A drag coefficient, C_D, of a single bubble in an infinite stagnant liquid is the basis for developing a constitutive equation of interfacial drag force. Up to the present, the interfacial drag force has been, however, often evaluated using CD of a rigid particle, which is valid only for a spherical bubble in a contaminated liquid. Hence, a simple but reliable constitutive equation of CD was proposed in the present study. The proposed CD consists of three equations, each of which corresponds to pure, slightly contaminated and contaminated systems. Terminal rising velocities of bubbles were calculated using the proposed CD, and compared with the measured data under the conditions of 10^-2 < Eo < 10³, 10^-14 < M< 10⁷ and 10^-3 < Re < 10⁵ where Eo, M and Re are Eotvos, Morton and Reynolds numbers. As a result, it was confirmed that the proposed CD gives better predictions than available constitutive equations.

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The flow of superfluid helium (helium II) above a critical velocity enters a turbulent state with a dense tangle of quantized vortices. Although very little is known about the mechanism of the transition, it is widely accepted that the transition is influenced by the roughness of the boundary surface. Thus in this paper, we numerically study three-dimensional dynamics of interactive quantized vortices near a pinning site under an applied flow in order to investigate the effect of the surface roughness. First, the conditions under which vortices are attracted to a pinning site are discussed. Secondly, we discuss the finite capacity of a pinning site, and the critical depinning velocity for pinned vortices. Thirdly, the critical depinning velocity under thermal counterflow is compared with some experimental results, and the agreement is found to be very good.

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This paper presents an experimental study of the air-water bubby two-phase flow in a U-tube (bent at 180 degrees) . The bubble interfacial configurations were measured using the image-processing method. The diameter and the position of the bubbles in the tube cross section were at right angles to each other. The measurements revealed that the bubbly flow travelled near the inside wall of the bent tube due to centrifugal force. The relative high secondary flow from towards the outside wall of the bent tube separated the bubbles from the inside wall of the tube at the top the bend, i. e., at the 90-degree point. Bubble elongation in the tube diametric direction was shown at bends of 90-180 degrees.

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Large-eddy structure of a d-type rough wall boundary layer manipulated with longitudinal thin ribs placed within transverse grooves has been investigated experimentally in terms of a dynamical equation for a two-point velocity correlation function, U_AU_B. Two-point triple velocity correlation functions involved in diffusion terms were measured in order to obtain spatial structure and the scales of three-dimensional vortical motions. It is seen that a pair of streamwise vortices with low-speed common-up flow is the primary structure. The spanwise stretching motion and interaction with high-speed sweeps from the outer layer make a dominant contribution to energy transfer from the large-scale eddy to smaller-scale one. The longitudinal thin ribs restrict the spanwise stretching motion and low-speed common-up flow and then reduce the strength of streamwise vortices which also make a dominant contribution to the turbulent production. The effect of wall modification with the longitudinal thin ribs can be found in the large-scale structure in the outer layer.

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An analysis method has been developed for the prediction of flow in a cross-flow fan with a casing. The method has no simplifying assumptions regarding the geometry of either the impeller blades or the casing. Taking into consideration the effect of the boundary layer on the upper wall surface of the casing, the internal flow is analyzed using both the boundary element method and the discrete vortex method by assuming that the flow is two-dimensional, inviscid and incompressible. In order to satisfy Kelvin's theorem, vortices are shed at the trailing edges of each impeller blade. The discrete vortex method is used to approximate the convection of the free vortices. Results are given for the cross-flow fan with two different configurations of the casing with an identical impeller.

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The present study has carried out a numerical analysis for developing turbulent flow in a square-sectioned 90 deg bend at Reynolds number of 4×10⁴. The ratio of bend mean radius of curvature to hydraulic diameter is 2.3, and straight ducts of 45 and 30 hydraulic diameters long are attached to the inlet and outlet planes of the bend, respectively. In calculation, an algebraic Reynolds stress model was adopted in order to predict anisotropic turbulence precisely, and the boundary-fitted coordinate system was introduced as the method of coordinate transformation. Calculated results were compared with the experimental data measured separately by two research groups. Moreover, the transitions from the secondary flow of the second kind to that of the first kind and vice versa are examined. It was found that the present method predicted well the distributions of mean flow velocity and pressure-driven seconary flows. In the straight duct of the bend outlet, the secondary flow of the first kind maintains its value until about 1.0 hydraulic diameter from the bend outlet. After remaining constant in value up to this point, the secondary flow decays and gradually transforms to the secondary flow of the second kind at the about 10 hydraulic diameters from the bend outlet.

