To improve the physical understanding of the fatal "violent vibration" in the near-transition range, the "abrupt cavity separations" associated with the vibration were precisely observed in a water flow around two-dimensional hydrofoils, for various angles of incidence and cavitation numbers, by means of high-speed photography. The cavity separation is a periodic phenomenon that the subcavitating cavity and the supercavitating cavity form alternatively between several spanwise locations, accompanied with a bubble cloud shedding from the subcavitation cavity. The cavity separation line becomes highly distorted immediately after the shedding.

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From the standpoint of engineering and industry or space engineering, it is important to study the interference characteristics of an underexpanded jet. It is the purpose of our studies to clarify the basic interference characteristics of underexpanded jets issuing from several pipes towards the atmosphere. In this paper, the interference characteristics of two parallel underexpanded jets for various intervals between two pipe axes were studied. In particular, the flow visualizations of both mean and instantaneous flows with time, the pressure and velocity distributions, and the equi-velocity diagrams within a vertical section to the jets axes were investigated. Moreover, using two light sources, the flow visualizations by simultaneous exposure of the mean and instantaneous flows with time were attemped. As a result, it was found that the mean and instantaneous flows could be visualized simultaneously, and moreover that these jetflows could be classified into 3 patterns.

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Experimental investigations of the aerodynamics of a circular cylinder in oscillating flow have been made at Reynolds numbers of (1.1∼1.7)×10⁴. The vortex-shedding frequencies, time mean and fluctuating pressure distributions on a cylinder in sinusoidal gusts with various frequencies and amplitudes have been obtained. Fluctuating fluid forces acting on a cylinder have been separated into two parts, i. e., and oscillating fluid force due to vortex shedding and that due to the flow oscillation, using a computer-aided flow visualization technique. The lock-on phenomena occur in the frequency ranges near the natural vortex-shedding frequency and at twice this value. The alternative nature of vortex shedding is maintained in both locked and unlocked conditions, but an appreciable increase in an oscillating lift force appears in locked-on ranges. The oscillating lift and drag forces due to flow oscillation are proportional to the gust velocity components in their individual directions.

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The vortex shedding from a circular cylinder in a laminar boundary layer has been investigated experimentally. The circular cylinder was placed at various distances from a flate plate. Experiments were carried out under the Reynolds number less than 10³. The frequency (f) of the vortex shedding from the circular cylinder is proportional to the velocity (u_c) which is velocity at the center of the circular cylinder in case without the cylinder. This means that, at higher Reynolds number, the Strouhal number is constant as is in the uniform stream. This constant Strouhal number depend on the combination of the cylinder diameter and the gap between the cylinder and the wall, but it does not depend on the Reynolds number and the boundary layer thickness. From these results, the reference velocity which ought to be used for the vortex shedding phenomena from the circular cylinder in the laminar boundary layer is defined.

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The effect of the disturbance of a circular cylinder on the diffusion process of matter from a continuous point source in grid-generated water turbulence has been investigated experimentally. In this paper, the characteristics of the conditional statistics are mainly examined and compared with the results concerning the mean and fluctuating concentration field reported in the previous papers. The data downstream of the cylinder show that the vertical profiles of the conditionally-averaged mean concentration in plume show near constancy in the extensive region containing the plume axis, and those of the conditionally-averaged concentration fluctuation rms value have double peaks .The auto-correlation coefficients of the intermittency function behind the cylinder have apparent periodicity, and this suggests that meandering of the plume is caused by the Karman vortex. On the plume centerline, it is found that the conditional relative intensity decreases downstream by the disturbance effect of the cylinder, whereas that without the cylinder does not change downstream.

