The discrete vortex method has been used for incompressible high Reynolds number flows as a simple numerical simulation method. Ohgami and Akamatsu proposed the viscous diffusion model, and applied the vortex method to simulate viscous flow. In this study, we estimate the accuracy of this model both mathematically and numerically, and then show the computational procedures of this method for the case of application to an arbitrarily shaped body. In the discrete vortex method, the surface pressure distribution is calculated conventionally from the unsteady Bernoulli equation, but it is not available for viscous flow. We propose a simple method based on the boundary element method to calculate the pressure distribution for the discrete vortex method with the viscous diffusion model.

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The frequency of vortex shedding from a circular cylinder in oscillatory flows in a pipe is measured. The flow oscillations are induced by means of a rotatable butterfly valve set downstream of the test section. It has been observed that the frequency of vortex shedding varies with both the oscillation-amplitude parameter ΔU/Fd and the Reynolds number Re under constant oscillation frequency. In the case of a large amplitude parameter the frequency of vortex shedding synchronizes with the oscillation frequency of the flow and with one-half of it. The Strouhal number St is nearly constant for a small ratio of oscillation amplitude to the mean velocity ΔU/U, irrespective of the Reynolds number. For large ΔU/U, St decreases with increasing ΔU/U and /or decreasing Re.

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Three-dimensional flow visualization of a vortex-generating region behind a conical axisymmetric body was conducted in a hydraulic flume using computer image-processing techniques. In order to obtain three-dimensional images, a light sheet set normal to the free-stream direction is swept mechanically in the longitudinal direction with periodic motion, and a series of cross-sectional images at very short time intervals of 1/30 second for each sweep were digitized by a video digitizer and input into the computer data storage. Then the time coordinate of each cross-sectional image is converted to a spatial coordinate obtained from the phase information of the sweep to create quasi-instantaneous three-dimensional image data. From the time variation of the three-dimensional images, transitional characteristics of flow behind the body were clarified. In particular, the switching mechanism of issuing direction of spoon-type vortex at Reynolds number of 300 was clarified.

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In order to clarify the mechanism of the severe erosion mainly resulting from the singular vortex cavitation, we carefully observe the vortex cavitation associated with the erosion around a butterfly valve by means of a high-speed video camera, whose framing rate is 40500 per second. The velocity of cavitating flow is measured by the digital-image processing technique. It is worth noting that the vortex cavitation develops in the boundary region between the main flow region, i. e., the orifice-jet, and the recirculating region. The cavitating vortex core consists of several tiny vortex cavitations. The rotating velocity of the highly erosive vortex cavitation can also be determined by this technique.

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The underexpanded jet which is exhausted from the circular nozzle is studied numerically in this investigation. The jet impinges on a flat plate located normal to the jet axis. The axisymmetric Euler equations are solved using a multigrid TVD-type scheme. Jets with different pressure ratios and nozzle-plate distances are simulated. Comparing the numerical results with the experimental ones, good agreement is found and, furthermore, the effect of the nozzle-plate spacing on the wave pattern in the jet can be described. The formation of the separation bubble at a particular nozzle-plate distance is also discussed.

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The expectation that riblets modify the turbulent structure in the near-wall region and reduce skin-friction is experimentally examined in a wall jet. A significant difference is recognized in the mean velocity profiles and the turbulence intensities near the riblet and flat surfaces. The turbulence intensity in the streamwise direction above the riblet surface decreases by approximately 20% in comparison with that above the flat surface. The local skin-friction coefficient estimated from the mean velocity profiles in the viscous sublayer and the buffer layer indicates that the maximum reduction ratio of the drag is 11% at s⁺=30∼35 within the present experimental condition ; this value of s⁺ is considerably larger than that in the turbulent boundary layer.

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Current progress in the field of supercomputers has made possible the direct numerical simulation of the gas-solid two-phase jet based on the Navier-Stokes equation and the Lagrangian equation of the particle motion without the use of any assumptions or models. In this study, three-dimensional Eulerian air velocities and Lagrangian particle trajectories are simultaneously calculated to describe the interaction between particles and air using a two-way method. Although the mesh size is roughly seven times the Kolmogorov microscale, the calculated turbulent characteristics of air and particles (mean velocity distributions and turbulent intensity distributions) are in fairly good agreement with experimental data obtained using laser Doppler anemometry. This means that the simulation well describes the motion of large-scale eddies which play an important role in the formation of turbulent gas-solid two-phase flow.