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Our aim here is to construct a data base of flow which is neither as complicated as backward step flow nor as simple as flat channel flow, for the purpose of fabricating new improved turbulence models. A direct numerical simulation was conducted for turbulent channel flow with periodic pressure gradient, i. e., a channel having a flat plate wall on one side and a wavy one on the other side. The wavy wall, or a sinusoidally indented wall is mimicked by a porous flat wall which allows surface injection/suction of varying strengths. Mean flow field together with statistical quantities of turbulence, such as fluctuation velocities and Reynolds stresses are calculated as a data base. A discussion on the property of the influence of pressure gradient on the flow is presented with reference to our previously published experiments. The budget of transport equations of turbulent stresses are examined.

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Time histories of longitudinal velocity fluctuations in the intermediate and far regions of the turbulent wake of a two-dimensional circular cylinder are analyzed by the wavelet transform employing the antisymmetric, Mexican-hat and Morlet wavelets. Contours of the wavelet transform in the (a, b) parameter space, where a is the scale and b is the temporal location of the center of the wavelet, are found to be basically similar for the three wavelets if the a-and b-axes are properly translated. This is particularly true for the Mexican-hat wavelet and the real part of the Morlet wavelet, both of which are symmetric with respect to the location b. The contours demonstrate the periodic velocity fluctuation associated with the Karman vortex street in the intermediate wake, the low-frequency modulation of the vortices in the vortex street, and the multi-scale structure in the far wake. The Morlet wavelet yields the most detailed multi-scale structure of the velocity fluctuations among the three wavelets.

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The characteristics of turbulence in the boundary layer developed on a rotating cone in an axial uniform stream are investigated experimentally. Measurements of all the six components of the Reynolds stress and the triple products of the turbulent velocity fluctuations are made at various values of the surface-to-free stream velocity ratio λ_b for two different vertex angles, θ=15°and 30°. As λb increases, the destabilizing effect of the centrifugal force becomes stronger, leading to the formation of regular large-scale vortices. The structural change of turbulence caused by these vortices affects the distribution of the statistical turbulence quantities significantly. In the outer region, the direction of the shear stress vector does not align with that of the velocity gradient vector. The ratio of the integral lengh scale to the Taylor microscale, L/λ, increases as the destabilizing centrifugal effect increases.

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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 was obtained by passage through a contracted region. Wall shear stress, mean velocity profile and turbulence intensity measurements following the removal of rapid pressure change were performed using a Preston tube and a hot-wire anemometer. In the near-wall region, an equilibrium state was achieved quickly and the universal law of the wall was maintained, except quite close to the contracted region. On the other hand, the flow in the core region was significantly perturbed and the return of the flow to an equilibrium state was not achieved, even at a downstream distance of 30 channel heights.

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An experimental study has been performed on the mean flow and turbulence properties of a two-dimensional jet impinging on a wedge having a circular cylinder with various diameters at the wedge vertex. The nondimensional profiles of the mean velocity in the fully developed flow region of the wall jet approach those of the conventional two-dimensional wall jet when a cylinder is attached to the wedge vertex and if the cylinder diameter is increased. Also both the slopes of the growth of the half-width and of the decay of the maximum velocity approach these of the two-dimensional case. The non-dimensional profiles of the turbulence intensities and of Rexnolds stress in the fully developed flow region of the wall jet behave in the same manner, as mentioned above. In the variations along the wall of the integral value of the total production term of Reynolds stress, there exists the negative value region of it near the wedge vertex, and it extends as the cylinder diameter increases.

