Experimental investigations on the unsteady cavitating flow around an elliptic cylinder of axis ratio 3 : 1 were carried out for several angles of attack and a wide range of cavitation numbers. The flow characteristics were studied by measuring the fluid force and the pressure fluctuation. Under non cavitating conditions, a dramatic change of flow state was observed in the critical Reynolds number regime. This change of flow state has a great influence on the unsteady characteristics of cavitating flow.

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Experimental investigation of the flow around an elliptic cylinder of axis ratio 3 : 1 was carried out for several angles of attack and a wide range of Reynolds numbers. The flow characteristics were studied by measuring the fluid force and the surface pressure fluctuation. In the critical Reynolds number regime, a discontinuous change of flow state was observed. This change was accompanied by the hysteresis effect. The fluid force and the pressure fluctuation decreased markedly in the critical flow state.

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Flow patterns and wall shear stresses in periodically grooved channels were studied in the transitional flow regime. In order to examine the effect of groove length, we employed three different channels. It is found that self-sustained flow oscillation occurs at a lower Reynolds number as the groove length is increased. The flow instability arises from Tollmien-Schlichting waves triggered by a shear layer between the bulk flow and groove flow, which is confirmed by numerical simulation. A significant increment in the wall shear stresses is identified after the onset of flow instability, and mass transfer is enhanced.

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This paper describes the effect of the spacing between two adjoining circular cylinders on the flow around two-dimensional circular cylinders supported by wires. The experiment was carried out in an N.P.L. blow-down unit wind tunnel with a working section of 500×500×2000mm, at the Reynolds number 9.4×10³. The frequency of vortex shedding from the circular cylinder, displacement of the vibrating circular cylinder, and the time-mean and fluctuating surface pressure distributions on the circular cylinder were measured. The present results were compared with those for the case of fixed support Vortex shedding from circular cylinders occurs in the range of spacing ratio S/D≥2.3. The variations of Strouhal number, displacement, surface pressure distributions, drag coefficient, lift coefficient, fluctuating drag coefficient and fluctuating lift coefficient with the spacing ratio were obtained.

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In this paper we describe the effect of spacing between two adjoining circular cylinders on flow around three rows of two-dimensional circular cylinder bundles supported by wires. The experiment was carried out in an N.P.L. blow-down-type wind tunnel with a working section of 500mm×500mm / 2000mm and with the Reynolds number of 9.4×10³. The frequency of shedding vortices from the circular cylinder, displacement of the vibrating circular cylinder, and the time mean and fluctuating surface pressure distributions on the circular cylinder were measured. And the results were compared with those for the case of fixed support. Consequently it was found that (i) shedding vortices from circular cylinders exist in the range of spacing ratio S/D≥3 for the first row, S/D≥2.3 for the second row and S/D≥2.0 for the third row, (ii) the fluid elastic vibration occurs in the range of S/D<2.O for the first row and S/D<2.3 for the second row, though it does not occur for the third row, and (iii) the variation of fluctuating drag coefficient and fluctuating lift coefficient corresponds to that of displacement of a vibrating cylinder.

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The characteristics of axial flow around a circular cylinder with a forward facing step in a wind tunnel have been experimentally investigated by use of pressure measurement and flow visualization in the range of the Reynolds number, 10⁵≤Re≤3.8×10⁵ based on a diameter of the outer circular cylinder. The experiments are carried out for the ratio of a forward facing step distance, Sx/r_o, which varies from -0.044 to 0.35, where r_o is the radius of the outer cylinder. The pressure coefficient, Cp, on the front step face shows a very low value of -2.5 for, Sx/r_o=0.2. The axial drag coefficient of the cylinder, C_D, is about 0.20, which is a fourth part of the drag coefficient of the flat face cylinder without a forward facing step. The flows around the cylinder model were visualized by the smoke method and the oil film, where the diameter ratio of the inner circular cylinder and the outer cylinder, d_i/d_o, is about 0.9.

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Pressure drop was measured for air-water two-phase flow in a vertical capillary tube. Inner diameters of pipes used were 1mm, 2.4mm and 4.9mm. The directions of flow were both vertically upward and downward. Several correlations of pressure loss in two-phase flow, which have been proposed so far, were examined to determine whether or not they are useful for a capillary tube. As a result, it was clarified that those correlations cannot predict the data with high accuracy, especially in the intermittent flow region. Thus we proposed a new. correlation in which the expansion loss of water flow from water film around a large gas bubble to a water slug is taken into consideration. It shows better agreement with the experimental data.