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Control of a non-equilibrium plasma jet by applying the magnetic field is investigated experimentally. This paper describes the characteristics of plasma parameters, excited temperature and thermofluid characteristics under different magnetic flux densities and under the magnetic field distributions of the mirror and the cusp types. With the increase of the magnetic flux density of the mirror-type, electron density, electron temperature and ion velocity increase rapidly, and furthermore, excited temperature, gas temperature and gas velocity increase slightly only in the core region. These may result from the confinement of electrons by magnetic lines of force, Lorentz force and induced electric field effect. However, the cusp-type magnetic field shows a slight effect on the plasma characteristics, compared to the case of the mirror-type. This implies the mirror-type magnetic field is far better than the cusp-type for controlling the characteristics of a plasma jet.

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A diffusion flame at a low flow rate of propane gas in still air was surrounded by a circular mesh electrode. A circular burner of 8 mm diameter was used as the other electrode. Alternating electric field of high frequency and high voltage was applied between these electrodes. The luminosity which radiated from high temperature soot particles was measured by a photomultiplier. The oscillating frequency of the luminosity changed proportionally up to 80 Hz with the frequency of the applied electric field. The electrical mobility and effective equivalence diameter of soot particles in the flame were estimated by means of the displacement of the luminous signal and the relaxation time of the soot particles. Average values were calculated to be about 0.15 m²/(V·s) and 40 μm respectively. The deformation of diffusion flames at low flow rate has been investigated numerically by the use of a rectangular nozzle in magnetic field. The deformation of the flame was independent of the direction of the magnetic field. The strength of the external force by the magnetic field was proportional to the value of two powers of magnetic field (=H²) . The force exerted upon the boundary between the flame and the air by the magnetic field was one induced by the difference of the volumetric susceptibility between the two gases. The deformation, tilt and turn of the flame are caused by the buoyancy and the induced force by the magnetic field. The numerical analysis of the turn of the flame was conducted using the value of the pressure difference at the boundary between the two gases.

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In the surface finishing line of cold rolled steel, it is desirable to operate a strip run without contacting support of the roll in order to prevent the surface defects. This paper relates the adaptation of fluid cushion force for the electroplating line which we call LCC-H (Liquid Cushion Cell-Horizontal). As a basic study for supporting a thin plate without contact by fluid cushion force, with control of a flow velocity, the numerical analysis and experimental studies are carried out in order to obtain the pressure distributions necessary for supporting the plate and the velocity of fluid necessary to remove gases generated during plating. As a result, non-contacting support of thin plate is achieved by means of the cushion force produced by a jet from nozzles and control of the flow velocity is possible by determing the optimum condition of inlet angle of nozzles.

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Conditional sampling measurements based on the 4-quadrant classification method were made to reveal the turbulence structure of a round water jet and a round gas-liquid two-phase jet moving in the vertical direction using a two-dimensional LDV. In the central part of the jets, the rms values of the vertical and radial turbulence components and the Reynolds shear stress of the two-phase jet are much greater than those of the water jet. This difference is attributable to the wake of bubbles rising upward. The difference becomes very small at the outer edge of the jets. Turbulent motions were classified into four distinct categories : ejection, sweep, outward interaction, and inward inter-action. The contribution of each motion to the Reynolds shear stress and turbulence kinetic energy were determined. Turbulence production was much greater in the two-phase jet than in the water jet. Ejection and sweep were found to be mainly responsible for turbulence production in both kinds of jets.

