transverse locations in which the turbulence intensity and Reynolds stress showed maximum values for the high-speed-stream seeding case was not coincident with that of the low-speed seeding case. They were also compared with that of the incompressible mixing layer case. The growth rate of the mixing layer was almost same as that of the incompressible case. The mixing length based on Prandtl's mixing length hypothesis was also discussed.

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An experimental study was carried out on a fully developed turbulent channel flow with uniform injection through a porous wall at five injection rates. The turbulence intensities of velocity fluctuations and Reynolds shear stress were measured by means of a hot-wire anemometer. The statistical properties, i. e., power spectrum, probability density function and skewness/flatness factors, were investigated. Turbulence intensities and Reynolds shear stress increase with increasing injection rate. The correlation coefficient depends slightly on injection rate and is constant across the channel. The skewness factor increases with increasing injection rate in the near-wall region. The result reveals that sweep motion is strengthened by injection.

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The results of direct numerical simulations are presented for turbulent mixing layers with chemical reactions using the higher-order method of lines. The reaction considered is a binary, single-step, irreversible reaction without heat release, so that the chemical reaction only depends on the flow field. We consider two cases, i. e., roll-up and pairing. In the roll-up case, the product field is similar to the flow field. In the pairing case, the product and the flow fields show similar behavior as in the roll-up case before the roll-up process. After that, the braid region is shown clearly in the product field, in comparison with the flow field. The chemical product is produced in the braid region and around the core region, and is concentrated in the core region.

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Fluid dynamical interactions between liquid and a solid particle have been experimentally clarified in isotropic turbulence generated by a grid in a gravitational flow. Particles with mean diameters of 180 μm and 476 μm were loaded into the flow with U_p0=0.4 m/s, 0.7 m/s and 1.5 m/s at the center point of the test section well downstream of the grid so that the turbulence was steady and locally isotropic. A laser-Doppler velocimeter capable of particle size discrimination was employed for detailed measurement of particle and liquid velocities and particle number density. The results show that particle motions become nonisotropic due to gravity. Momentum transport between particles and turbulent motion is absent due to the nonisotropic particle motion and the relative velocity between particle and fluid. The eddy diffusivity ratios between particle and fluid are well correlated by the Stokes number which is calculated from the Kolmogorov time scale at the inlet position and the particle relaxation time. It is pointed out from the results that the interaction between particle and turbulence motion at the initial point governs the particle dispersion in the grid turbulence. In the grid turbulence, overshoot phenomena do not occur, and therefore, the maximum value of the diffusivity ratio is approximately equal to unity.

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Two-phase flow dynamics plays an important role in the understanding of the kinetics of unclear reactors and boilers. Difficulties has been reported in obtaining the numerical solution of two-phase flow by the two-fluid model which was described as basically ill-posed. Our previous paper described the behavior of the numerical solution of the heat-conduction equation under the ill-posed condition. In the present paper we show the effect of the convection term of the advection-diffusion equation under the ill-posed condition. The present study serves as an alternative to understanding the ill-posedness of the two-fluid model.

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An adaptive fuzzy reasoning strategy was studied to obtain fast convergence for a 2D incompressible Navier-Stokes solver. In this study, this reasoning was applied to control of the relaxation factor when the Poisson equation was solved by the point SOR method. Normalized residual and relaxation factors themselves were used for input parameters to the control map or lookup table. Several maps optimized for different flow conditions were prepared, and selected almost randomly. This map-selecting strategy made it possible for the flow solver to carry out fast and stable calculation. Two-dimensional thermal convection was used to examine the effectiveness of this scheme, and the solutions obtained with and without adaptive control were nearly equal.

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In the first report, the dividing flow properties of Newtonian fluid in two-dimensional steady laminar flow were presented. In this report, the flow patterns and the enrgy losses of the viscoelastic fluid (separan solution) are shown. In the dividing flow of the separan solution, two separation zones were also observed, as in those of Newtonian fluid. However, the sizes of the separation zones of the viscoelastic fluid are smaller than those of Newtonian fluid. Also, swelling of the streamline to the main conduit or to the lateral conduit was observed, which was not observed for Newtonian fluid. The loss coefficients of the viscoelastic fluid are larger than those of Newtonian fluid. The loss coefficients for the lateral conduit increase as the cross-sectional area of the lateral conduit is reduced, but the loss coefficients for the main conduit do not change grately.