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One solution method for an inviscid flow field of a two-dimensional Darrieus-type runner in an arbitrary-shaped duct and a draft tube is proposed in the present paper. This computation consists of two stages. As the first stage, the flow through the duct is analyzed by a panel method with vortices distributed on the duct walls and the stream function and velocity potential are obtained at any position in the physical plane. Using these values the flow field is transformed to the reflected plane of flow with parallel walls as the stream function on the wall becomes constant. The induced flow due to bound and released vortices of the Darrieus blades is analyzed by the image method in the second stage. The evaluated Darrieus blade characteristics from the measured data with this solution and the calculated flow distortions due to the blade behavior are shown and discussed for ducts of various shapes.

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Measurement of drag reduction and frequency analysis of the wall pressure fluctuation in pipe flow are carried out using dilute polymer solutions and aqueous detergent solutions in order to discuss the correlation between drag reduction and pressure fluctuation. Frequency analysis indicates that the power spectrum density of the pressure fluctuation of dilute polymer solutions is greater in the low-frequency region and less above 30[Hz] than that of water (solvent). Moreover, the level of pressure fluctuation in dilute polymer solutions is on the whole greater than that in water.

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Much uncertainty exists in the numerical simulation of rarefied gas flow because of the unreliable models of boundary condition on a solid surface. In order to construct a new model, we must obtain much information on the micro-scale dynamics of gas-surface interaction. The behavior of a Xe gas molecule which collides with the clean Pt(111) surface of a very thin film is computed using the classical molecular dynamics method. The energy transferred from gas molecule to surface molecules is analyzed. The energy distribution is almost normal, and varies with the position of collision in the surface lattice. The average of the transferred energy agrees quantitatively with the results of soft cube model. The wall temperature exerts an effect on the deviation of the transferred energy, and not on its average. We developed a very simple scattering model with 'multi-stage' which can reproduce the very distorted distribution of velocity of gas molecule immediately after the first collision.

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The actual time-accuracy of several time integration schemes is investigated for the unsteady compressible Euler equations. Runge-Kutta, implicit-approximate factorization, and implicit iterative schemes have been applied to several unsteady problems of transonic flows over a pitching airfoil. The flux difference splitting scheme of Roe with the MUSCL algorithm is used for determining numerical fluxes. The Runge-Kutta scheme produces little numerical error in its stable limit. However, no advantage of its third-order accurate form over its second-order accurate form can be found. The Beam-Warming scheme with approximate flux Jacobians is essentially first-order accurate in time and is not suitable for unsteady flow simulations. In order to preserve the accuracy of the numerical solutions, higher-order time-accurate forms as well as Newton-type iterations are necessary for the implicit time integration scheme.

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Quasi-streamwise vortices observed in near-wall turbulence arranged in a typical zigzag pattern in the streamwise direction are investigated by analyzing the flow field of data bases obtained by both high-resolution LES and numerical integration of the parabolized Navier-Stokes equation for channel flow, focusing attention on the mechanism of self-sustenance and regeneration. It has been revealed that quasi-streamwise vortices are inherently self-sustaining. Namely, they achieve their streamwise vorticity by stretching the spanwise vortices of mean flow by means of self induced velocity fields. The analysis of the regeneration mechanism also shows that the quasi-streamwise vortices have inherent potential to regenerate themselves using their own velocity fields. The approximate quasi-three-dimensional simulation based on the parabolized Navier-Stokes equation confirms the conclusions of the analysis of the LES data base.

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A wavelet analysis using the Morlet wavelet is applied to show the existence of low-frequency modulation in the velocity fluctuation in the turbulent vortex street wake of a circular cylinder at a Reynolds number of 5000. The central frequency of the low-frequency modulation f_m is 1/30-1/20 times the frequency of vortex shedding from the circular cylinder. This value of f_m is the same as that obtained by previous investigators at much lower Reynolds numbers in the range 80∼1340. The structure in the wake which is responsible for the low-frequency modulation is suggested to be a large-scale irregularity in the vortex street. It is shown that the modulus of the wavelet coefficient is a useful means of studying the amplitude modulation of the Fourier component of a signal.

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Measurements of the turbulent velocity field have been performed in a newly designed low-speed two-dimensional mixing layer facility Mean and fluctuating velocity in the streamwise direction are measured by an I-type hot-wire anemometer, and the dissipation rate is evaluated from the time derivative of the fluctuating velocity signal based on the Taylor hypothesis and under the assumption of local isotropy of turbulence. The moments of velocity fluctuation up to the third order agree well with previous experiments and DNS, when normalized by the local turbulence velocity scale, the region of self-similarity in terms of the relative turbulence structure is found to be larger than the conventional definition of the global self similarity region where the turbulence velocity scale no longer varies in the streamwise direction. The dissipation rate can also be well correlated with the recent DNS result, when the Taylor micro length scale and local turbulence velocity scale are chosen as the characteristic length and velocity scales, respectively.