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It is well known that turbulence models based on the eddy viscosity assumption have been quite successful in the numerical predictions of various kinds of turbulent flows. In particular, the k-εmodel is the most popular and has been proven to be effective in predicting wall shear layer turbulence. The k-ε models, however, show poor performance in the prediction of free shear flows. Such inconsistency is not caused by the crudeness of the eddy viscosity approximation, but by the inappropriate estimation of the relevant time scale of turbulence. Thus, in order to settle this problem, we propose a low-Reynolds-number-type "multiple-scale" turbulence model on the basis of the original model of Hanjalic et al. (Turbulent Shear Flows 2, 1980, Springer), in which multiple scales characterizing a turbulent flow are introduced by dividing the turbulence energy spectrum into two wave-number regions. In the present study, much emphasis is put on making a proposed model applicable to the prediction of near-wall turbulent flows without the controversial wall functions and reproduce the wall-limiting behavior of turbulence quantities. The proposed model has been tested in canonical wall and free shear flows and are found to work quite well regardless of the flow regimes.

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Measurements were made of the time-averaged and fluctuating fluid forces, vortex-shedding frequency and wake structures of rectangular cylinders forced to oscillate transversely at a maximum amplitude of 10% of the length of the front face. The ratio of depth (streamwise dimension) to height (cross-stream dimension) of the cross section ranged from 0.3 to 1.0. The nondimensional frequency F_vH/U₀ (F_ν : frequency of forced oscillating cylinder, H : height of cylinder, U₀ : free-stream velocity) was varied from about 0.08 to 0.20, in which the lock-in region was included. It has been found that a critical depth where the fluid forces attain a peak in the oscillating cylinder is smaller than that of the stationary cylinder. Also, within the lock-in region in which the vortex shedding is perfectly synchronized with the force frequency F_ν of the cylinder only, the fluid forces are found to attain a maximum. Furthermore, it is recognized that the work done by the fluctuating lift changes to positive work, which induces the generation of negative aerodynamic damping from negative work when the ratio of depth to height is smaller than 0.5.

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Low-density choked flow through a parallel plate channel with a narrow gap is studied experimentally for a wide range of Reynolds Numbers. In the region from continuum flow to slip flow, the choked flow is analysed by one-dimensional flow approximation, based on the integrated boundary layer equations, taking into account the slip at the channel walls. The calculated discharge coefficients and pressure distributions agree well with the experimental results for a wide range of Reynolds Numbers, including the slip flow region. A nondimensional correlation equation of the discharge coefficient is proposed as a function of Reh_s/l for Reh_s/l <2×10². In the region from slip flow to molecular flow, the experimental results agree well with those of previous work. A nondimensional correlation equation of C_dl/h_s is proposed as a function of Re for 7<Re<5×10¹.

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Recently, we presented a finite element scheme based on the Petrov-Galerkin weak formulation using exponential test functions, for solving the unsteady two-dimensional natural convection up to high Rayleigh numbers. The incompressible Navier-Stokes equations and energy equation are discretized by a semi-explicit scheme in which velocity and temperature are treated explicitly and pressure is treated implicitly with respect to the time variable. As the time-marching scheme, the fractional step method is also adopted in the work. The resulting numerical solutions demonstrate that the method is capable of solving the set of equations accurately and in a stable manner up to high Rayleigh numbers. The purpose of this paper is to extend the Petrov-Galerkin finite element method using exponential test functions, to three-dimensional natural convection problems. The validity of the present method is shown for unsteady flows in a cubic enclosure through comparison with other existing numerical solutions.

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Recently, flow fields with arbitrarily moving boundaries have been computed by using the moving grid technique. In this study, several numerical methods are compared. It is shown that the key factor, which determines the accuracy of the moving grid technique, is discretization error accompanying grid motion, and the error depends on the algorithm of simulation. In the computational results, the SIMPLER method based on a fully implicit equation shows good agreement with theoretical values, and it is confirmed that the SIMPLER method is effective in simulating moving boundary problems. On the contrary, in the case of the MAC method, discretization errors are caused by grid motion, and the errors tend to increase with the increasing time interval Δt.

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A one-dimensional glottal flow model is presented to shed light upon the mechanism of speech production, from a mechanical point of view. The vocal cords are modeled by a pair of membranes supported by nonlinear springs. The equation of the vocal cord is coupled with those of incompressible separated flow through the glottis and compressible flow in the vocal tract. Numerical results show that the glottal source-vocal tract interaction induces high-frequency components in flow rate and pressure because of acoustic resonance. The synthesized sound of the vowels depending on the vocal tract shape agrees qualitatively in waveform with that of measured human voice. The effect of pulmonary pressure and stiffness of the vocal cord on the fundamental frequency of the vocal cord vibration is examined.