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The Space-Time Galerkin method provides a framework for solving fluid-structure interaction problems #(FSI). These formulations allow us to use different fluid meshes for each time-slab. The space-time elements can be oriented in time, thus accommodating spatial deformation. The mesh generator between time slabs and adaptive mesh rezoning techniques within each time-slab play important roles in FSI problems. We have developed an adaptive mesh rezoning technique with the least-square constrained conditions, which prevents the element located close to the moving boundary from breakdown trouble and maintains its well-conditioned shape. The technique is entirely general in that it can be effectively applied to structured and unstructured meshes.

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In the surface finishing line of cold steel, many surface defects are caused by contact between the roll support and strip. An optimal suface finishing process should support the strip without contact by roll since high quality steel products depend on stable operation of the running strip. In the two-dimensional flow configuration, our experimental study focuses on stability improvement of the running strip derived from the side plates installed on the pad which has nozzles with a distance much shorter than conventional setup. This study has clarified that the side plates produce the restoring force. That is, if the strip deflects from the central position, the pressure on the deflected side of the strip increases. This pressure causes the floating height of strip on the deflected side to increase. As a result, the strip tends to return to the central position by itself. Besides, it is clarified that the restoring force increases as the distance between nozzles N_b decreases, as a result of an increase in the area of pressure P_p, caused by the side plates. This is contrary to the conventional method without side plate where large lifting and restoring forces are created with a large nozzle distance N_b.

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A numerical simulation for axial and swirling flow pneumatic conveying in a horizontal pipe is carried out with an Eulerian approach for the gas and a stochastic Lagrangian approach for particles, where particle-particle and particle-wall collisions are taken into consideration. The k-ε turbulence model is used to characterize the time and length scales of the gas-phase tubulence. Models are proposed for predicting the particle source and additional pressure loss. The numerical results are presented for polyethylene pellets of 3.1 mm diameter conveyed through a pipeline of 13 m in length with an inner diameter of 80 mm. It is found that numerical results agree with our measurements.

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The feasibility of a detailed numerical simulation of a Taylor bubble in a stagnant liquid filling in a vertical pipe was examined in the present study. The simulation was carried out using the volume of fluid method. Since there have been few quantitative experiments on Taylor bubble shape, physical experiments under a wide range of the Eotvos number (Eo) and Morton number (M) were also conducted using sucrose solution and air at room temperature and atmospheric pressure. It was confirmed by the experiments that the bluntness of the nose of the bubble, the flatness of the tail, and the liquid film thickness around the bubble are strongly affected by the two dimensionless numbers, Eo and M. Calculated terminal rising velocities and bubble shapes agreed fairly well with the measured ones, which indicates that the effects of drag force, buoyancy and surface tension force on the bubble were well predicted in the simulation.

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It has been shown that the premixed abrasive water jet system has a greater capacity for drilling and cutting than the conventional abrasive water jet system. In the present investigation, the motion of spherical particles in a premixed abrasive water jet nozzle is investigated theoretically. The flow in the nozzle is treated as one-dimensional flow. Convergent nozzles with and without a cylindrical focusing section are studied. The numerical results show that the particle velocity at the outlet of the nozzle has a tendency to increase in proportion to the square root of the injection pressure. The outlet particle velocity decreases with increasing diameter and specific gravity of the particles. The optimum length of the focusing section increases with increasing diameter and specific gravity of the particles.

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In one of the proposals for a cut-off classifier, an injection port is mounted at the collecting mouth, and sand (relatively large particles) and muddy deposits (relatively small particles) which are deposited under a body of water are fluidized before the particles are collected. Thus only the small particles are lifted, and their transport can be made more effective and smooth by controlling the velocity at the entrance of the suction unit. The maximum diameter of the particles lifted is determined only by the suction velocity of water. It was clarified from the results of flow visualization in the vicinity of the collection region that good separations are achieved for several combinations of spherical glass beads. By analyzing the image of the visualized region, the effects of the injection on the cleaned volume and the effect of small bead diameter on the collection time could be discussed quantitatively.