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A new integro-differential solver is developed and applied for calculating flows along NACA 0012 airfoil at angles of attack. The present method is formulated by the vorticity and the stream function. The spatially discretized vorticity transport equation is solved by the rational Runge-Kutta (RRK) time integration scheme in the vortical flow region limited to the vicinity of the airfoil, and this method is also applied for solving the pseudo-unsteady Poisson equation with convergence acceleration techniques. By the present method the direct simulation of the flow along NACA 0012 is successfully carried out at the Reynolds number 10⁴ and the angle of attack 5 degree.

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Laminar flow in the bends of a rectangular cross-section is numerically simulated by a direct integration of the full Navier-Stokes equations. Based on the numerical results for a strongly curved 90 degree square bend, detailed descriptions are made of the flow near the entrance and the exit of the curved section .The discrepancy between the experimentally visualized flow pattern and the actual flow field is also demonstrated, suggesting the inclusion of the upstream history in the experiments. The numerical results of a 180 degree bend of an aspect ratio 2 is compared with recent LDV measurements . The agreement is quite reasonable.

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This paper describes an experimental investigation of pressure reduction, which is initiated by a sudden discharge of compressed air from a long pipe installing branch pipes to the atomosphere. The experiments have been made by changing the geometrical parameters : main pipe length, branch pipe length and orifice ratio. It has been made clear that the time Δ_to for the pressure reduction ratio ξ=0.17 in branch pipe length Y=1.5 m is almost the same as that for the case without branch pipes. The time Δ_to is not greatly affected by the branch pipe length in the case of the main pipe length being relatively short, but it is affected by the branch pipe length in the longer main pipe.

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The phenomenon, that the flow rate of a loop with a cross pipe switches nonperiodically between a high level and a low level under certain flow conditions was experimentally investigated by using air flow test equipment (Re≒2×10⁵). The influence of the branching discharge ratio and structural factors (e.g. the offset angle and length of laterals of the cross pipe) on the phenomenon was found. A switching occurs in the case for the offset angle of about 8 to 20°, and it is restricted within a certain range of the branching discharge ratio. The discharge ratio of the center branching pipe to the main pipe at the peak value of the branching loss coefficient increases as the offset angle increases. In the case for the flow rate of the lateral exceeding about 1.7 times as that of the opposing lateral, switching does not occur.

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By assuming a uniformly converging radial flow on the upstream side of an orifice and integrating the equation of motion, an expression was derived to estimate elongational stresses for dilute polymer solutions at the orifice exit from pressure drops between the upstream and downstream of the orifice. The expression shown that the dilute polymer solutions usually give lower values of pressure drop than the solvent (water) does. An experiment was carried out to obtain the pressure drops for the orifice flow of water and dilute polyethylene exide (PEO)-water solutions. It was confirmed that the dilute PEO solutions yield lower pressure drops than water and the elongational stresses were estimated by the above-mentioned relation. The estimated elongational stresses broadly agreed with the ones previously obtained by a jet thrust method.

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The structure in an initial mixing region of a two-dimensional curved jet along a circular arc is investigated by measuring the turbulent energy balance and the Reynolds stress transport. The results show that the profiles of the terms in the turbulent energy equation and the Reynolds stress transport equation exhibit an obvious asymmetry due to the influence of the centrifugal force. Each term is clearly enhanced in the outer shear layer of the curved jet and is reduced in the inner shear layer. However, the generation term and the pressure- strain redistribution term in the Reynolds transport equation exhibit an obvious asymmetry only within the region of about a few slot thicknesses downstream of the nozzle exit, and the asymmetry of these terms decays vary rapidly.

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Measurements of the turbulence property of a bounded jet flow in the case of a nozzle aspect ratio of 2 have been carried out, prescribing the initial turbulence intensity and the nozzle shape. As a result, the turbulence intensities and the turbulence kinetic energies on the jet-center axis show remarkable variations against those of the two-dimensional jet. The distributions of the Reynolds stress correspond well to those of the mean velocity on the jet center plane of the bounded jet, including the existence of the velocity excess. Furthermore, turbulence properties of the bounded jet have been clarified from the variations of the large scale eddies in the turbulence structure on the jet-center axis and the jet center plane by using auto-correlations and the power spectra.

