A method for solving three-dimensional viscous incompressible flows is presented. A complete set of the Navier-Stokes equation is transferred and expressed in terms of the vorticity, the scalar and the vector potential. In this formulation, the velocity field satsfies the equation of continuity automatically. The vorticity transport equations discretized by the centered differences are solved by the rational Runge-Kutta (RRK) time integration scheme, and the Poisson equations are solved by the successive over-relaxatation (SOR) method. The numerical solutions of flows in a cubic cavity, in a square duct and in a rectangular duct with the aspect ratio of 2 are presented. Comparison of computed results with other calculations confirms the accuracy and reliability of the present approach.

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This paper describes an analytical method for the jet flow through a nozzle into the atmosphere. The flow is assumed to be two-dimensional, incompressible, steady and laminar. The velocity profile at the exit of the convergent channel is assumed to be that of Hamel's flow. A streamline coordinate system is adopted for governing equations. The velocity distribution across the jet flow is expanded to a Fourier series. Simultaneous first-order ordinary differential equations are obtained from the Fourier coefficients. Starting with the exit of the channel, the flow field is solved numerically step by step in the downstream direction. Numerically predicted outcomes are being considered for comparison for Reynolds numbers of 300, 400 and for different jet angles. Good agreement between the analytical and numerical results is found.

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Micropolar theory, and the thermodynamical method are unified to derive a new complete set of equations for magnetic fluids. Some strain tensors are defined using micropolar theory, and the electromagnetically and kinematically balanced equations are obtained considering both the viscoelastic effect and internal rotation. Using the principle of material frame indifference and the principle of maximal dissipation rate, the constitutive equations including nonlinear terms are determined from the thermodynamical relations such as Gibbs equation and the dissipation function. These equations can represent the behavior of magnetic fluids sufficiently when viscoelastic effect, internal rotation and nonlinear effect are considered.

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A numerical simulation of a gas-solid two-phase flow in a vertical upward pipe is performed to examine the influence of collision between particles by using the same probability model which was proposed in the previous paper. We use coarse particles of uniform size as well as heterogeneous size and assume the velocity profile of air as uniform or 1/7th power law. The results show that the collision between particles promotes the particle dispersion both in the axial and radial directions of the pipe.

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The three-dimensional flow field through a linear cascade with tip clearance was numerically studied by solving Navier-Stokes equations. A fundamental cascade model composed of flat plates, for which corresponding experimental data were available, was adopted to develop the appropriate solution method for the flow through the tip clearance. The computed normal force distributions on blades and velocity vectors in the downstream flow field showed good agreement with the experimental data. The detailed flow phenomena around the blade tip, such as the formation of separation bubbles on the tip surface, were clearly described. The spanwise distributions of the normal force on the blade were investigated for various tip clearances, and it was found that the normal force on the extremity of the blade did not diminish in the case of small clearances of less than 0.6% of the blade span because of the blockage of leakage flow due to the effect of viscosity.

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A method is presented for the numerical analysis of the aerodynamic characteristics of sails in a cascade when all sails take the same shape. In this analysis, the authors apply a series of Chebyshev polynomials to express the pressure distribution and chordwise shape. It is found that the aerodynamic stability of a sail decreases with increasing stagger angle from the viewpoint of the values of maximum tension eigenvalues, but it increases when we judge it in terms of the critical excess length ratio. The effects of stagger angle on the values of the lift coefficient and the position of the center of pressure are shown in diagrams as functions of an angle of attack, solidity and excess length of membrane over the chord length.

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Fluid forces and moment acting on a blade of a Darrieus-type runner were measured in addition to the blade performance. The characteristics for various type of blades were evaluated from the measured data with theoretical considerations in an inviscid flow. Some features of those characteristics, including the dynamic effects caused by an unsteady relative flow around the Darrieus blade, are shown in the present paper. For high efficiency, a noncambered thin blade with relatively long chord length is recommended. Its characteristics are high lift slope, high lift at zero angle of attack and relatively low drag in a wide no-stall region of attack angles. It should also be set tangent to the runner pitch-circle at the 50% chord point of the blade.

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This paper aims to clarify the laminarization phenomena of strongly heated gas flows within concentric annular tubes. In the first place, the authors' former experimental results, in which annular flows were strongly heated exclusively from the inner side of the annulus, are examined by means of a k-ε model that was previously modified by the authors so as to reproduce the laminarization of strongly heated circular tube flows. Numerical results indicate a certain amount of turbulent kinetic energy remains in the flow field so that the observed heat transfer reduction is judged not to be due to laminarization, and the attention is turned to the case in which the flow is heated from both sides. A remarkable reduction in heat transfer is observed in both numerical and experimental results, and the corresponding turbulent kinetic energy is found to be uniformly attenuated over the whole tube cross section so that it is concluded that the reduction is certainly due to laminarization. Following the results, some discussions are developed on the occurrence criteria of laminarization of the annular flows, and the obtained criteria are in fairly good agreement with the experimental results by Ogawa et al.