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An investigation of turbulence structure with the secondary flow of the second kind in a trapezoidal open channel is very important in basic hydraulics and river engineering. In this study, a numerical analysis has been carried out to develope turbulent flow in a trapezoidal open channel with three kinds of bank angle. An algebraic Reynolds stress model coupled with a boundary-fitted coordinate system was abopted in order to predict Reynolds stresses precisely. Calculated results were compared with the experimental data available. It has been pointed out from the experiment that velocity-dip, which means that the maximum velocity appears not at the free surface but rather just below it, is not observed in a trapezoidal open channel. The calculated results of streamwise velocity show that the maximum velocity exists at the free surface. For this reason, the present method predics this feature. Furthermore, the secondary vectors of the calculated result are in good agreement with those from the experiment, which proves the validity of the present method. Near the free surface, the secondary flow direction in a trapezoidal open channel is opposite to that in a rectangular open channel. The orign of this difference between the cross sections is examined by evaluatidng the production term of the streamwise vorticity equation.

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The three-dimensional vortical structures in a rectangular jet were determined by measuring the phase-average fluctuating static pressure, and the characteristics of the structure were discussed. The experiments were carried out for an air jet issuing from a sharp-edged rectangular orifice. The jet was excited in the interaction mode, in which the stable interaction of vortices occurred. The phase-average pressure was measured over the flow field with a static pressure probe. The three dimensional contours of phase-average pressure provided useful information on complicated vortical structures. The structures were characterized by stretching, splitting and cut-and-connect of vortices. The results suggest that the direct measurements of fluctuating static pressure are very useful for detecting three-dimensional complicated vortical structures.

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A doublet flow or a coaxial flow consisting of injection and suction flow, which is proposed for the purpose of diffusion control of a circular jet, was experimentally examined. In order to clarify the behavior of such flow, the correlations of fluctuating velocity in the streamwise and transverse direction were measured and the flow visualization technique was also used. It was clarified from these experiments that as the suction velocity increases, diffusion of the circular jet is promoted because the scale of vortical structure in the shear layer becomes large due to the strong shear stress. It was found from the results of the cross correlations of fluctuating velocity that asymmetrically ejected vortices exist and contribute strongly to diffusion of the jet. Furthermore, this phenomenon of asymmetrically ejected vortices moves gradually upstream as the suction velocity increases.

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The direct simulation Monte Carlo method is applied to the study of the structures of supersonic jets through a thin circular orifice. Three cases with different Knudsen numbers Kn are investigated, based on the stagnation conditions and the orifice diameter, 1/Kn=50, 500, and 2500. The pressure ratio is 50 in all cases. The Mach disk and barrel shock are not observed at all in the case of 1/Kn=50, but they appear slightly at 1/Kn=500 and are clearly observed at 1/Kn=2500 in the density, velocity and temperature profiles. The Mach disk is obtained at the expected axial location for 1/Kn=2500, which demonstrates that our DSMC calculation is reasonable. The DSMC results are also compared with experimental results obtained by a mass-sampling technique and qualitative agreement is recognized in the broadening of the barrel shock with decreasing density.

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This paper describes the results of an experimental study concerning the frequency components of flow fluctuation in double coaxial pipe jets. We examined the effects of velocity ratio, outer pipe length and lip thickness of the inner nozzle on the flow structure and velocity frequencies. It was found that, for velocity ratios u^^-_i/u^^-_o &lsim; 0.5, the velocity fluctuation is mainly composed of the frequency of the vortex street whose excitation depends on the outer pipe length, and the values of the Strouhal number St_Lbased on the outer pipe length are constant at 0.64N (N=1, 2, 3...). u^^-_i/u^^-_o &gsim; 0.5, however, the velocity fluctuation frequency is due to the alternate shedding of lip wake vortices in the inner mixing regions, and behaves in such a way that the Strouhal numbers St_bi, based on the lip thickness of the inner nozzle are constant at about 0.2 for any outer pipe length of the jets.