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The draft tube of a cross-flow turbine uses the difference in level between runner and tail water, especially in the case of low heads, We intented to obtain the desirable profile of a draft tube of a cross-flow turbine and present the effects of water level in the draft tube on the turbine performance. The main results are as follows. (1) The flow velocity in the draft tube is high near both side walls and low at the central part, because the flow which is directed radially outward at the runner exit is restrained by both side walls of the draft tube. (2) In the case of underwater operation of the runner, the vortex flow accompanying the re-entry flow to the runner must be prevented. (3) The optimum ratio of the width of draft tube to the length of nozzle exit arc is nearly 1.6.

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Model tests were carried out for an ultralow-head hydropower system, consisting of a two dimensional ducted water turbine of Darrieus-type and an electric generator. Self-starting and moving processes from rest to any operating point were investigated experimentally under various loading conditions for the generator. In the present study these processes are simulated numerically by solving one-dimensional equations which govern the hydropower system, using evaluated steady characteristics of the runner and the generator. The matching problem of both characteristics is discussed for higher system efficiency. A control method with a sluice valve to keep the operating condition constant is examined tentatively by numerical simulation.

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Local heat transfer and pressure drop measurements were made during condensation of a nonazeotropic refrigerant mixture R114/R113 in the annulus of a double-tube coil consisting of four straight sections and three U-bends. The inner tube was a corrugated tube having soldered wire fins. The vapor phase mass transfer coefficient exhibited a sawtooth behavior, with those of the U-bends larger than those of the straight sections. The frictional pressure gradient data agreed well with a previously developed empirical equation for the condensation of pure refrigerants. A prediction method for the condensation heat transfer rate was proposed on the basis of the correlations of the vapor phase mass transfer coefficient and heat transfer coefficient of the condensate film. The heat transfer data were correlated by the present prediction method to a mean absolute deviation of 12.9%.

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In order to enhance the condensation heat transfer of binary vapors of immiscible liquids, detailed experiments have been conducted with regard to the condensation of an azeotropic mixiture of carbon tetrachloride and water on horizontal tubes with enhanced fins. The condensation mechanism of this kind of vapor on horizontal tubes is clarified through the measurement of droplet departure frequency and heat transfer rates. The experimental results indicate that finned tubes are more effective in the enhancement of condensation heat transfer of binary vapors of immiscible liquids, and that an optimum dimension of fins exists.

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Experiments using a wind tunnel were conducted to clarify the distribution of the local heat transfer coefficient in a pin-fin array. Pin-fin test cores were constructed of pin rows arranged regularly in the flow direction. A local heating method was utilized to measure the heat transfer performace. Pin rows were heated through direct application of an electric current, and their individual temperatures were determined by measuring the electric resistance. Measurements were carried out under two conditions : when the individual pin rows in the pin-fin array were heated separately, and when all the pin rows were heated simultaneously in a uniform heat flux. The range of the Reynolds number tested was 20-100. Flow visualization experiments were also carried out to observe the flow pattern in the pin arrays utilizing a fifteen-times-enlarged model and a water tunnel. The test results revealed the heat transfer performance of the fins, and the effects of an oscillating flow on the heat transfer mechanism are discussed.

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In this study, the melting prosess of ice containing heat-conductive solids such as a copper lattice metal or a porous aluminum is investigated by measuring the melting rate, the heat flux flowing into ice and the temperature distribution of melted water. Experiments were performed for four melting modes, namely, (A) melting from top and (B) melting from bottom by brine at about 20°C, and (C)melting from top and (D) melting from bottom by brine at about 40°C. In the case of lattice metal, the melting process was affected by the natural convection for modes (A), (B) and (C) because the lattice size was large, but it was nearly unaffected in the case of mode (D). In the case of porous aluminum, natural convection was not observed for any of the melting modes in the present experiment because the cell size was small and the melting process was extremely dependent on heat conduction.