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Unsteady flow through a taper nozzle produced by piston impact is examined by numerical analysis, pressure measurements and jet photographs. in the numerical analysis, Tait's equation of state and the homogeneous model of vapor cavities are employed for one-dimensional flow in a pipe with an area change. The flow velocity is rapidly increased by the incident pressure in the taper section. Vapor cavities are formed during flow-velocity decreases at the nozzle outlet. The cavitation also spreads into the water column from the piston front because the piston separates from the column due to the reflection of the impact pressure. The density and the velocity of flow change discontinuously at the interface between the cavitation and the water. It is illustrated that the nozzle opening ratio effects the jet speed.

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A flow past a perforated plate produces a whistle or vibration. So to elucidate such phenomena, an experimental study was conducted on the production of ring vortices from plates containing a single or some holes. The mechanism and frequency of vortex shedding was determined as a function of the Reyolds of the jet. At Reynolds numbers below 3000, vortex rings are formed in the circular jets with a Strouhal of 0.6. This phenomena is not influenced by the hole length. At Reynolds numbers above 3000, vertex rings with a Strouhal number of 1.6 are formed at the entrance of a hole after their fovmation some vortex rings combine with other in the hole of at the downstream of the hole. Hence in this way the 1/2, 1/3 and 2/3 components of original frequency St=1.6 are measured.

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The sound radiated from an open end of a pipe, having a finite flange or outer pipe, was experimentally studied by measuring the sound pressure distribution in the pipe, in order to examine the theory of pipe-end corrections. For pipes with a flange of diameter ratio D/d>3, the pipe^end correction is close to the value an infinite flange. As the projection length of the flange becomes longer than l/D=1, it approaches the free radiation of a pipe without flange. For pipes covered with an outer pipe, the open-end correction takes the value of a flanged pipe for L/d<0.2, and that of a nonflanged pipe for l/L>2.

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To estimate the uncertainty intervals of hot-wire data, two types of errors, i.e., bias and precision, should be identified. In cross-wire or X-probe measurement, inevitable bias errors usually occur because of rectification (inherent insensitivity of hot-wires to the direction of an instantaneous velocity vector), the influence of high-order moments on a hot-wire response equation, and a finite separation between two wires, all of which cannot be neglected in measurements of high-intensity turbulence. In the present study, we have developed simple equations to estimate these inherent bias errors of hot-wire measurements for various flow conditions, i.e., arbitrary levels of turbulence intensity, correlation coefficients, etc.. In measurements of ordinary turbulent flows, the present error-analysis equations provide estimates of measurement errors as accurate as those obtained with a sophisticated computer simulation technique.

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A real-time method of measuring an unsteady flow rate employing differential pressure in a pipe has been presented by the authors. In this measurement method, a distance between two points measuring a differential pressure is shown to have great influence on the measurement accuracy of an unsteady flow rate. This paper clarifies a standard for designing the measurement distance of a differential pressure. Relations between a true pressure gradient and an approximated pressure gradient using the differential pressure are presented. From investigations in frequency domain, very simple inequalities on a measuring distance, which assure an accuracy of measurement, are derived. The standard of a measurement distance is examined by numerical simulations for high-frequency oscillatory flow. The results of this study are very useful for practical applications of the real-time method of measuring unsteady flow rate in a pipe.

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It is common for turbopumps of rockets to be operated in low NPSH conditions. Therefore, oscillation of propellant feed systems associated with cavitation is often encountered. If this oscillation is coupled with the structure of a rocket, longitudinal vibration referred to as "POGO" occurs. Regarding cavitating inducer instabilities, many studies have been conducted. However, it seems that studies of cavitating centrifugal pumps with an inducer for cryogenic fluids are few. In the present study, one aspect of the unsteady and dynamic characteristics of liquid oxygen centrifugal pumps was examined using power spectral methods.