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An experimental investigation was made of the pulsating entry flow in curved pipes (curvature ratios of 10 and 30) with fully developed straight profiles. The experiments were conducted on five flow cases under the conditions of the Womersley numbers α=5. 5∼18, the mean Dean numbers D=200, 300 and the flow rate ratios η=0.5 and 1. The instantaneous axial velocity distributions were measured by a laser doppler velocimeter at several axial locations from the upper stream tangent to the downstream in the curved pipe. The effects of the nondimensional parameters of α, D, η and R_c on the flow development are made clear. The velocity distributions change rapidly with the phase at Ω=15∼30°around the curved turn. The flow phenomena occurring in the entrance region of the curved pipes are too complicated for an intermediate Womersley number α=10. The flow reversal occurs in the inner half cross-section of the curved pipe, Ω≥15°, during the phase of a minimum flow rate for all values of α. The depression in the axial velocity profile appears after the fourth round in the curved pipe for α=10. The inlet length of pulsating flow is less than that of steady flow with the same flow rate as the maximum one in pulsating flow.

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Rarefied gas flows through circular tubes with finite lengths were simulated by the direct simulation Monte Carlo method. The effects of Knudsen numbers, length ratios, accommodation coefficients on solid surfaces, and temperature ratios on transmission probabilities are discussed. The numerical simulation for long-length tubes should be revised for reducing computational time.

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Two-dimensional tumbling behavior is investigated numerically by calculating inlet flows of a tumbling-type nematic liquid crystal between parallel plates. Calculations are performed for various Ericksen numbers. At the comparatively small Ericksen number of Eγ = 10, the director in the upper half space of the channel rotates counter-clockwise before reaching the fully developed value. At Eγ=50, the director shows an abrupt rotation just after the inlet section. The rotation is not only convected to the downstream area but propagated from the region near the channel wall where shear rate is large to the center region. When Eγ is increased further to 100, the director profile does not indicate a monotonic development but a two-step one. In this case, the velocity profile in the main flow direction is wavelike. It is found that the effect of director orientation is strongly reflected on the velocity field, while the reverse effect is weak.

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Simulations are performed for reflection of shock waves at an end wall in noncondensable and condensable gases in a shock tube by numerically solving the Navier-Stokes equations subject to the appropriate boundary conditions using the explicit TVD scheme. Numerical solutions obtained here are compared with those of the Boltzmann equation of BGK type. Good qualitative agreements are obtained between the two solutions for both noncondensable and condensable cases. Hence, the Navier-Stokes equations with the appropriate boundary conditions are shown to be adequate for simulations of gasdynamics phenomena on a scale of the mean free path. Some appreciable discrepancies, however, appear between the numerical solutions of the Navier-Stokes equations and those of the Boltzmann equation as the incident-shock Mach number increase.

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In this paper, the shock wave propagating in an elbow and the transient flow induced by the shock were investigated numerically in order to clarify how the shock wave transmitted past the elbow is stabilized to uniformity by the effects of the elbow angle. Computations were carried out by solving the two-dimensional compressible Navier-Stokes equations using the total variation diminishing (TVD) scheme. Calculations were performed for six elbow angles between 5° to 120°, and the flow fields were numerically visualized by the contour lines of pressure, sonic lines, pressure distributions and wave diagrams. The numerical results showed that the distance for which the nonuniformity of the transmitted shock continued became longer with increasing elbow angle and the attenuation of the transmitted shock was very small.

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An experimental and analytical investigation was made of reflection of shock waves over cones installed in a 60 mm × 150 mm cross sectional diaphragmless shock tube. The diaphragmless shock tube has a high degree of reproducibility with scatter of shock Mach number to be within ±0.25% for shock Mach number ranging from 1.02 to 2.80 in air. Shock Mach numbers tested in this series of experiments were 1.16, 1.20, 1.49, and 2.05. Eighty-six cones whose half apex angles varied from 10° to 52.5° in steps of 0.5° were installed in the shock tube test section and shock propagation over the cones was visualized by double exposure holographic interferometry. A TVD finite difference numerical simulation was carried out, in order to interpret and compare with the experimental results, by solving the Euler equations and an analysis based on Whitham's ray shock theory was also made. It was found that the critical transition angles of the cone were only one or two degrees smaller than those of wedges even though the mode of propagation of the disturbances generated at the leading edge differ between the cones and wedges and that the region in which a von Neumann Mach reflection exists is wider in the case of shock reflection over cones.