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When the relative flow motion of an incompressible viscous fluid is very small compared with the basic system rotation, the flow field forms an almost rigidly rotating flow. In the present paper, we have constructed a computational method for the almost rigidly rotating flow between the coaxially rotating rotor and housing. The basic equations are axisymmetric continuity and Navier-Stokes equations, which are written with respect to the velocity and the pressure in a cylindrical coordinate system that rotates around the axial coordinate with a constant angular velocity. Coordinate transformation from the physical plane to the computational plane is incorporated to enable simulation of the flow between an arbitrarily shaped rotor and housing. The present computational method is based on the SIMPLE algorithm for colocated grids, and incorporates some devices to stably solve flow fields in strongly rotating systems. Two examples of computational analysis are presented. In the first example of source-sink flow between two rotating disks, the applicability of the present method to the strongly rotating system has been confirmed by a close agreement of the computational velocity profile with the analytical solution of a linear theory. In the second example of the almost rigidly rotating flow between the rotating disk and cylindrical tank, we have numerically considered the flow structure consisting of the Ekman layer, interior region, Stewartson layer and rigidly rotating region.

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Fluid behavior in a two-dimensional vane-type surface tension tank is investigated under a reduced gravity condition by using drop tower and drop shaft facilities. The surface tension tank has a liquid-gas separation mechanism with capillary force, which is realized by varying the gap between the outer edge of the vane and inner wall of the tank. The influence of Bond number, contact angle, and vane configuration on fluid behavior is experimentally and analytically clarified. It is also shown that experimental results agree well with analytical ones especially when the gap is small.

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The dynamic behavior of a magnetic fluid in a laterally oscillated rectangular container was studied experimentally. Frequency responses of magnetic fluid-container system were measured under vertical nonuniform magnetic fields. Relations between the resonant frequency and the applied magnetic field were discussed, and experimental results were characterized by Froude number with consideration of the magnetic effect. Since the apparent viscosity of the magnetic fluid increases with magnetic field, its effect on sloshing phenomenon was examined in detail. Internal pressure on the wall and displacement of surface waves were measured simultaneously.

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Measurements of tangential, radial, and vertical velocity components and pressure distribution in a cyclone dust collector which provides an internal perforated cylinder have been made. It is found that the tangential velocity in the cylindrical section is relatively large and almost the same as in a conventional cyclone without an internal perforated cylinder ; and the inward radial velocity is relatively small and constant at all vertical or circumferential positions between the outer and inner cylinders. It is also found that the static pressure distribution in the radial direction has a shape like a dish, and the pressure drop in the cyclone is considerably small. As a result, the dust collection efficiency was improved to 5%, and the pressure drop was decreased to about 30% compared with the conventional cyclone.

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An experimental study is carried out for a swirling flow pneumatic conveying system in a vertical pipeline in terms of the overall pressure drop and solid flow patterns. The test section consists of a pipeline 12 m in height with an inside diameter of 80mm. Measurements were made for three initial swirl numbers from 0.58 to 1.12, the average gas velocities from 9 to 23 m/s and the solid-gas ratios from 1.5 to 23. Polystyrene, polyethylene and polyvinyl pellets with mean diameters of 1.7, 3.1 and 4.3 mm, respectively, were transported as test particles. It is found that in lower gas velocity range, the overall pressure drop for swirling flow pneumatic conveying was close to that for axial flow pneumatic conveying and that wall static pressure of the former was lower than that of the latter.

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The Lennard-Jones (6-12)-potential-type isotropic scattering model for the direct-simulation Monte Carlo (DSMC) method is presented. This model is an extention of the variable hard sphere (VHS) model in which diameter (collision cross section) varies with relative collision velocity (energy) and deflection angle is isotropic. The validity of the Lennard-Jones (LJ)-potential-type isotropic scattering model is studied by the simulation of argon (Ar) normal shock wave structure. Calculation results, such as number density, velocity, temperature, and heat flux are in good agreement with those of LJ potential.