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This paper describes the effect of impellers on a critical inlet flow angle for the onset of a diffuser rotating stall and on rotational speeds of stall cells. The experiment has been carried out using four specially designed impellers and a diffuser. The main results in this experiment are as follows : The critical inlet flow angle is independent of impellers and the predicting equation of that in the first report is useful for all impellers. The critical inlet flow angle is constant for all rotational speeds of the impeller. The onset of the rotating stall is independent of flow velocity at the diffuser inlet. The experimental equations of rotational speeds of cells are useful for all impellers. A predicting method of a critical discharge coefficient for the onset of the rotating stall is presented in this paper. The method is accurate enough for practical usage.

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In multistage axial compressors used for gas turbine engines, it is import ant to clarify unsteady phenomena such as surge and rotating stall. The purpose of this study is to develope a practical analysis method for both the surge and rotating stall in axial compressors. In this paper, firstly, some characteristics of the unsteady phenomena in axial compressors are summarized, derived from the measurments in test compressors. Secondary, a numerical method for the unsteady phenomena assuming incompressible flow is described. A feature of the method is solving the equations by Galerkin's method with the circumferential flow distortion expressed in the form of a high-order Fourier series. Finally, the usefulness of the method is examined by some results from a parameter-survey computation and by a comparison with the measured results in a 3-stage test compressor.

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The key problems of improving the performance characteristics of a multistage centrifugal compressor are an efficient conversion of dynamic energy into static pressure within the return passage and an improved matching with the downstream stage. To achieve these goals, a single-stage centrifugal compressor with a return passage attached upstream was first examined. The pressure ratio and the impeller efficiency were determined with varying the geometry of the return passage and the inlet swirl. The results were compared to those without a return passage. Detailed measurements of flow fields within the return passage were then performed. The cause of the performance decline and the optimum flow conditions are discussed. The usefulness of the one-dimensional analysis for a practical prediction of losses in the return passage is confirmed.

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Ocean energy has been paid much attention as one of the substitute energy resources for fossil fuel because it is abundant and clean. A pendulor type wave energy converter was invented by the project staff of the Muroran Institute of Technology where it has been studied since 1979. The maximum theoretical efficiency of energy absorption is 100% in regular waves. In the laboratory, it is proved that the best value of the wave power extraction is about 70% of the incident waves, by using two dimensional models driven by sinusoidal regular waves. The second prototype system has been investigated at the coastal site of the Muroran Port since November 1985. Its maximum efficiency is about 70% for irregular waves. The results of the experiment show that the efficiency is better than any of the other types. In addition, several good results are obtained by the use of a splitter and a reflector in the experiment of the precautions against the unusual high waves.

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The flow in various types of suction casings of multi-stage centrifugal pumps is investigated experimentally, and is compared with the suction performance. The results show that the symmetrical bend type casing has poor suction performance because of distorted inflows at the impeller inlet section, while better suction performance is obtained from the volute type casing which has fairly good flow distribution. It is clarified that the suction performance is affected by the velocity distortion, especially in the circumferential direction, and the incipient cavitation is related with the local incidence angle of the impeller blade.

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The method of predicting incipient cavitation based on conventional flow analyses is presented for estimating the suction performance of centrifugal pumps with distorted inflows. Three-dimensional potential flows through two type suction casings are analysed and compared with experimental results. In symmetrical bend type casing, nonuniform outlet flow of the casing is able to be predicted by suction casing flow analysis ; but the correction of pre-rotation should be considered to get a successful prediction for the case of the full volute type casing. The prediction of incipient cavitation NPSH agrees with the experimental results when the impeller flow is analysed, considering the non-uniform inlet flow of the impeller.