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The 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 objective of this study is to present a design for a negative impulsive wave generator utilizing unsteady mass influx. The generator consists of a vacuum chamber and a movable valve. From experimental investigations, the relation between the valve behavior and the characteristics of the negative impulsive wave has been clarified, and a suitable choice of the design factors has been suggested.

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In the first report it was shown, by a linear stability analysis, that a vaneless diffuser rotating stall can be a manifestation of a 2-D inviscid flow instability subjected to vanishing velocity fluctuation at the diffuser inlet and vanishing pressure fluctuation at the diffuser outlet. The purposes of the present paper are to elucidate the nonlinear effects, to determine the factors which set limits on the amplitude of the fluctuation, and to obtain additional information, within the framework of 2-D flow analysis. Two-dimensional nonlinear inviscid and viscous flow calculations are carried out based on the SMAC method. It was found that, (1) the critical flow angle and the propagation velocity determined from the linear analysis agree well with the present calculation, (2) viscosity in 2-D flow, wall friction, and resistance at the diffuser outlet can be the factors that set limits on the amplitude. Reasonable agreements with experiments were obtained, and a discussion is presented as to the energy transfer from steady flow to disturbances.

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This paper describes a detailed study of the flow structure over repeated two-dimensional square ribs on a ground plane for various values of S/D, and the optimum value of S/D to augment the turbulence intensity near the ground plane. The pitch between the centers of two adjoining square ribs was varied at S/D=2, 3, 5, 7, 9, 11, 13 and 17. The time-mean velocity and turbulence intensity were measured by Laser Doppler Velocimeter. The static pressure was measured by Pitot static tubes. As a result, it is concluded that the pitch ratio S/D=9 is optimum to augment the turbulence intensity in the groove between two adjoining square ribs, when the two-dimensional square ribs are aligned on the wall as a heat transfer promoter.

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In the present paper, the natural convections of thermo-electrically conducting fluids in a square cavity under a uniform magnetic field are calculated using GSMAC-FEM in conjunction with the so -called B method. This scheme efficiently satisfies conservation laws of both mass and magnetic flux. In order to establish a stable numerical scheme at low magnetic Reynolds number problems, we introduce both the generalized trapezoidal method and the 3-level fully implicit method into the conventional numerical residual method. The numerical results obtained are in good agreement with the past numerical and experimental results.

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Acoustic streaming is generated by Reynolds stress in the sense of mean acoustic momentum flux in a sound field. In the case of an acoustic standing wave produced by an air column oscillation in a closed duct, the friction and the Reynolds stress in the resulting Stokes layer are the essentials of acoustic streaming generation in the vicinity of the duct wall. The thickness of the Stokes layer decreases with the oscillatory Reynolds number. The plane wave propagation in the duct is assumed for the case of high Reynolds number except for the thin Stokes layer adjacent to the duct wall. The velocity profiles of the streaming are estimated theoretically from the steady component of the second-order term of a perturbation expansion in which the first-order approximation is a sinusoidal oscillation of the air column with plane waves. The present paper describes theoretical analysis of the velocity profiles of the acoustic streaming in the Stokes layer by means of the matched asymptotic expansion method. The results obtained show the existence of reverse streaming in a very thin layer adjacent to the wall and the effects of thermal boundary conditions at the wall on the velocity profiles of acoustic streaming in the Stokes layer.

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Various aspects of unsteady stall flows arising in linear rotor-stator cascades of a single-stage axial compressor are studied numerically by a TVD finite-difference analysis of two-dimensional compressible Navier-Stokes equations. The computational system consists of a rotor and a stator, where the flow is assumed to be periodic over either three blades and five vanes, or six blades and ten vanes, respectively, depending on the scale of vortical structure induced by the rotor motion. Relative motion of the cascades is simulated by sliding the grid fixed to the rotor past the stationary grid fixed to the stator. Although the flow is constrained in a two-dimensional plane, and the analysis is conducted without a turbulence model, computed stage characteristic from high-flow to deep stall is found to be similar with the rig test data. Features of unsteady flowfield under normal operating conditions, as well as typical flow patterns inside propagating stall cells at various load are presented. Computed flow velocity ahead of and behind the rotor under design condition is compared with the measured data. Furthermore, computed force and moment acting on the blades under stalled condition are described. Blade Reynolds number and Mach number are 2.8×10⁵ and 0.3, respectively, to meet the rig test conditions.