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A comparison of mistuning effects on the torsional flutter suppression between fully stalled and unstalled cascades is made focusing on fluctuation of the natural frequency and blade arrangment. Numerical results are obtained concerning fundamental characteristics of flutter suppression effects. In both stalled and unstalled cascades, the larger the fluctuation in natural frequency the more stable the cascade. Furthermore, the difference of flutter mode variations caused by mistuning between both cascades is clarified.

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The sailwing has many special characteristics due to its flexible structure. In particular, initially stretched small tension, it shows hysterisis of aerodynamic characteristics against incident angles. It is very interesting to investigate sailwing performance under unsteady conditions, which depends on aerodynamic forces, its profile forms, and damping properties of a membrane, but there have been few papers on the effect of the damping force on the unsteady sailwing. In this paper numerical methods are presented for obtaining an unsteady sailwing. The time variation of profiles and lift forces under an unsteady flow can be calculated, taking account of proportional damping by the membrane. The damping force coefficients used in numerical simulations are estimated by vibrating tests for a cloth of vinyl chrolide and the effects of the damping force on the unsteady characteristics are numerically examined.

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Scroll compressors having orbital mechanisms composed of a ball coupling and an eccentric bushing are successfully used for automotive air conditioners. The mechanism is essential for high performance and high reliability of the compressor, but its ability to restrain rotational displacement of an orbiting scroll is not perfect because of some clearance that exists at the ball coupling. This paper focused on the kinematics of the orbiting scroll supported by the ball coupling and the eccentric bushing. Forces acting on members of the compressor were analyzed theoretically and the causes of the rotational displacement of the orbiting scroll were examined. The analysis revealed that periodic self-rotation of the orbiting scroll occurs within the tolerance limit of the ball coupling during one revolution of the compressor. The tendency was confirmed experimentally by monitoring rotational motion of the orbiting scroll with a high-speed video camera.

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Rotating stalls in vaneless diffusers are studied from the viewpoint that they are basically two-dimensional inviscid flow instability under the boundary conditions of vanishing velocity disturbance at the diffuser inlet and of vanishing pressure disturbance at the diffuser outlet. The linear analysis in the present report shows that the critical flow angle and the propagation velocity are functions of only the diffuser radius ratio. It is shown that the present analysis can reproduce most of the general characteristics observed in experiments : critical flow angle, propagation velocity, velocity and pressure disturbance field. It is shown that the venishing velocity disturbance at the diffuser inlet is caused by the nature of impellers as a "resistance" and an "inertial resistance", with is generally strong enough to suppress the velocity disturbance at the diffuser inlet. This explains the general experimental observations that veneless diffuser rotating stalls are not largely affected by the impeller.

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The collapse and redevelopment of rotating stall cells around the volute tongue were experimentally observed in low flow rate regions in the vaneless radial diffuser. The suitably located angle of the tongue-guide vane was revealed by flow visualization and testing of a blower with the volute casing. Based on the observation of the flow patterns around the tongue-guide vane and measurements of velocities and pressures in the diffuser and in the exit of the blower, a method of improvement of the efficiency in a wide flow range was proposed in the design of radial blowers or pumps.

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Noise emitted from an axial fan is classiffied into two types of noise, that is, rotational and turbulent noise. The former is due to the radiator fan, which is one of the major components of noise generated in an engine compartment, and consists of many efforts have been made to reduce it. In this paper the mechanism of the rotational noise of an axial fan having blades of unequal pitch angles is studied experimentally. By adjusting the attack angle of each blade with the blade pitch and accelerating the flow in narrower passages, the rotational noise was found to be decreased.

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Noise generated by an axial fan is mainly composed of two types of noise. Since the first has discrete frequency components, some of which are very harsh, many methods have been developed to reduce them. Based on the pressure measurement in axial fans having equal and unequal blade pitches, the generation mechanism of the secondary components of the rotational noise has been analyzed. By modeling the pressure fluctuation components as a function of the unequal blade pitches, the rotational noise characteristics have been found to be estimated well for a fan having unequal blade pitches.