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A theoretical analysis of passage and exit flow of a two dimensional logarithmic impeller with leading edge cavitation by using the singularity method is performed. In the wide parametric calculation, the flow features of impeller passage such as the cavity characteristics and the distributions of the relative velocity, and the static pressure are clarified with the flow rate, the blade number and the blade angle. And in the case of both back and face cavitation, the distributions of the static pressure, relative flow angle and the slop velocity at the impeller exit are also clarified with the blade number and the blade angle. And further, the changes of the slip factor and the impeller efficiency by the cavitation are shown to be determined from the simple formula. Finally, a comparison of the present calculated results with the experimental data and former calculated results is made.

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This paper deals with an experimental study on the unsteady cavitation performance in the convergent flow of an oil hydraulic poppet valve. Experiments are carried out under two kinds of flow conditions : one is an unsteady flow in which the valve inlet pressure, p₁, takes the form of a trapezoid varying with time and keeping the outlet pressure, p₂, constant ; the other is the flow in which the former p₁ and p₂ are interchanged, respectively. It is found that as the absolute value of the rate of pressure change dp₂/dt increases, the incipient cavitation number, k_ci, shows a tendency to decrease, and the desinent one, k_cd, shows a tendency to increase under all geometric parameters in this test. As the absolute value of dp₂/dt further increases, the hysteresis between k_ci and k_cd becomes larger for each combination of the valve and valve seat.

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An experimental study was performed to determine if the heating of a cylinder inserted to disturb a flat plate turbulent boundary layer can affect the dissimilarity between heat and momentum transfer reported previously for a case with an unheated cylinder. In the experiment, the cylinder was maintained at the same temperature as the wall surface. From the measurement of the wall heat transfer coefficient, the effect of the dissimilarity of the boundary conditions between velocity and temperature fields was found to be small. Simultaneous measurement of streamwise and normal components of velocity fluctuations and of temperature fluctuation was also made. Intensification of hot outward and cold wallward interactions due to the disturbance given by the cylinder were found to be a major cause of the dissimilarity between the heat and momentum transfer.

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This study aims at the fundamental research to experimentally clarify performances of heat and flow fields using water in a vertical heated straight circular tube in the Reynolds number region below 2000. The experiments were caried out using a brass tube of 22 mm inner diameter and 1500 mm length which was heated by nichrome wires under a constant heat flux condition from the tube outside. The tube was surrounded by heat insulating layers to avoid heat loss. It was reported that under the condition of a smaller wall heat flux a heat-transfer deterioration was observed due to a decrease of the fluid temperature gradient at the inner tube wall caused by the buoyant force. It was also found that, even in the Reynolds number region of 500 through 800, in the case of a larger heat flux, a heat-transfer enhancement was observed due to a velocity fluctuation caused by the appearance of an inflex poiot of the velocity profile owing to the strong buoyancy force effect near the wall.

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A superposition approach can be used for predicting cooling performance of IC packages mounted on a printed wiring board. This paper shows a calculating model of the temperature distribution in the thermal wake of a single IC package on a board. The thermal diffusion layor behind a point heat source spreads three-dimensionally. And the temperature distribution in the cross section of the layer is expressed by a cubic expression of the radius in the cross section. In the case of a heated package, the boundary layor on the package is assumed as the linear heat source. The integration of the temperature distribution due to the points in the linear heat source gives the temperature distribution of the wake of the package. The thickness of the diffusion layer was measured experimentally and expressed as a function of the distance from the package.

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This report deals with the heat transfer augmentation of an axisymmetric impinging jet using a perforated plate which is installed in front of a target plate. The effects of the diameter (d) and pitch (p) of the holes in the perforated plate, and the spacing between the perforated and target plates on impinging jet heat transfer have been experimentally studied. The obtained results demonstrate that the effects of the present perforated plates on heat transfer augmentation are maximum inside the potential core region. When a perforated plate with a pitch-to-diameter ratio of 2 (p/d=2) is installed at a distance from the impinging plate less than twice the hole diameter (2d), the heat transfer coefficient at the stagnation point on the target plate becomes maximum and goes up to about 2.3 times as large as that in the case without a perforated plate. Under the appropriate conditions of the perforated plate, the mean heat transfer coefficient averaged within some distance from the stagnation point is larger than that without the perforated plate, even when the averaging distance is longer than 1.5 times the nozzle-diameter.