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This paper presents an experimental investigation focused on the structure of the horseshoe vortex at the wing/end wall junction. A flat wing has a semicylindrical leading edge and constant body thickness. The wing is set on the end wall with an attack angle. The reference velocity is 16.2m/s, the boundary layer thickness is 22 mm and the Reynolds number based on the radius of curvature of the wing leading edge is 2.4×10⁴. The pressure loss at the down-wash side of the vortex is small, but it takes a large value at the up-wash side. The loss is large at the suction side of the wing. The vortex center shifts from the wing in the downstream direction in the suction side.

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This paper presents the response of vorticity and Reynolds stress transport in the horseshoe vortex at a flat wing/end wall junction. The measurements using the specially designed triple hot-wire anemometer Simultaneously provide three components of mean velocity and six components of Reynolds stress. The horseshoe vortex moves away from the wing/end wall junction by convection and diffusion of the secondary flow. The vortex becomes large because of the diffusion of turbulence. The rotation velocity of the vortex is large at the pressure side of the wing and the vorticity decays due to the stretching mechanism. The location of Reynolds stress, - uv, which takes a negative value does not correspond to the region of the negative mean velocity gradient upstream.

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Flow around a rotating Darrieus turbine was simulated by solving 2-d Navier-Stokes equations. The equations were discretized by the Finite volume method for space and the Fractional step method for time. The convection terms were specially discretized by an upwinding scheme for an unstructured grid. In this report, single-blade and two-blade turbine without the duct were simulated. Values of the parameters were as follows : blade section, NACA 0018 ; and Reynolds number, 3×10⁵. The results showed good agreement with experimental data in the following point : optimum tip speed ratio decreases inversely with solidity. Simulated flows were visualized by stream lines, vorticity, pressure distribution, and streak lines. The visualized flow fields can explain the torque-generating mechanism.

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Present paper aimed to analyze the coupled torsional and bending flluter of a compressor circular cascade composed of main and splitter blades. From the theoretical treatment of the analysis, the unsteady forces and moments of blades carried out a combined motion of torsion and bending are calculated for the main and splitter blades. Numerical examples of the circular cascade composed of nine main blades and nine splitter blades having the same damping coefficients are presented. The flutter velocity is calculated from the flutter determinant which has maximum reduced frequency. The main results are as follows. When the interblade phase parameter of vibration is small, the chord length of the splitter blades is decreased, which reduces the flutter region. Flutter occurs at the vibrating frequency of the blade close to the harmonics of the rotating speed of blade rows. The flutter velocity decreases as the vibration changes from the torsional mode to the bending mode, and increases at a certain chord length of the splitter blades.

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We have constructed a small hot-wire anemometer rotating with a centrifugal impeller, and have measured the mean velocity and the Reynolds stress tensor of the relative flow at the impeller midpassage. The anemometer shows satisfactory performance for wind velocity fluctuation and for linearity between its output and velocity. The mean relative velocity in the impeller passage coincides with that measured previously using a five-hole pressure probe, except that, in the present measurement, the secondary flow is clearer in the region near the shroud surface of the passage. The Reynolds normal stresses are high in the region from the middle blade-to-blade position of the shroud side to the suction surface where loss exists, and the Reynolds shear stresses qualitatively follow the eddy viscosity concept. Therefore, the presented measurement with the hot-wire anemometer seems to be valid for a rotating flow field inside the centrifugal impeller.

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An analytical method was proposed to calculate the unsteady flow induced by the interaction between impeller blades and diffuser vanes/volute casing in a diffuser pump. The singularity method was used for the analysis, and the unsteady flow in the diffuser as well as the volute casing is assumed to be induced by four kinds of unsteady singularities distributed on the impeller blades, diffuser vanes, volute casing wall and free vortices shed from diffuser vanes. The calculated unsteady pressures in the diffuser and volute casing agree well with the measured ones. Calculated results show that the volute casing has little effect on unsteady flow in the test diffuser.

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To predict erosion wear on a pump casing wall due to the impingement of solid particles, a Lagrangian approach is employed to calculate the impinging velocities on the casing wall under the assumption that the water flow field remains unchanged due to the existence of the particles, and the effects of mutual collision among the particles are investigated. With the use of these impinging velocities and Bitter's erosion model, the erosion wear rate on the casing is evaluated and confirmed by Roco's experimental data, showing the applicability of this method for the case of larger particles.