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The absorption cross section of the B¹Π_u-X¹Σ⁺_g·(610-720 nm) and C¹Π_u-X¹Σ⁺_g(400-470 nm) band system of K₂ has been determined experimentally in K-Ar mixtures. Absorption spectra of the band system were measured at a gas temperature of 773 K and gas pressures from 10 to 1000 kPa. The number density of K was measured using the total absorption of the 5p-4s resonance lines and number density of K₂ was determined from the equilibrium relation. It has been found that the absorption coefficient of the band system is smoothened by collision broadening of the lines in the band system and becomes constant at pressures greater than 200 kPa. The effects of the gas temperature and the slit function on the absorption cross section are evaluated theoretically.

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We developed in the previous report a simple and low-cost method of measuring thermophysical properties of ceramic materials by stepwise heating. One of the important points in the method was the method of measuring the surface temperature of a specimen in a simple and low-cost manner : the surface-temperature was measured by pressing separated thermocouple wires against the specimen surface to which an aluminum foil was attached to create high electric and thermal conductivities. However, the optimum conditions of the thicknesses of the aluminum foil and the thermocouple wire were not evident in the previous report. In this report the effects of these parameters on the accuracy of the measurement have been investigated theoretically and experimentally by using Pyrex 7740 glass as a specimen, and the optimum conditions of the measurement have been clarified.

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When a water-ethanol binary mixture condenses, one observes dropwise condensation on the liquid film even though either substance is completely soluble in the other. The phenomenon is not well understood. This paper discusses liquid film instability using perturbation theory as the drop growth mechanism. The results show that in drop growth, the Marangoni number (Ma, i.e., the concentration dependence of the surface tension) plays a more important role than the absolute value of the surface tension. When a pure, single-component vapor condenses, dropwise condensation does not occur because Ma of a pure substance is always negative ; however, in a binary mixture, the surface tension may be different, and therefore the possibility exists that Ma is positive. If so, the mode of condensation may become dropwise. However, this will depend on the diffusive resistance which, if lowered, makes dropwise condensation more difficult.

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Droplet evaporation on a hot surface under super-gravitational fields was experimentally inves tigated. A test chamber attached to the end of a rotating arm was constructed to produce the quasi-super-gravitational fields. A hot surface, droplet-forming equipment and a video camera for measuring the lifetime of a droplet were installed in a test chamber. Lifetime curves of water, n-decane and benzene were measured under the gravity of G = 1 to 12. As a result, it was found that an increase of the gravitational acceleration led to the decrease of lifetime near the Leidenfrost point.

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This study aims at grasping the microscopic structure during slow freezing of human red blood cells, in relation to the mechanism of slow-freezing injury of cells. The process of directional solidification of suspensions with human red blood cells was observed for various cooling rates using a light microscope with a directional solidification stage, and a video system. Two kinds of solutions for suspension were used : physiological saline and physiological saline with 20% v/v glycerol, a common cryoprotectant. While the ice crystal growing in physiological saline had a cellular structure after a transition of a flat freezing interface into a cellular interface, the ice crystal in physiological saline with glycerol had a dendritic structure. It was found that the manners of interaction between the ice crystal and the cells are considerably different in two solutions. The possibility of a mechanical action of the ice crystal on the cells was discussed, and a classification of the patterns of interaction was proposed.

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A non iterative method for the identification of heat sources in a solid body is proposed by combining analytical and numerical approaches. In this method, imaginary heat sources located on the temperature observation points are introduced. Then the relationship between the observed temperature and the response temperature of the imaginary heat source is derived from the symmetry of Green's function, which gives a formal solution of the heat conduction problem. Using this relationship, for example, it is shown that the location and the intensity of a single heat source can be identified from only three observed temperatures, by executing four numerical simulations, in the case of a two-dimensional problem. In addition, the relationship is easily expanded to three-dimensional and to multi-heat-source problems. Some computational experiments demonstrate the capability of the proposed method.

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A very small film heater with an area of 0.1×0.25 mm², which is immersed in either water, ethyl alcohol or toluene, is heated with an extremely high rate of temperature rise of 93×10⁶ K/s at the maximum. The aspect of nucleation is photographed and the temperature of boiling incipience is measured versus the rate of temperature rise. Under the condition of high rise rate, a large number of tiny bubbles are formed concurrently on the heater surface, and the temperature of boiling incipience becomes constant and almost equal to the theoretical homogeneous nucleation temperature for ethyl alcohol and toluene, whereas it is about 19 K lower than the theoretical one for water. The number density of the nucleated bubbles is measured and compared with that calculated by the nucleation theory. The maximum number density of bubbles is plotted versus the rate of temperature rise. The phenomenon observed at a high rate of rise is concluded to be due to fluctuation nucleation.