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Deterioration in heat transfer to supercritical water is numerically studied using a k-ε model. Physical properties are treated as variables and calculatd from the steam table library. The numerical result agrees with the experimental data of Yamagata et al. [Trans. JSME, 38-2(1972)]It is found that heat-transfer deterioration is caused by two mechanisms depending on the flow rate. In the case of large flow rate, heat transfer is reduced near the wall where the fluid properties are locally changed due to the heat flux. In the case of small flow rate, buoyancy force flattens the flow velocity distribution and the turbulent heat transfer is decreased. The present analysis shows that supercritical thermal hydraulics can be explained by the single-phase turbulent fluid dynamics.

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In order to provide better cooling performance for transformer windings which use nonflammable coolant, conductors wound with thread spacers were applied to the windings to enlarge the cooling surface area. It was necessary to clarify the effects of the spacer diameter and different kinds of coolant on flow and cooling characteristics in the windings. Using two two-dimensional winding models, pressure drop in the windings and temperature rise of the conductors were measured for perfluorocarbon liquid and air. The two winding models consisted of model conductors in which thin heater pins and thermocouples were soldered together and wrapped in insulating paper. The conductors were also wound with two thread spacers having different diameters, 0.75mm and 0.5mm. The common frictional resistance and the heat transfer coefficient for perfluorocarbon liquid and air in vertical ducts between the conductors were derived for laminar and turbulent flow, respectively. The temperature rises for the thread spacer windings cooled by SF₆ gas were predicted as being signficantly lower than those in baffle plate windings for commercial transformers with the same pressure drop in the windings.

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A numerical analysis for natural convection heat transfer in eccentric cylindrical annuli was presented. This problem is one of the most basic problems for a shell and tube-type heat exchanger. Many studies on heat transfer in eccentric cylindrical annuli on the view of flow pattern have been done, however, only a few studies on the effect of eccentricity on heat transfer enhancement have been conducted. The numerical method presented in this paper utilized the boundary-fixing method which is applicable to the moving boundary problem. Calculations are made for isotherms, streamlines, dimensionless Nusselt number distribution around the cylinder, and dimensionless total heat transfer. The effects of eccentricity on heat transfer enhancement and convection mechanism in eccentric cylindrical annuli are presented.

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A systematic measurement is conducted for heat transfer and pressure drop performances of the flow through the wire-fin heat exchangers which consist of closely packed thin wire arrays. The nine wire-fin cores which are constructed by systematically varying the transverse and longitudinal fin pitches are tested in the present study. A Modified single-blow transient test method is applied to evaluate the performances. Two distinct heat transfer behaviors are observed in the range of Reynolds number between 20 and 200. They are : (1) steady laminar flow heat transfer and (2) turbulent flow dominated heat transfer. An empirical expression for the critical Reynolds number is presented in terms of the geometrical parameters of the wire arrays. The empirical correlations for the heat transfer performances in the laminar flow region are also pressented as a function of the geometrical parameters as well as the Reynolds number.

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A specially designed grating is applicable to directional control of radiation heat transfer from a heated surface. In this paper, a study of radiation heat transfer control using a grating composed of elliptical cylinders (GEC) is described. An analysis of radiation heat transfer is performed for a physical model in which the grating of circular cylinders (GCC) of our previous study are replaced by the GEC and the major or minor axes of the elliptical cylinders are set vertically to the heated base surface. Numerical solutions are obtained. The apparent hemispherical emissivity and the limiting angle expressing the degree of radiation energy concentration are calculated for geometrical parameters, e. g., ratio of the major axis to the minor axis and center-to-center distance of cylinders. It is found that the GEC has even better characteristics for the control of radiation heat transfer, compared with the GCC, especially for apparent hemispherical emissivity, i. e., the heat-transfer rate.

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This paper shows how the heat-transfer coefficients along heated tubes are affected by the clearance against the tube wall, the inlet angle and the widths of various types of blade wheels which are propelled by an internal flow in a circular tube and inserted at the inlet in order to augment heat transfer along the tube. The maximum and averaged heat-transfer coefficients in the region from blade position to far downstream were 3.0 and 2.2 times those in smooth duct respectively, for air ranging in Reynolds number from 15000 to 60000. Moreover, the performance evaluation was carrid out under the condition of fixed pumping power, and it was found that the performace ratio depends more on the inlet angle and the width of the blde than clearence, and the ratio is larger than one.