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A generation mechanism is developed describing the shock accompanied with transient structural vibration and audible noise during the reversing cycle at the top-dead center of a hydraulic machine press, and a mathematical model is presented to predict the shock with good accuracy for practical use. Experiments were carried out on a small-sized model hydraulic system dynamically similar to a real machine in the 20-MN class. It is found that the shock is due to the surge pressure caused by the rejoining of a column separation produced at the main ram cylinder end of the prefill line and its intensity is nearly proportional to the magnitude of the surge pressure. The calculated values from the proposed mathematical model agree with the measured values of the surge pressure, cavitation duration following a column separation and movement of the main ram during the reversing cycle with errors within some 10% over a wide operation range.

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From the standpoint of power conservation, bondgraphs represent systems, even those composed of mechanical, hydraulic and electric components, by a unified approach. In this paper, a three-port pressure regulator valve is represented by the bondgraph, in which hydraulic resisters are controlled by orifices having overlap and underlap. The bondgraph of the resisters is constructed with two R-elements consisting of a linear resister and a squared resister. Additionally the effect of mixed air in the oil is easy to analyse by using the initial bondgraph and two additional C-elements. Dynamic behaviour of this regulator valve is obtained easily by bondgraph simulation in comparison with the usual simulation methods.

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A theoretical study has been made of the effect of a circumferential rib on the condensation heat transfer performance of a horizontal two-dimensional fin tube. Numerical calculation was performed for systematically changed values of rib parameters with HCFC-123 as the working fluid. Numerical results are compared with six classes of fin profiles that were proposed in previous studies. The results showed that circumferential ribbing is effective in enhancing film condensation. The effect was more significant for a double rib fin than for a single one. For a typical combination of geometrical parameters of the fin, the average heat transfer coefficients about 58 and 27% higher than the best performing fin profile proposed in the previous studies were obtained using the double rib fin and the single rib fin, respectively.

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Both economy and safety of the nuclear power stations are strongly demanded. One of the problems in the thermal design of a nuclear reactor, especially in BWR, arises near the spacer supporting the nuclear fuel rods. The purpose of the present paper is to make clear the mechanism causing the water film breakdown which results in the burnout of heating tube near the spacer, and its relation to the flow pattern. The experimental results show that film breakdown occurs near the leading edge, i. e., just below the spacer, as well as the inside of the down part of the gap between the outer surface of the heating tube and the simulated spacer.

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The effects of inner rotating horizontal cylinder on the heat transfer in a differentially heated enclosure were investigated experimentally. The aspect ratio of the enclosure height/width was l throughout the experiments. A bakelite cylinder was installed horizontally at the center of the square enclosure, and was rotated at various speeds. Purified water was used for the working fluid. The surface temperature of the rotating cylinder was measured using a telemetry system, and the flow pattern was sketched by a visualization experiment using aluminum powder. It is clarified here that the rotating cylinder suppresses the heat transfer rate of the enclosure in the low rotating speed range because of the interference between natural and forced convections. However, marked heat transfer enhancement can be obtained in the high rotating speed range. The rotating cylinder used here is useful for regulation of wide-ranging heat transfer rate.

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This paper is one in a series of reports on the experimental and numerical study of heat transfer from a module mounted on the floor of a parallel-plate channel to forced convective air flow. In this study a numerical analysis is performed to predict conjugate heat transfer in paths from the module through the module support and the floor to the air flow. The effect of the thermal wake originating from the module on heat transfer from the floor surface is captured by the adiabatic wall temperature function. Also serving as the basis of the analysis is the local heat transfer coefficient obtained and reported in the previous report. The two-dimensional heat conduction analysis with convective boundary condition provides temperature distributions of the floor and macroscopic thermal conductance values for heat transfer through the floor. The predictions are compared with the experimental data, and their good agreement is confirmed.