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Measurement of the local skin friction coefficient and re-examination of the low-Reynolds-number effect are made in a zero pressure gradient turbulent boundary layer. The momentum thickness Reynolds number R_θ ranges from 840 to 6220. The wall shear stress τ_w, is determined from the direct measurement method using a floating element device in a flow field where the two-dimensionality of a boundary layer is examined thoroughly. From the present results of C_f, an empirical formula for C_f and R_θ is proposed and proven to have good accuracy. For the present R_θ range, a log region with a constant χ exists. The additive constant C, however, varies with the Reynolds number. The magnitude of the wake parameter maintains a constant value of 0.62 for R_θ >; 5000. The effect of R_θ on all the turbulent intensities is felt within the sublayer. Both the peak and its location for (uv)^^-/u²_τ increase with R_θ.

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The thermoacoustic effect is a nonlinear phenomenon produced by finite-amplitude oscillation of air in a closed tube. This effect generates a steady temperature distribution along the tube axis and causes heating and cooling of the tube wall at loop and node points of standing waves. Recently, the thermoacoustic effect has attracted the interest of many researchers, because it can be applied to the development of refrigerators that use a substitute for Freon. For practical design of the refrigerator and improvement of its efficiency, a detailed analysis of the thermoacoustic effect is required. Theoretically, the existence of the thermoacoustic effect has been analyzed by the perturbation method, and the results obtained in the case of small-amplitude oscillation agreed with the experimental results. However the experimental results in the case of finite-amplitude oscillation did not coincide with the theoretical results. This paper describes the numerical analysis of the thermoacoustic effect induced by finite-amplitude oscillation in an air-filled tube. The calculated results in the case of finite-amplitude oscillation with shock wave propagation show that the time-average of nonlinear term of the energy equation, which corresponds to steady heat flux, increases as the oscillation amplitude increases, and then the cooling effect vanishes.

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A strong sound field produced in an air-filled tube generates steady pressure distribution, acoustic streaming and thermoacoustic effect as nonlinear phenomena of the finite-amplitude oscillation of air column in the tube. One of the applications of these phenomena is the promotion of heat convection in an air-filled duct, When a sound field is superimposed on a Taylor-Benard convection generated in a horizontal duct, coupling of acoustic streaming and thermoacoustic effect with the convection is experimentally observed as the change in structure of the convection field, and it promotes heat transfer. This paper describes a quantitative analysis of the coupling phenomena using a numerical method. The calculated results show the variations of velocity, acoustic Reynolds stress and temperature distributions in the Stokes layer with different values of temperature difference between the upper and lower walls of the duct. With these results, the effects of coupling of acoustic streaming and thermoacoustic effect with convection are discussed.

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This paper concerns a numerical simulation of a flow of reactive multicomponent gas through a packed bed consisting of catalyst beads which is used in various chemical apparatuses such as a fuel cell reformer. The aim of this simulation is to clarify the effect of change of area along the channel on the flow pattern of each component, in order to investigate the deposition of carbon for the reformation of hydrocarbon -steam mixture in the reformer. It is found that the deposition is apt to occur near the throat of the channel and its probability is higher for a propane-steam mixture than for a methane-steam mixture.

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This paper deals with a fundamental study on the control problem of distributed parameter and nonlinear flow fields using a high-performance supercomputer as a controller. A state observer is proposed as a basic element of the control system to estimate the complete state from th mathematical model and partial measurements. A SIMPLER-based flow simulation algorithm is used as the mathematical model of the system. The error of the numerical solution evaluated by comparison with the measurement is fed back to the mathematical model to reduce the discrepancy. The adoption of this feedback loop distinguishes the state observer from ordinary flow simulations. With this feedback loop the computational result may converge even for unstable flows with fluctuations. A numerical simulation has been performed for a turbulent flow through a square duct to confirm the validity of the present state observer. A real flow is simulated using a standard numerical solution of a developed turbulent flow. Appropriate choice of the proportional feedback gain accelerates the convergence in the simulation by a factor of 60 and reduces the error in estimating the perturbation velocity component by a factor of 0.5 in comparison with he ordinary flow simulation without a feedback loop.

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The effect of micron-sized roughness in the leading edge region on a swept wing boundary-layer transition is examined experimentally in detail. By applying sound waves from a loud speaker, sound receptivity to turbulent transition is also investigated. Results showed that such a minute roughness element (κ=45μm in height, 1mm in diameter, κ/δ=0.23) placed at χ=40mm resulted in early transition. In the case that no transition enhancement was observed in the presence of a single roughness element, early transition also occurred with sound excitation. Low frequency disturbance f₁ responded strongly to the sound frequency, in particular, to the direction of the sound waves. Critical spacing of roughness elements where the transition is amplified the most seems to exist in the range of λ/δ≒1.3. It is also noted that no enhancement of transition occurs when the roughness element is placed beyond 20% of the chord length.