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Rapid transient free-convective heat-transfer characteristics from a horizontal platinum wire in supercritical carbon dioxide were studied experimentally. Time history of correlations between heat flux and superheat was shown for various step heat input, and a comparison of the time histories between supercritical and subcritical CO₂ was made. In the case of transient heat transfer to supercritical CO₂, the occurrence of a bubble-like structure was observed.

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The radiation heat exchange between a fluidized bed and heated surface was investigated via an optical experiment employing a He-Ne laser and by corresponding numerical simulation analysis. A model for predicting the radiation heat transfer is subsequently proposed, which considers the thermal boundary layer near the heated surface. The numerical results indicate that radiation heat transfer is enhanced when the penetration depth of radiation is greater than the thickness of the thermal boundary layer. The numerical results are also in good agreement with radiation heat transfer measurements. This is explained by the fact that the radiation is effectively between the heated surface and low temperature fluidized particles outside the thermal boundary layer.

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The augmentation of direct heat removal from small-scale heating elements by an electrohydrodynamically (EHD)-induced flow was experimentally investigated. The shape of electrodes, polarity, electric field strength and electric conductivity of a working fluid were systematically changed to clarify the heat transfer mechanism. By applying electric field, the increase of the heat transfer coefficient of FC-72 (CFC) for a 25 mm² heating element was enhanced 1.8 times at maximum compared to those with no electric field. For a 0.25 mm² heating element, it remained at 1. 2 times. However, the heat transfer coefficient for the 0.25 mm² heating element is about 15 times greater compared with that for 25 mm² due to the fin effect of the substrate. By using a mixture of R113 and ethanol, the heat transfer coefficient was increased about 10 times at maximum compared to those with no electric field, which was proportional to the power consumption.

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Numerical analyses were performed for mixed-convection heat transfer in a square flow channel with uniform wall temperature. Three-dimensional governing equations were solved for Re = 100, Pγ = 0.72 and Gγ/Re² = 0∼50 by finite volume and pressure correction methods. The local flow and thermal development were examined across the cross section and along the flow direction. The effects of Gγ/Re² were shown for the local behavior of Nusselt number and the position of the peak. The development of buoyancy-driven roll generates a three-dimensional reverse flow and prevents the main flow in the thermal developing region. Numerical analysis was also performed for the square channel with an adiabatic entry channel.

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Two-dimensional jet impingement onto a circular cylinder of 50 mm diameter was studied. Particular attention was paid to a case when the cylinder was located in the converging flow field formed between the two flat plates mounted symmetrically near the cylinder. Nozzle-to-cylinder distance was changed in three steps, mainly 3, 7 and 10 times the nozzle width (15 mm), and the jet velocity was changed in the range of 8∼15 m/s. The effects of the narrower end of the converging flow space between the two plates and of the space between the cylinder and the plates on the flow-field and the heat transfer from cylinder were examined. In the case of relatively small cylinder-to-plate spacings, reattachment of the separated flow onto the cylinder surface was observed and the local Nusselt number was found to take a maximum near the reattachment point. Then, an increase by about 9∼12% of mean Nusselt number was obtained.

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The effect of the split heating plate is tested in the application of the latent-heat-thermal energy storage system in order to enhance performance in the melting process. A heating plate with a number of split fins is devised having both the fin and the split-heating-plate effect as well as being feasible to manufacture. Its performance was verified by a variety of experiments : the melting rate is successfully increased by using this heating plate with split fins compared with the case of nonsplit fins. Observed melting patterns illustrated how the size of the fin should be determined in order to achieve uniform melting along the fin surface. Moreover, by examination of the influence of the inclination angle from the horizontal, it was determined that the inclination of the fins induces no improvement in melting rate.