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We propose a new method of measuring the principal thermal conductivity of a two-dimensional anisotropic heat conductor using a steady heat source and sink. The theory of this new thermal conductivity measurement is based on congruent matrix transformation from nonuniform space of an anisotropic heat conductor to the uniform space of an isotropic one. When we introduce the hypothesis of symmetry in the heat conduction law, it leads to an equivalent relation of the thermal conductivity tensor between the anisotropic tensor Λ_μ and the uniform space tensor Λ_ν. This new measuring method can provide the two principal thermal conductivities λ_{1, 2} and the principal rotation angle φ from the temperature detecting axis. We have measured the temperature dependence of two principal thermal conductivities λ_{1, 2} and the principal rotation angle φ of Y₁Ba₂Cu₃O_7-y. Anomalies of the two principal thermal conductivities and the principal rotation angle are clearly observed at the superconductive transition temperature T_c.

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This paper presents a new methodology for optimal control of an unsteady heat conduction field with heat sources. The optimal control problem considered is that of determining the time changes of heat-source intensities to produce desired temperatures at several reference points. Using Green's functions, which are pre-calculated numerically under a point heat source approximation, it is shown that the distributed parameter system described by a multi dimensional heat conduction equation can be reduced to a lumped parameter system maintaining the distributed property. Thus the optimal control problem becomes low-dimensional and a fast optimal control scheme can be developed for an arbitrarily shaped region. Some examples demonstrate the capability of the proposed method.

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A new type of perforated-plate heat exchanger with crosscut fins is proposed. The proposed heat exchanger is made up of perforated plates separated by spacers. The perforated plates have crosscut fins that are oriented 90° to the axis of flow, and the angle between the fins in consecutive perforated plates can be varied. Experiments were performed to investigate the heat transfer and the plessure loss in the proposed heat exchanger. The following results were obtained. (1) Calculated overall heat transfer coefficients are almost the same as measured heat transfer coefficients for Reynolds numbers above 60. (2) The coefficient of pressure loss is constant for Reynolds numbers above 60. (3) The spacer thickness and the orientation angle of alternate perforated plates don't influence the coefficient of pressure loss.

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Existing correlations are reviewed for heat transfer of high-finned tubes in staggered arrangement, and compared with published experimental data. These data include those using tubes for air-coolers (AC) and for heat recovery heat exchangers in the high-temperature region (HRHX). Comparisons showed that none of the correlations can predict experimental data for both AC and for HRHX. Therefore, a new correlation is Proposed which can Predict almost all data within 10%.

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Numerical simulation of cryopreservation of biological tissues from the view point of heat and mass transfer is carried out to provide a tool for finding optimum combinations of the parameters, such as cryoprotectant mixture concentration and cooling rate. The system considered for the simulation is divided into a number of control volumes, each volume containing several cells. Extra-and intra-cell regions are treated separately. The numerical program calculates distribution of cell size, intracellular concentration of electrolytes and solidification rate of extracellular material during the freezing process. More reliable values of physico-chemical properties such as membrane penetration parameters, and a more precise description of extracellular nucleation phenomena are needed for further development.

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An experimental study was performed on an axisymmetric confined jet with a disk, which was installed coaxially to the jet nozzle. Detailed measurements were carried out with a laser Doppler velocimeter, including the various kinds of statistical turbulent quantities such as turbulent intensities, Reynolds shear stresses, skewness and flatness factors as well as the mean velocities in the axial, radial and circumferential directions. The turbulent structure of the near wake flow is discussed for the cases of U_j/U_s = 1.0 and 3.0, where U_j/U_s is the ratio of the jet and co-flowing velocities. In addition, the production terms in the transport equation of turbulent kinetic energy are examined based on the experimental results.

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A small disturbance analysis is applied to an instability of a liquid-gas interface in a countercurrent annular two-phase flow, considering the curvature of the interface and viscosity and velocity distributions in liquid and gas phases. The analysis indicates that the average velocity, velocity distribution, and viscosity of liquid film significantly affect the instability criterion. Comparison of the present analysis with existing analyses of Hewitt and Imura, in which the viscous effect was neglected, indicates that the viscosity produces two critical boundaries classifying stable and unstable regions instead of the one boundary predicted in the existing analysis.