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Two types of rubber extrusion analyses from a capillary rheometer (Monsanto Processability Tester) were conducted and calculated results were compared with the experimental data to verify the applicability of these analyses. Analyses were conducted under the condition of two-dimensional axisymmetric incompressible viscous flow. One of the analyses used in this paper is unsteady finite element analysis using marker particles and the other is steady finite element analysis with the streamline integration method. The material model used in both analyses is the power-law model. Calculation results of the unsteady analysis using marker particles were in good agreement with the experimental ones even at high flow velocity. Calculation results of the steady analysis with streamline integration method were poor at high flow velocity. From the calculated results, it was found that it is not always sufficient to use the power-law model for the quantitative analysis of the rubber dieswell from MPT.

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A function which represents the surface tension of a liquid based on the configuration of a droplet is obtained theoretically. Behavior of a droplet of liquid is governed by a nonlinear differential equation which can be solved numerically by setting its initial condition and surface tension. In order to solve the inverse problem of this equation, a formal solution is suggested as a series function, and a norm on the function space of droplet configurations is defined. Under the measure of this norm, a sequence of coefficients of the formal solution is determined from the observed droplet configuration. The inverse function of which variables are the sequence of coefficients that represents a drop configuration is obtained by using potential theory on the basis of the analytical representation of droplet configuration. It is also shown that convergence of the inverse function of finite series is sufficiently good for practical use.

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We have devised a new method for tip clearance measurement which does not require an actuator to move the discharge probe. The applications of this method and its characteristics were investigated, and tip clearance measurements were attempted. As a result, it was found that UV irradiation was indispensable for obtaining a constant discharge voltage in the range of 98kPa∼196kPa. The discharge characteristics varied with pressure, but a linear relationship could be obtained. The discharge characteristics varied with the shape of the rotor. Hence, this factor must be checked prior to measurement. The probes produced were not affected by the peripheral velocity of up to 80m/s. Measurement accuracy using a core-type probe was within ±0.05mm, and with a cylinder-type was within ±0.lmm. The cylinder-type probe was able to measure the tip clearance up to a peripheral velocity of 270m/s.

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To date, experimental studies of the flow in logarithmic spiral curved diffusers have been carried out under various conditions in order to clarify their characteristics and to improve their performances. In this study, effects of the existence of a guide vane and the variation in logarithmic spiral angle on the pressure distributions along both diffuser walls, the velocity and vector distributions in a curved diffuser, and the diffuser efficiency are clarified. As a result of this study, the following became clear. The diffuser efficiency was improved for all logarithmic spiral angles when a guide vane was interposed in the curved diffuser, and the improvement in the diffuser efficiency was enhanced as the logarithmic spiral angle β was made large. In the range increased of values for which this experiment was performed, consequently, a desirable diffuser efficiency could be obtained over a wide range of the logarithmic spiral angle β as compared with the result for the case in which a guide vane was not interposed.

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Noise in compressor stages with two vaned diffusers and a stage with one vaneless diffuser are measured. The overall noise level and the blade-passing frequency (BPF) component level in the vaned diffuser stages are higher than those of the vaneless diffuser stage. The difference in the BPF components of the two types of diffuser varies with the rotatinal speed of the impeller. Under certain conditions, the large noise which the BPF component is extremely high and sounds like a whistle is observed. Measurements of pressure fluctuation in the vaned diffuser passage show a standing wave in the flow passage, and so the loud noise is considered to be caused by resonance in the vaned diffuser. The resonance frequency is affected by the diffuser vane shape.

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In this study, entry waves produced by high-speed trains which enter a tunnel were numerically investigated. The equations of the one-dimensional, unsteady and compressible flow with mass removal in which the area of a tunnel is dependent on the time and distance were numerically solved by the method of characteristics. The calculations were performed for trains with various nose shapes in the case in which the speed of the train was 300km/h, and the effects of the nose shape of the train on the entry waves were quantitatively clarified. As a result, the optimum condition of the nose shape which forms the entry wave with minimum pressure gradient was shown.

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Macrolayer thickness at critical heat flux was measured for various liquids in the pressure range of 0.05MPa to 0.35MPa for upward and vertical disk heaters of 20mm diameter. Macrolayer thickness is determined based on the energy balance relation q_CHF=ρ_lH_fgδ_l·f, with measurements of the critical heat flux and the detachment frequency of vapor masses (coalesced bubbles) completely covering the heating surface. The correlation of macrolayer thickness proposed in the 4th report of this series by Kumada and Sakashita [Trans. JSME, 58-552 (1992), 2505] was modified with the data obtained in the present report. Macrolayer thickness in low heat fluxes for water and ethanol under atmospheric pressure was also measured by changing the orientation of the heating surface from a vertical direction to a downward direction. The data in low heat fluxes were thinner than the existing data measured by a probe method in the nucleate boiling region and agreed fairly well with the proposed correlation.