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The enhancement of longitudinal heat transfer by means of fluid pulsation in a circular pipe with heat loss through the pipe wall has been investigated. An analytical solution is obtained for the case that heat loss through the pipe wall during one cycle of fluid pulsation is uniform along the pipe. Based on the analytical solution, some characteristics of the phenomenon are discussed. These include the effect of heat loss on longitudinal heat transfer and temperature distributions, as well as the effect of pulsation frequency on the amplitude of temperature pulsation.

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Carbon-carbon composites are important structural materials for high-temperature environments. Their thermal properties and microscopic structures change with the temperature and the time required for heat treatment. It is expected that the thermal diffusivity and porosity will show different values at every moment during heat treatment. The objective of this study is to evaluate the time dependence of the thermal diffusivity and porosity simultaneously using the electromagnetic ultrasonic technique. This report describes the thermal diffusivity measurement of type 304 stainless steel and a two-dimensional weave carbon-carbon composite at room temperature, and the analyses of the eddy current and heat conduction to clarify the influence of the distribution of induction heating for thermal diffusivity measurement.

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The confined jet of two-phase mist flow is important for the development of a two-phase ejector in refrigeration cycle. However, the flow characteristics of the two-phase ejector have not been elucidated to date due to the nonequilibrium of velocity and temperature. In this study, the mixing characteristics of two-phase mist flow in the two-phase ejector were investigated experimentally. The pressure rise in the mixing section and the diffuser of the ejector was measured. The following results were obtained by comparison of the measured pressure rise with that calculated using a simple theory. The increment of the length and the decrement of the diameter of the mixing section were effective for raising the pressure. The energy efficiency of the two-phase ejector used in this experiment was approximately 10%. This efficiency is expected to be increased by the improvement of the mixing characteristics of the ejector and the nozzle efficiency.

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An experimental study has been conducted on air-water two-phase flows in a flat channel with a sharp 180-degree turn which simulates the refrigerant channel of an evaporator for an automobile air-conditioning system. Attention has been directed to the influences of channel attitudes on two phase flow characteristics such as local void fraction and pressure drop. Five channel attitudes have been tested here ; [U] : The channel is set vertically in the shape of a "U". [RU] : Upside-down of [U]. [TF] : The channel is set in the shape of a "C" and fluids are fed from the upper entrance. [BF] : Fluids are fed from the lower entrance of the "C"-shape channel attitude. [H] : The channel is set horizontally. Uniform liquid film flow, which is favorable in the heat-transfer performance of the evaporator, is obtained in the channel attitudes of [RU] and [H]. The pressure loss is higher in [U] and [BF] under the condition of low quality. Irrespective of the channel attitudes, the pressure loss in the present test channel can be well expressed by the modified Lockhart-Martinelli correlation. From the results of the experiments, it has been found that the channel attitude of [RU] is the most favorable for the evaporator refrigerant channel.

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The mechanism of countercurrent flow limitation (CCFL) was investigated analytically and quantitatively for the existing experimental results for vertical circular tubes, adopting a criterion that the CCFL condition is given by maximizing falling water mass velocity with respect to void fraction for the whole flow channel. Through the analysis, it was found that significant factors in the CCFL condition were the interfacial friction factor between liquid and gas based on the relative velocity, wall friction factors for laminar, transition and turbulent liquid flows and the effects of tube diameter and length. Analytical results gave very good predictions of the experimental results for vertical circular tubes of 19 to 140mm in diameter and 12.7 to 1520mm in length, under atmospheric pressure.

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Expansion of passive safety function is proposed. Two notions are presented. One is that in the design of passive safety nuclear reactors where aversion of active components is stressed, some active components are purposely introduced, through which a system is so built as to behave in an apparently passive manner. The second notion is that instead of using passive safety function in its sole way, passive safety function is combined with some active components, leaving the passivity in safety action with the enhanced controllability in normal operation. "Non-Dormant System" which we propose is one example to the former. In this system, standby safety system is turned portion of the normal operation system let worked non-dormantly. Interpretation to Non-Dormant System via Synergetics-wise viewpoint is made. As an example to the latter, PIUS Density Lock aided with active components is proposed and is discussed.

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