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Frost formation on and choking of evaporators are perplexing problems in heat-pump systems using ambient air as the heat source. In the present study, heat-and mass-transfer, frost formation and defrosting of single row cooled-tubes were investigated experimentally in a uniform humid air flow, an impinging air jet, and a fluidized bed with a multi-slit distributor and a static-bed height of 10 mm, respectively. The heat transfer performance for an impinging jet decreased with time, because of the frost formation. As for teflon coated tubes in the present fluidized bed using glass beads of 0.92 mm in diam., it was found that non-frost operation is possible under comparatively wide conditions of heat flux and superficial velocity, and that the heat transfer performance is about five times that for the uniform air flow.

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A forced-air-cooled heat sink with new enhanced fins was developed. The fin has many perforations and is bent to form a trapezoidal shape. The fin was enhanced in heat transfer by a breathing effect, a phenomenon by which the fluid is injected and sucked through the trapezoidal perforated fins. The thermal conductance of the heat sink at the same pumping power was about 1.6 times that of a similar heat sink with conventional plain fins, and also about 3 times at the same Reynolds number. A heat sink with the new enhanced fins designed for practical use was also shown.

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On heat exchangers with frosting, the characteristics changes with time due to the growth of a frost layer, which depends on frosting conditions. In this paper, the emperical correlations for initial conditions needed to predict frost formation based on the structural model were presented and thay enabled to predict the frost growth without using any experimental data under various frosting conditions. The difference in characteristics between parallel and counter flow type heat exchangers with frosting has been studied experimentally and theoretically. It was found that with growing of a frost layer, the average thermal resistance on counter flow type became larger in comparison of that on parallel flow type and the temperature efficiency for counter flow type gradually approached that for paralell flow type.

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Laminar heat transfer mechanism in separating and reattaching flows has been numerically studied by simulating flow and heat transfer behind backward-facing steps. As a result of systematic numerical experiment, detailed relations between the heat transfer characteristics and the principal parameters related to flow and geometry were obtained. An important finding is that the distribution of the local Nusselt number is strongly dependent upon both the Reynolds and Prandtl numbers and the location of the peak in it does not necessarily correspond to the point of the flow reattachment.

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An experimental study on the enhancement of heat transfer on a flat plate turbulent boundary layer disturbed by a circular cylinder with a two-dimensional slit placed along the diameter was performed. At the cylinder position, the thickness of the boundary layer without the cylinder was nearly equal to the cylinder diameter, and the cylinder was placed at a height of half the diameter of the cylinder above the plate. The heat transfer performance was better than that of a circular cylinder without a slit in the case of low free stream velocity.

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The purposes of this report are to establish the measuring systems for liquid holdup and to obtain the relationship between the flow and the mass-transfer coefficients for gas continuous two-phase flow in packed beds. Liquid holdup existing in packed beds was obtained by using the method of neutron attenuation ad a correlation for liquid holdup was presented as a function of the Reynolds number and the Galilei number. Liquid-to-particle mass-transfer coefficients for gas continuous two-phase flow depended on the liquid holdup, and the modified correlation for mass-transfer coefficients was obtained by modifying the Reynolds number and the Sherwood number, considering the actual liquid velocity in packed beds and the ratio of the mass-transfer area to the sectional area of flow.

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The unsteady state heat conduction of superconductors (Nb₃Sn and V₃Ga) was numerically studied. For this purpose, the non-linear successive over relaxation method has been applied. In this way, the boundary conditions of non-linear heat conduction, which contain thermophysical properties varying with temperature, are considered. The numerical results of the unsteady state heat conduction of these superconductors show different temperature distributions compared with normal heat conductors. According to the physical interpretation of heat conduction phenomena on a superconductor using the numerical analysis, the unsteady state temperature distributions are determined to the two solid media having different thermophysical properties in a lower transition temperature region and in a higher transition temperature region.