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Macrolayer thickness in transition boiling was determined from the energy balance relation q<tr>^^-=ρ_lH_fgδ_l·f, based on measurements of q<tr>^^- (time averaged heat flux in transition boiling) and f (detachment frequency of coalesced bubbles) for water and ethanol boiling on vertical and horizontal surfaces 15mm in diameter under atmospheric pressure. The macrolayer thickness for the vertical surface agreed well with the correlation proposed in the 7th report in this series, when heat flux at macrolayer formation is given on nucleate boiling curve extrapolated to the superheat of transition boiling. For the horizontal surface the macrolayer was apparently thick due to the in flow of bulkliquid beneath growing vapor masses.

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Heat transfer, vapor formation and pressure generation when a metal wire is heated very rapidly in water were investigated experimentally and theoretically for comprehensive understanding of highly transient, highly non-equilibrium thermofluid phenomena related to the physical process of vapor explosions. A small stainless steel or platinum wire, the diameter of which ranges from 0.lmm to 0.55mm, was electrically heated in water with a heating rate (wire temperature increasing rate) of l0⁶K/s to 10¹0K/s. Water temperature was changed from 20°C to 100°C to elucidate the effect of subcooling. Aspects of the phenomena were observed using high speed motion pictures with a frame speed of l00 000 fps to 20 000 000 fps. It was found that spontaneous vapor formation takes place, resulting in shock wave and high pressure when the wire surface temperature reaches the homogeneous nucleation temperature of water. It was also found that the maximum heat flux at the instant of spontaneous vapor formation is around several hundreds MW/m². A theoretical model is presented for the pressure generation, which is in good agreement with experiments.

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In this paper we propose a microlayer model in which the partial dryout of the liquid microlayer underneath the individual bubbles is regarded as the mechanism of critical heat flux (CHF). By considering the evaporation of the liquid microlayer and the dynamics of bubbles, both the initial growth and the departure process of bubbles are analyzed, then the dryout area and the heat flux are formulated as functions of superheat ΔT_s and the density of active sites N. Using the experimental data of N available in the literature, the CHF has been derived as the maximum value of the heat flux. The prediction of this model shows good agreement with some previous experimental data.

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The absorbers of absorption chillers consist of horizontal tube banks, over the outer surfaces of which absorbent flows and inside of which cooling water runs. The dependence of the distribution of absorption rate on the position of the pipes is important but has not been studied so far. In this work, the cases of one to three pipes are studied experimentally in the range of film Reynolds number between 5 and 40. Three different surfaces are tested to study the effect of wettability, Numerical calculations are also performed using the method proposed in our previous paper. The highest absorption rates are obtained for the pipes with higher knurls, and their distributions agree with the numerical predictions. The pipe position which shows the maximum absorption rate varies with flow rate but the maximum absorption rate does not vary greatly with flow rate. The heat transfer coefficient is minimum and almost constant with flow rate at the top pipe. At lower pipes it becomes larger, but tends to decrease with increasing flow rate.

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For understanding of fundamental chemical reactions under a highly nonequilibrium condition which is quite often used in plasma processing, the relevant atomic and molecular processes must be clarified. In this study, an analysis of the transition process to the excited state of an oxygen molecule induced by electron collisions in the oxygen plasma has been carried out. First, the electron density distribution in an oxygen molecule has been calculated using the extended Huckel molecular orbital method. Then, the electron potential energy distribution in the transition process to the excited state has been estimated. The electron behavior has been calculated using the estimated unidimensional electron potential energy distribution and unsteady quantum mechanics. As a result, the transition process to the excited state of an oxygen molecule induced by electron collisions and its conditions have been clarified qualitatively.

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An internal twisted tape, when used to initiate subcooled swirling flow boiling, is a very effective method of cooling components which are subject to high heat flux in a fusion reactor. In this study, the swirled channel was constructed using a copper cylinder (8mm inside diam., 190mm outside diam., and l00mm heating length), which was equipped with a twisted aluminum tape (approx. 0.5mm thick and 7.5mm wide), The values of the tape-twist ratio y (the length required to complete a single 180-degree twist of the tape divided by the inside tube diameter) were approximately l.8, 2.5, 3.2, 4.2, and infinity. CHF dependence on flow velocity and tape-twist was determined. Heating and cooling processes of large thermal capacity and inertia were used to obtain the wall heat flux via quasi-steady conditions, and several results for these limited cases are presented in the transition region near atmospheric pressure.