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Counter-current-flow limitation (CCFL) experiments were carried out for both vertical rectangular channels and vertical circular tubes varying in size and in configuration of their cross sections to clarify CCFL characteristics in the vertical rectangular channels. Quantitative understanding of critical heat flux (CHF) in a narrow vertical rectangular channel is required for the thermohydraulic design and safety analysis of research nuclear reactors in which flat-plate-type fuel is employed. Critical heat flux under downward low velocity is closely related to falling water limitation under a counter-current flow. Experimental results showed that the equivalent hydraulic diameter de, i.e., the width, and gap of the channel play an important role in determining the CCFL characteristics of a rectangular channel. However, a significant influence of channel length on CCFL characteristics was not observed in the ranges investigated. Using new dimensionless parameters, the authors propose a correlation for predicting the relationship between upward air velocity and downward water velocity based on the present experimental results.

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The physical properties of a supercritical fluid vary drastically near its critical point. In this paper, heat transfer due to an axisymmetric laminar impinging jet onto a flat wall surface of uniform temperature is analyzed numerically, taking into account the pressure- and temperature-dependence of all physical properties of near-critical carbon dioxide for the jet Reynolds numbers 500-2000, the jet pressure 7.4-8.4MPa, and the temperature difference between the jet mouth and flat wall from 10K to 150K. The effects of the temperature and pressure of the jet, the jet-to-wall temperature difference, and the jet Reynolds number on the heat transfer characteristics are examined.

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The surface has been treated as perfectly smooth in the analysis of absorption of water vapor into falling film of aqueous lithium bromide solution. However, waves or disturbances begin to appear at Re_f of 20. In this paper, the influence of the waves is analyzed numerically by assuming sinusoidal wave motion over the falling film. The velocity profile inside the film is determined following Kapitza's analysis. The wave velocity and the wavelength are determined from Pierson and Whitaker's equations derived from the stability analysis. The wave amplitude is assumed to be 30% of the average film thickness. The liquid surface is immobilized by coordinate transformation and the basic equations are further changed to eliminate the cross derivative terms by Shyy et al.'s method. The results are compared with those for a laminar flow with a smooth surface. It is found that the absorption rates increase by a factor of 1.7-2.4 over the Re_f range of 20-100.

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The present study is a basic investigation of the phase-change problem of a TES material consisting of a phase-change material (PCM) and conductive solids to promote the heat transfer rate. As the first step, experiments were carried out, using water containing coiled copper wires as the TES material. The phase-change process was investigated varying factors such as the volume ratio and the arrangement of the wires within the PCM. As a result, it was found that the phase-change rate of the TES material was increased considerably by the addition of the wires despite the small effects of the volume ratio and the arrangement. The heat transfer model of this TES material was proposed, and the numerical calculation was performed to simulate the phase-change process. The calculated results agreed well with the experimental results.

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The contact area of boiling bubbles on the horizontal heating surface of transparent glass was observed from the back side of the heating surface through a transparent fused salt in transition boiling. The boiling liquid was Freon R-113, and the experiment was performed under the saturation condition at atmospheric pressure. The behavior of bubbles and liquid on the heating surface was observed in transition boiling by means of photography. As a result, the ratio of the area of the microlayer in contact bubbles on the heating surface to the total area of the heating surface decreased and the ratio of the dry contact area of the bubbles on the heating surface increased with increasing of the superheat of the heating surface.

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This paper presents a simple model for natural-convection film boiling heat-transfer in staturated liquids for inclined plates. The model assumes that a vapor film has two-dimensional laminar vapor-film units that line up in the longitudinal direction of the plate. To determine the pitch of these units, the model uses the Kelvin-Helmholtz instability analysis. The model agrees with experimental results on heat-transfer coefficient as for the effects of the parameters : fluid properties, surface superheat, surface height, and surface inclination. Besides being applicable to flat surfaces, the model can be successfully extended to the case of saturated film-boiling around large horizontal cylinders. The paper also examines by an experiment in saturated liquid nitrogen the validity of the assumptions made in the analysis, concerning the interfacial behavior of film boiling on a vertical flat plate.

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An experimental study was performed on the permeability of screen wicks using water. An equation for the wick porosity influencing the permeability was also proposed based on a model of the screen geometry. In the present experiment, the screen mesh size, number of screen layers, packing condition of the screen and flow rate were varied. For the friction factor, a correlation C_f=A/Re was obtained ; here the coefficient A was related to the packing number ω defined by the ratio of n-layer thickness to n-times the single-layer thickness of the screen. Consequently, it was found that the permeability of the screen wicks could be predicted considerably well from the expression presented in this study and increased steeply with the increase in the packing number ω, which showed the degree of hold-down pressure for the screen wicks.