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The movement of the condensation liquid on a vertical smooth tube in three modes (heave, sway and roll) of sinusoidal vibration were studied experimentally in order to analyze the effect of motion on the heat transfer performance for a moving ocean platform such as the OTEC plant. The appearance of moving liquid was photographed by a video camera and the thickness of liquid film at the side of tube measured by the method using the dark and light difference of photographed images. The effect of heave motion on the film thickness was not detected, but the sway and roll motion resulted in the periodic change in the amount of film thickness following the tube motion. The dependencies of the maximum thickness and its generated position upon amplitude and frequency were discussed.

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Experimental analyses were performed for the results of flow visualization as shown in the 1st report, in which saturated steam bubbles of approximately 10 mm in diameter were injected into a quiescent subcooled water environment. The patterns of bubble collapse were analyzed through photographs selected from a motion picture film and presented as the instantaneous bubble diameter vs time. An upward motion was imparted to the bubbles by bouyancy, and owing to heat transfer and condensation at the liquid-vapor interface, the bubbles diminished in size as they ascended. The time variations of the bubble diameter and position were determined from a detailed analysis of the photographs. The experiments were performed for pressure levels from atmospheric to 10⁶ Pa and for temperature differences between the saturated steam and water for subcooled 10-70°C. From these, results were deduced for the time for bubble collapse, and average heat transfer coefficient. Dimensionless correlations desired by Brucker et al, were assured for a variety of the aforementioned quantities.

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Complete condensation of nonazeotropic binary mixtures of R11-R113 refrigerants is experimentally studied. The test apparatus consists of two concentric horizontal tubes, with the vapor mixture flowing in the inner tube and the cooling water in the annular space in the countercurrent direction. The composition and the mass flow rate of the binary-component mixture are systematically varied. Through the measurement of the local temperature of the wall, the cooling water and the vapor along the tube axis, the axial distribution of the local heat transfer coefficients are obtained. An empirical equation is derived to correlate condensation heat transfer performance.

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As for the preexisting vapor-nuclei trapped in the cavities on a solid surface, the minimum superheat required to activate them is determined by the critical nucleus, where the radius of the curvature of the liquid-vapor interface reaches a minimum. In the present paper, the thermodynamic analysis is used to investigate the stability condition of preexisting vapor nuclei and to make clear the physical meaning of the critical nucleus. The thermodynamic consideration shows that preexisting nuclei can hold the thermodynamically-stable equilibrium state when the curvature of the liquid-vapor interface increases due to increased volume. Further, the stability of preexisting vapor nuclei trapped in a doubly reentrant cavity under large subcooling is examined concretely for freon R-113, and the temperature overshoots which occur during the inception of nucleation on enhanced boiling surfaces are estimated.

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An analysis is made for two-dimensional, steady-state film boiling heat transfer from a finite-size, isothermal, horizontal plate facing downward to a stagnant saturated liquid, including the effect of the plate edge and contribution of radiation heat transfer. The laminar boundary-layer equations for the flow of vapor beneath the heated plate are solved using an integral method and the solution is obtaind analytically. Numerical results of the solution are examined for saturated water at atmospheric pressure. It is shown that (1) the vapor film has a maximum thickness at the center of the plate and that its thickness decreases towards the edge. The vapor film becomes thicker with an increase of the plate width or of the degree of superheating, (2) the convection heat transfer is strongly affected by the plate width, and (3) the radiation heat transfer and its contribution to the convection heat transfer can not be neglected when the degree of superheating is large.