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Cross-flow between subchannels in a BWR fuel assembly has usually been estimated by three types of mixing models, namely, pressure difference, turbulent mixing and void drift, which are expressed by time-averaged flow parameters. It is important to notice that two-phase flow has an inherent time-varying nature even in the steady-state flow condition. In this paper, we attempted to express the above cross-flow phenomenon by a simple mixing model to which time-varying pressure difference was applied. To examine the validity of the model, a test using an air-water loop with a short mixing zone was conducted and compared with the prediction. Results showed that the model well estimated the experimental cross-flow data without conventional turbulent mixing and void drift model.

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It is necessary to predict the vertical profile of the solid concentration in designing essential features of fast fluidization reactors. The concentration of particles in the practical fast fluidization reactors decreases non-linearly from the bottom to the top. This paper proposes a diffusion equation for the vertical solid concentration profile, taking the following two points into consideration ; the infinitely long chain has a large terminal velocity and each particle can take any velocity in a certain range. The diffusivity is then estimated from the movement of the growing chain based on the concept of "fractal", which is found to agree well with the experiments.

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Simulation model for natural convection was applied to determine the temperature distribution in a base plate with rectangular vertical fins. An estimated velocity V_m derived from the buoyancy and pressure drop eqs. in the duct was used for laminar forced convection cooling in parallel plates and circular tubes with uniform wall temperatures. An experimental study was also performed to check these simulation results and they are found to agree well with each other. Then, this simulation method was extended to analyze natural convection cooling of vertical base plates with inclined parallel fins. The convective heat transfer rate for inclined fins was found to be 14% higher than that for vertical fins.

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This paper presents an experimental validation of the mathematical model of an evaporator and absorber, which are components of a water/lithium-bromide absorption chiller heater. The experimental cycle employs a gas-fired, 176 kW (50 RT) machine, which is mainly used in individually distributed air conditioning systems. One of the features of this model, described in the 1st report, is prediction of both static and dynamic characteristics of the machine, especially transient response to rapid change in external conditions. In this experiment, an immediate change in chilled water flow rate is the input signal. Output signals for comparison with predicted data are transient responses of chilled water outlet temperature, evaporating pressure and cooling capacity derived from chilled water temperature and its flow rate. From comparison between experimental data and values predicted using the model, steady-state analytical error is less than ±3%, and dynamic behavior can be predicted within ±10% analytical error of response time.

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The hot water cycle is preferred as the most effective technology for power generation from heat sources of low temperatures. However, we must determine the attainable efficiency of total flow machines to take full advantage of the technology. Rotating performance tests have been conducted to study the characteristics of a total flow turbine, and the internal efficiency of total flow and flash steam turbines are also discussed. This paper summarizes the experimental and theoretical analysis for hot water power generation system.

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Detailed studies are conducted on film effectiveness of discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a similar configuration to that of typical turbine blades except for the spanwise inclination angle. Secondary air is heated so that the temperature difference between the primary and secondary air is about 20 K. In this case, the air density ratio of the primary and secondary flows becomes less than unity ; therefore the density ratio encountered in an actual aero-engine cannot be simulated in the present study. A spoped-wheel-type wake generator is used in this study. Moreover, three types of turbulence grids are used to elevate the free-stream turbulence intensity. We adopt three blowing ratios of the secondary flow to the primary flow. For each of the blowing ratios, wake-affected adiabatic wall temperature around the test surface is measured with the thermocouples in the test model. The effect of elevated free-stream turbulence on the wake-affected film effectiveness is also investigated. Flow visualization by use of liquid crystal is performed to obtain qualitative information on the film-effectiveness distributions.

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A pressurized coal partial combustor (P-CPC) with two-stage coal supply was tested to elucidate the characteristics of a 7T-coal/d air-blown coal gasifier. As the secondary coal-feed ratio (2ry coal/total coal) was increased, the following phenomena were observed, indicating depression of the coal gasification reaction ; (1) decrease of CO and H₂ concentrations, (2) decrease of calorific value of product gas, (3) increase of hydrocarbon (CH₄ + C₂H₆) content, (4) decrease of carbon conversion efficiency. Secondary coal supply is effective for stable slag discharge and the prevention of the slagging problem in a reductor due to the rapid temperature drop of molten slag. In conclusion, as long as stable slag discharge is obtained, it is effective to lower the 2ry coal-feed ratio to promote the coal gasification reaction, resulting in, for example, higher calorific value of the product gas.

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