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A mathematical model for evaporator and absorber, which are components of a double-effect, water/lithium-bromide absorption chiller heater, is developed. The purposes of this model are to discribe the dynamic behavior of the machine, and to investigate optimum control method and internal configuration of the machine. In order to satisfy these demands, the model is constructed, based on the internal configuration of the machine which is currently manufactured. The evaporator and the absorber of the machine take the form of a shell and tube heat exchanger. There is a sprinkler inside the evaporator and the absorber, and thus there is falling film. Therefore, both these two components feature the following elements : vapor, liquid refrigerant or solution, heat-transfer tubes, and circulating water. Each of these parameters is classified according to its flow direction. A lumped approximation is adopted for these elements, and the heat capacity of heat-transfer tubes is taken into account. A time lag of the system given by the circulating water in the tubes can be estimated with this model.

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The thermal properties of the test O/W-type emulsion were described in the first report. This paper dealts with flow and cold heat-storage characteristics of the oil (tetradecane, C₁₄H₃₀, freezing point 278.9 K) /water emulsion as a latent heat-storage material having a low melting point. A coiled double-tube heat exchanger was used for the cold heat-storage experiment. The pressure drop, the heat-transfer coefficient and the finishing time of cold heat storage in the coiled tube were measured as experimental parameters. It was clarified that the flow behavior of the emulsion as a non-Newtonian fluid played an important role in cold heat storage. The useful nondimensional correlation equations for the additional pressure loss coefficient, the heat-transfer coefficient and the finishing time of the cold heat storage were derived in terms of Dean number and heat capacity ratio.

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This study is concerned with the method of improving the performance of insulating porous layers which contain a thermal screen consisting of a row of heat pipes. Two experiments are conducted : one using porous layers consisting of nitrogen gas of high pressure and glass beads, and another using a Hele-Shaw cell with encapsulated liquid crystal migrated into a test liquid. It is experimentally confirmed that the thermal screen introduces strong uniformity in temperature distributions such that temperature profiles approach to those for thermal conduction and that the thermal screen can suppress convection in the insulating porous layers and improve the performance of the insulation.

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We numerically investigated an effect of coherent vortices in a two-dimensional reacting shear layer on flame growth. The vortices may contribute to combustion phenomena, and moreover, flame performance. In this study, we attempted the numerical analysis of the diffusion flame structure in the shear layer, in the early stage from the ignition, by solvig the time-dependent Navier-Stokes equations with the finite difference method, assuming the reaction is one-step and irreversible. The HSMAC method was modified so as to take the fluctuations of density and temperature into consideration. The calculation revealed the important result that heat transfer to the fast fluid caused by coherent vortices in the mixing layer provokes the blowoff.

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Instantaneous spatial temperature profiles are measured by means of a laser Rayleigh scattering method using a detector which has multiplepoint elements in a single line. The instantaneous temperature profiles could be detected without influence from chemiluminescence by use of a pulse YAG laser. This method was applied to the measurements of three typical turbulent diffusion flames with different degrees of turbulence. The results obtained are as follows. (1) The average and instantaneous maximum temperatures tend to decrease when the Raynolds number increases. (2) The probability density functions (pdf) of temperature in the flame have broad profiles. This indicates that burned gas of various equivalence ratios is mixed in the flame. (3) The rms values of temperature fluctuation both inside and outside of the flame are high. Temperature fluctuations on large spatial scales are predominant in the flames. The scales of the temperature fluctuations do not depend significantly on the Raynolds number.

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A temporal change of local electron temperature on the central axis of the plasma jet was measured in an enivironment of hydrogen. The electron temperature was measured by applying the two-line radiance ratio method. The diffusion of plasma jet was clarified for various plasma jet igniter configurations and supplied electrical energies. The relationship between the characteristic length of the igniter and the plasma jet was elucidated. The progression of the plasma jet was influenced by the waveform of the discharged voltage in the vicinity of the igniter. The electron temperature and the length of the plasma jet increased as cavity volume decreased and as orifice diameter increased. It appears that an igniter which has a small characteristic length is favorable with regard to penetration of the plasma jet and to generation of a high electron temperature. Therefore, it is considered that the plasma jet igniter configurations exert different influences on plasma jet penetration and combustion enhancement.

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