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An application of a holographic interferometry technique was demonstrated for measuring the steady and unsteady state temperature distributions in two liquids, water and n-propanol. The deflection and temperature errors caused by refraction, which is the most important source of errors within a steep temperature gradient field such as the thermal boundary layer, were discussed and estimated. Estimated errors in the measured temperature of the liquid phase under spreading flame conditions for a 0.5cm path length of n-propanol with 250°C/cm temperature gradient are within 2%. The technique required : (1) transparency of the liquid and (2) availability of the relation for the thermooptic coefficient of the liquid with temperature. If these requirements are satisfied, the temperature distribution within the liquid phase can be measured with a spatial resolution of as high as 20μm.

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A new characteristic temperature, the "adiabatic limit flame temperature", has been proposed in this paper; it is an inherent temperature of a combustible mixture based on the thermochemical properties of the constituents. The concept of this temperature is very important, especially in the consideration of a combustion system with energy recirculation between products and reactants. Since this is the highest temperature attainable in a combustion system with no auxiliary energy input, the available energy and the efficiency of the system should be estimated based on this temperature instead of on the adiabatic flame temperature. An illustrative example of a system of reaction between diatomic molecules is shown, and the characteristics of the temperature are discussed. The low calorific limit of flammability is also discussed in this paper.

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The tubular flames of lean methane/air mixtures in a rotating-flow field have been analyzed for their concentrations of stable species and temperature distributions, and their structures have been investigated. The results show that the tubular flame consists of an inner hot gas core of burned gas and an outer region of the unburned mixture, and that the flame structure is essentially the ssme as that of one-dimensional, flat, premixed flame. As the extinction limit is approached, the flame diameter decreases and the concentrations of carbon monoxide and hydrogen behind the flame zone increase. Hence, the extinction of the tubular flame of lean methane/air mixtures is csused by incomplete combustion with stretch as it is with other stretched flames. As the density inside the flame is lower than that outside, the flame front is rendered smooth and cylindrical by the rotational motion of the flow.

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Exciplex-based fluorescence thermometry was developed for remote probing of fuel droplet temperature. The liquid fuels tested were n-Heptane, n-Decane and n-Hexadecane which contained 1% Naphthalene and 2.5% Tetramethyl-p-phenylene diamine (TMPD). Also examined was unleaded regular gasoline into which no Naphthalene or TMPD was dissolved. The fuel droplet suspended at the tip of a quartz fiber was allowed to evaporate in a stream of air or gaseous Nitrogen, and its temperature was monitored using a fine thermocouple. The droplet was irradiated with a Nitrogen laser and fluorescence emission spectra were taken by means of a light collection system which consisted of a convex lens, a light stop, a double monochromator and a photomultiplier. The results showed that remote probing of the droplet temperature could be achieved by measuring the ratio of fluorescence emission intensities at two different wavelengths.

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OH fluorescence induced by a XeCl excimer laser was detected in a laminar diffusion flame. The OH concentration and temperature in the flame were estimated by OH fluorescence and Rayleigh scattering. The results obtained are as follows. (1) The spectrum of OH fluorescence was numerically simulated by rate equations taking account of many absorption transitions excited by the XeCl excimer laser and it predicted the experimental results well. (2) Relative and absolute OH concentration were estimated by the measured fluorescence and rate equations. (3) Rayleigh scattering was separated from OH fluorescence to measure flame temperature. The measured temperature agreed with that obtained by the use of Rayleigh scattering by an argon ion laser.

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The laminar burning velocity and the turbulent burning velocity of propane-air homogeneous mixture in a closed vessel were successfully measured from the difference between the flame propagation speed and the unburned gas velocity ahead of a flame front. The unburned gas velocity was measured with a laser Doppler anemometer. The flame propagation speed was determined by measuring the time of flame travel over a fixed distance. The flame front was detected by the refraction of a laser beam owing to the rapid change in the refractive index at the flame front. It was found that these measured values were reasonable as compared with the values determined from the configuration of flame and the pressure in the combustion chamber.

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In order to improve the accuracy of the numerical prediction of gas flow in intake ports, a porosity approach has been applied to control volumes adjacent to walls. Numerical prediction of intake port flow has been carried out under steady flow conditions. By comparing the results of numerical predictions using the porosity approach with those using the previous approach of representing wall surface with staircaselike boundaries, it was confirmed that the accuracy of flow prediction was improved considerably by using the porosity approach. It has therefore become feasible to predict pressure losses in intake ports quantitatively. Consequently, an improvement in accuracy is expected in the prediction of volumetric efficiency and swirl intensity under the operating conditions of actual engines by applying the porosity approach.

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Behavior measurements have been made of an aluminum-impregnated carbon apex seal of 6mm in thickness and a chilled cast iron apex seal of 3mm in thickness. A new magnetic induction system consisting of transmitting, resonance and receiving printed-board coils was devised. An inductive-type sensor was connected with the resonance coil, being intermediate between the others. Quantitative measurements with high frequency response became possible with this system. It was found that at speeds higher than about 3000rpm and loads higher than 2/4, the cast iron apex seal had a tendency to vibrate after the shift from trailing to the leading side of the slot after the minor axis of the rotor housing on the ignition side.

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