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Both heat and mass transfer in the gas phase and heat transfer in the liquid phase are examined experimentally for turbulent film condensation of organic binary mixtures flowing downward inside a vertical tube. For average heat flux, gas-liquid interface temperature and liquid phase Nusselt number, experimental results are compared with the analytical solutions based on stagnant film theory and heat transfer relationships for turbulent film condensation of pure vapors. The experimental results regarding heat transfer agree well with the analytical solutions, except that the liquid phase Nusselt number for ethanol and water mixtures is far higer in the experimental results than in the analytical solutions. This high liquid phase Nusselt number is considered to be caused by dropwise condensation in the liquid phase.

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Numerical investigation of flow and heat transfer around a single row circular cylinders was conducted using a boundary-fitted coordinate system, Numerical calculations for center-to-center distance between cylinders L/d=2.0, 2.5, 3.3, and ∞ were made of water flows in the Reynolds number range from 75 to 500. Numerical values of average Nuesselt number for uniformly heated cylinders are in relatively good agreement with those obtained from experiments in water (Prandtl number Pr &thkap; 8). The interference between wake flows behind cylinders, observed in the experiments, was also ascertained to occur with decreasing cylinder spacing L/d.

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The heat transfer coefficient of fluid flow was experimentally investigated in an annulus with an inner rotating cylinder to estimate thermal fatigue of the inner and outer cylinders on the rotating machine. The following three conclusions were reached in the study. (1) Within the range of experimental conditions, the heat transfer coefficient did not depend on the axial flow rate, rather it showed a large dependence on the inner cylinder rotating speed. (2) The heat transfer coefficient at the top of the labyrinth was about three times an large as that at the bottom. (3) An empirical correlation equation considering the gap between the inner and outer cylinders was proposed, which predicted the heat transfer coefficient on the rotating machine within ±30%.

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The characteristics of heat transfer and pressure distributions were measured by varying the clearances against the duct wall and the separations of the two thin plates for various arrangements of the thin plates which were oscillated by a flow in a parallel plate duct, with a view to enhancing the heat transfer along the duct. The maximum and mean Nusselt numbers have a Reynolds number dependence of Re^0.8, and were 2.3 and l.6 times those in the fully developed turbulent flow, respectively, for air with Reynolds number ranging from 9000 to 37500. A relatively new technique, i.e., full field infrared imaging, was used to obtain the time and spatial temperature profiles on the wall surface. Contours of the isotherm of the infrared images correspond well to the heat transfer characteristics and flow behavior.

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Numerical simulation was conducted on the heat transfer process in a two-dimensional flow field imposed by a sinusoidal oscillation of fluid. When gravitational force was ignored, the heat transfer at the wall was similar to a forced- flow turbulent heat transfer. On the other hand, under gravity, two modes of mixed convection heat transfer were observed depending on the thermal boundary conditions. For high-viscosity fluids, the bifurcation of the flow pattern appeared, which was mainly determined by the oscillation amplitude.

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A new type of heat exchanger with a stacked-sphere matrix is proposed. This heat exchanger comprises several segments separated by spacers. Each segment has a stacked copper sphere matrix formed by diffusion bonding. The ratio between the effective conductivity of the test heat exchanger matrix λ_e and the conductivity of copper λ_Cu was 0.09. Experiments were conducted to ivestigate the heat transfer in the proposed heat exchanger. The following results were obtained. (1) The overall heat transfer coefficient of the proposed heat exchanger is about 5 times as high as that without diffusion bonding. (2) The friction factor of the proposed heat exchanger is about 1.5 times as high as that without diffusion bonding. (3) Calculated overall heat transfer coefficients are almost the same as measured overall heat transfer coefficients. (4) The heat exchanger effectiveness is constant for λ_e/λ_Cu above 0.2.

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Heat transfer and defrosting characteristics of a horizontal single-row array of cooled tubes immersed in a gas-solid fluidized bed have been studied experimentally. The test fluidized bed with a low static bed height of l0mm produced excellent fluidization and effective gas-solid particle impinging jets for defrosting through the use of a newly developed cornice-type multislit distributor, in spite of very low pressure loss. The measured local heat-transfer coefficients and their transient behavior were discussed by consideration and comparison with these defrosting mechanisms. The defrosting limit when utilizing the present fluidized bed was also examined. It has been verified that frost-free running of the cooled tubes is possible with the use of this fluidized bed system under the conditions of inlet air temperature of -7°C, tube-surface temperature of -17°C, and relative humidity of 80%. Local contact frequency of particles onto the tube surface was measured by an optical sensing system and the defrosting mechanism of impinging solid particles was observed in detail by a visualization technique.