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To explain the negative temperature dependence of heat-transfer coefficient in a column-like boiling regime, where a vapor column is formed just behind a nozzle outlet, simplified model experiments were carried out. Optical observation of R113 liquid behavior floating on a flowing water surface gave the following results. R113 liquid on the water surface alternatively could take three states, such as spheroidal drop, lens and continuous thin film. When the temperature difference between water and saturation temperature of R113 was raised, the appearance time of the spheroidal drop state became longer and the average thickness of the lens or continuous thin film states with shorter appearance time increased. Heat transfer to evaporating R113 liquid was enhanced in this order of three states. These results lead to a lower heat-transfer coefficient at a higher temperature difference.

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The vaporization behavior of a single droplet impinging on a heated surface which was coated with ceramics such as alumina, magnesium zirconate and zirconium oxide was studied. This is the extension of the previous study on a vaporizing droplet on a solid surface of ceramics. The lifetime curves for some pure liquids were measured at a surface temperature up to 1100 K. We observed in detail the vaporization process of a droplet using a 16 mm high-speed motion-picture camera and high-speed video camera. It should be stressed that the ceramic-coated surface brought a wide temperature range yielding minimum vaporization times and short lifetimes in spite of its thinly coated layer, owing to its low-thermal conductivity and characteristic surface.

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This study has been undertaken to clarify the motion of condensate drops on a rotating horizontal tube under dropwise condensation. It is difficult to clarify the behavior of condensate drops on a condensing surface, because of their constantly changing weight and shape. Therefore, in air, the behavior of a water drop with a constant weight on a rotating dry tube was investigated using a video-tape recorder. Moreover, the velocity and the location of a falling drop on a rotating tube were calculated. The effect of the rotating speed on the behavior of a water drop was clarified.

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Radiative heat transfer in the furnace of a supercritical steam power plant is analyzed by using "Radiative Energy Absorption Rate Distribution". The temperature distribution of the water wall is calculated by taking the thermophysical properties of water into consideration. These calculated values correspond well to the measured values.

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Measurements are made of the gain of a CO₂ gasdynamic laser (CO₂ GDL) utilizing the products of continuous combustion of liquid fuel C₆H₆ and gaseous oxidizer O₂. Soot-free, high-pressure, stable combustion is realized using a rocket-engine-type combustor. It is found that the combustion products can become active media for a CO₂ GDL, and a maximum small-signal gain of 0.6 m^-1 is obtained at the combustion temperature of 1200 K and the pressure of 2.54 MPa. The results are compared with earlier experiments on C₆H₆-Air GDLs.

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An experimental study was made of the evaporation of the linear array of hydrocarbon droplets suspended on quartz threads in a uniform stream of air. The effect of inter-droplet distance on the rate constant of evaporation was extensively studied under various ambient conditions. The interaction between the neighboring droplets in the evaporation process was discussed on the basis of the profiles of vapor mass fraction, velocity and temperature around a droplet, which were measured with the application of the laser Rayleigh scattering technique, LDV and a fine thermocouple respectively. The results showed that the rate constant of evaporation of the downstream droplet decreased with a decrease in the inter-droplet distance. The limit of inter-droplet distance which caused the interaction showed a maximum as a function of the Reynolds number. It is most probable that the decrease of rate constant of evaporation of the downstream droplet was caused primarily by the variation of the vapor concentration around it.

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This paper presents an experimental study being aimed at revealing the ignition assistance effect of a hot surface in an alcohol-fueled diesel engine and its mechanism. A single shot of spray was injected into a motored diesel engine. Ignition lag was measured and was split into two regimes, physical lag and chemical lag, by applying a statistical technique presented by S. Kumagai. High-speed direct photographs were also taken. The dependence of those ignition lags were classified into three regions on their Arrhenius plots. In lower hot-surface temperatures, the ignition lags decrease exponentially with increasing the hot-surface temperature. In higher temperature regions, the ignition lags tend to have constant values, passing through the transient region. By combining the high-speed photographs, it is suggested that the hot surface does not initiate flame propagation, but supplies heat to assist the spontaneous ignition as the assistance mechanism.

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