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The purpose of this study is to evaluate the correlation between the viability of milliscale biological materials and their effective thermal conductivity during extracellular freezing in order to achieve successful cryopreservation. The killifish embryo (Oryzias latipes, orange-red variety, φ1.3mm sphere) was employed as a sample biological material and the viability was evaluated by the hatching rate. Dimethylsulfoxide-water was selected as the cryoprotectant. The thermal conductivity was measured using a self-heated thermistor technique developed by T. A. Balasubramaniam (1977). The thermistor (φ2.5mm sphere) was installed at the bottom of a test section 8×8×12mm, and exposed to biological material. The cooling system was equipped with Peltier devices and was capable of reducing the temperature of the test section to -30°C. Between 150 and 200 embryos were loaded in the test section with 5, 15 and 20% w/w Dimethylsulfoxide-water. The effective thermal conductivity during extracellular freezing was measured over the temperature range -20 to 6°C with a cooling rate of 0.1 to 10°C/min. The effective thermal conductivity increased from 0.5 to 1W/ (m·K) with decreasing temperature and increasing the cooling rate. The decrease in the hatching rate and the variation in the effective thermal conductivity were correlated. Thus the viability could be controlled using their effective thermal conductivity during the extracellular freezing.

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Time-spatial measurements of cross-sectional mean liquid holdups along a tube axis were carried out in vertical upward huge wave flow and annular flow. In order to study the characteristics of liquid lumps such as liquid slugs, huge waves and disturbance waves, main wave-veins which were the traces of these liquid lumps on time-spatial liquid holdup maps were determined by an algorithm proposed in this paper. Distinctions between liquid slugs and huge waves were achieved based on the information about cross-sectional profiles obtained using a semi-supermultiple-point-electrode probes. Wave velocities and wave widths were determined by analyzing the wave-veins. Probability distributions of these flow parameters were also investigated. It is clarified that there exist distinct differences in wave velocities and wave widths between huge waves and disturbance waves at superficial gas velocities greater than l5m/s.

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Dynamic motion of displacers and basic performance characteristics at forced vibration of a free piston Vuilleumier heat pump (FPVM) were investigated experimentally and compared with 2nd order simulation results. One of a pair of one hot and one cold displacer was driven by a linear motor. Sensitivity studies were conducted with respect to key operational and environmental parameters such as driving frequency, hot gas temperature and motor input power. The dependences of phase angle and strokes of displacers on the basic performance of the Vuilleumier heat pump were also examined by driving both displacers of the FPVM prototype machine in order to investigate the performance characteristics of the FPVM operated at various phase angles and strokes. The dependence of the phase angle on the driving frequency of the hot displacer was opposite of the dependence on the driving frequency of the cold displacer. It was found that the simulation results agreed well qualitatively with the results of experiments.

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Experiments were performed to investigate the start-up and subsequent behavior of a water heat pipe with air-cooled fins for heat-source input steps from zero (frozen) to a constant level. First, the behavior of the water within the heat pipe was visualized, and measurements were made to obtain time-dependent wall-temperature profiles. It was found that the thermal resistance of the air-cooled fins is extremely small, the pipe causes dryout in the evaporator section, and wall temperature in that section rises rapidly. Second, measurements were made for different thermal resistance of the air cooled fins attached to the condenser section, different ambient temperatures, different heat inputs, and different charge rates of water. A correlation was obtained that can be used for successful start-up from the frozen state.

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Microscopic observations of the freezing process of onion skin cells have been made using a directional solidification stage, in order to study the freezing mechanism of living tissue. Experiments conducted under low cooling rates show that intracellular ice formation occurs due to surface-catalyzed nucleation (SCN) at the plasma membrane and proceeds cell by cell because the membrane blocks the growth of ice crystals. Since the probability of SCN increases with increase in the surface area in contact with the external ice, the tissue freezes at higher temperatures when the cell has a larger area in contact with the adjacent frozen cells. Dehydration and cell shrinkage were also observed in experiments with physiological saline simulating the effects of the vascular system in the organs. It is confirmed that a decrease of the cooling rate raises the dehydration rate and reduces the fraction of frozen cells but increases the amount of extracellular freezing.

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