Some factors are experimentally investigated concerning the method of cavitation inception measurement. They are definition of cavitation inception, effect of air content in tested water, effect of methods of pressure change in the cavitation tunnel and its rate of change. The test body is a circular cylinder in the range of flow of subcritical Reynolds number. In this flow condition, the cavitation bubbles occur in the separated shear layer behind the cylinder with large scatter of incipient cavitation numbers, according to past investigations. One of the most effective definitions is proposed for cavitation inception in the present work, where the main results are obtained using the proposed definition : (1) the inception values can be greatly reduced under water with small air content of less than a critical value, (2) the inception point can be affected by pressure change rate under the condition of variable flow velocity. At the same time, the measurement uncertainty on cavitation inception is also shown through a large number of measurements in the present experiment.

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In the present experiment, a single cavitation bubble is produced in a V-shape slot and the impulsive pressure is detected by four tiny pressure-sensor elements. The size of a sensor element is 1mm×1mm×2mm, and four elements are set every 1.7mm in a line on the top surface of the pressure sensor. From the experimental results, the following facts are revealed. Impulsive pressure caused by microjet impingement in the V-slot is several MPa which is almost the same as that near the plane wall. When the bubble is produced near the bottom of the V-slot, the maximum impulsive pressure is detected at a point 3.4mm from the microjet impingement point, which is a little further than the distance of 1.7mm on the plane wall.

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In order to find low-drag thin hydorfoils in cascades applicable to Kaplan turbines, we systematically investigate the subcavitating perfomance and the cavitation aspects around circular-shape hydrofoils for two cascade arrangements of various cavitation numbers and incidences. Our previous paper showed that the separation bubble near the leading edge, especially a long bubble, markedly increases the drag for thin hydrofoils in the cascade of present interest. Hence we investigate the behavior of the long bubble here. We try to suppress the long bubble, so that there is a marked increase in drag, by applying accelerating cascade effects of high-cambered hydrofoils effectively. We find a superior cascade hydorfoil, whose perfomance scarcely changes with cavitation number.

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Chaotic mixing in two-dimensional square cavity flows with a time-periodic lid velocity was numerically simulated. To quantify the mixing in the cavity, the pseudo-Lyapunov exponent λ was measured. We selected the Reynolds number (Re) and amplitude of lid velocity (A) as a parameter which governs the flow field and mixing conditions, and investigated the relationship between these parameters and λ. The obtained results showed that neither Re nor A affects the value of period T which gives the maximum λ.

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To elucidate the effect of tube diameter on the vertical upward gas-liquid two-phase flow in capillary tubes, characteristics of velocity and flow behavior of liquid lumps (namely, liquid slug, huge wave and disturbance wave) are investigated experimentally. The tube diameters were changed from the maximum value of 26.0mm to the minimum value of 0.5mm. In the flow regimes of the huge wave and disturbance wave, the effect of tube diameter on the velocity of liquid lumps is distinctly recognized. When the diameter decreases from 26.0mm, the velocity of liquid lumps gradually increases, but it drastically decreases when the diameter is less than 2.0mm.

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Measurements of time-mean velocity, longitudinal, normal and lateral velocity fluctuation intensities (u', v', w') and of wall shear stress have been made in turbulent flows in a flat channel and in boundary layers (zero pressure gradient). The profiles of u', v', w follow a similar pattern, to a reasonable approximation. The wall shear stresses obtained by different techniques have been compared. The same equipment was employed in boundary-layer measurements, and the results are compared with those obtained in channel flows. Comparisons of fluctuation intensities, and two constants A and B in the universal law of the wall, where A is the slop constant and B is the 'slip' within the viscous layer interposed between the smooth wall and the fully turbulent flow, have been made with values obtained by earlier investigators for both channel and boundary-layer flows.

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Experimental study was carried out to examine the effects of pressure gradient alternating in sign for the turbulent channel flow. Air flow was decelerated through a linearly diverging section, and then accelerated through a linearly converging section. Experiments were performed with two different channels. The velocity profiles in the wall region were displaced above the universal law of the wall, and Karman constant x increases in the converging section. Turbulence intensity and Reynolds shear stress in the converging section were considerably lower than those in the diverging section. The behavior of the increase or decrease of heat transfer coefficient was similar to that of Reynolds shear stress.

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The Reynolds number effect on the turbulent structure of a d-type rough wall turbulent boundary layer was studid experimentally in terms of the coherent structure. Mean bursting frequency, conditional averaged velocity signals and fractional contribution of the stress-generating motions were obtained with both the VITA method and the four-quadrant analysis, respectively. The effect of the three parameters, namely, bulk Reynolds number R_θ, roughness Reynolds number and friction parameter u_τ/U₁, were considered in the present study. Even scaled with the inner, outer and mixed variables, the nondimensional bursting frequency depends on the Reynolds number. The relative magnitude of fractional stress contribution of ejection to that of sweep increases with decreasing Reynolds number.

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Detailed studies are conducted to investigate the effects of the incident wakes generated by rotating circular cylinders on the characteristics of the transitional boundary layer on the flat plate. In this report, the primary focus is set on the measurement of the time-averaged heat transfer distribution along the flat plate under several conditions of the wake characteristics and the cylinder rotating speed in order to develop simple models in terms of intermittency for the prediction of the transitional behavior of the boundary layer subjected to wakes. Two transition models are employed to be compared with the measured heat transfer data, and then it is found that the geometrical intermittency model which only considers evolution of the turbulent spot in the space-time domain yields better prediction as a whole.

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Shock wave propagation over a perforated wall and wall discharge coefficient through the perforation were studied experimentally and numerically. The experiment was conducted in a shock tube equipped with double-exposure holographic interferometry. Shock Mach number was 1.54 in air and the wall perforation ratio was 0.4. The numerical simulation was conducted by an upwind finite difference scheme using the TVD scheme. To determine the wall discharge coefficient through the perforation, the numerical result was compared with the experimental one. The wall discharge coefficient through the perforation was obtained as 0.54, and this value can be extended to the perforation ratio ranging from 0.1 to 0.5, a shock wave Mach number of 1.5 to 5.5 and a corresponding Reynolds number of 1.24×10⁵ to 9.78×10⁵.

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The structure and behavior of a vortex ring and secondary shock waves which were generated behind the shock wave discharged from the open end of a square cross section shock tube were investigated experimentally and numerically. Double exposure diffuse holographic interferometry was used to observe this complicated three dimensional shock wave phenomenon. This diffuse holographic interferometric visualization is particularly useful to understand three dimensional flow. The TVD finite difference numerical simulation was carried out by solving the three dimensional unsteady Euler equations. A comparison was made between experimental results and computational results. These results clarified the generation and the transformation of the vortex ring and the behavior of three dimensional secondary shock waves.

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The purpose of the present study is to clarify the Rankine-Hugoniot relations for Lennard-Jones liquids. First, Monte Carlo simulations are conducted to evaluate the pressures, the internal energies, and the sound velocities. These computed values are used to obtain the approximate expressions by the method of least squares. The Rankine-Hugoniot relations are then clarified numerically as a function of the shock Mach number by solving the basic equations together with those approximate expressions. For the liquid shock waves, not only the pressure but also the temperature increases much more than those for ideal gases. The results obtained here enable us to conduct more effective molecular dynamics simulations, such as simulations of the shock fronts alone, for the study of internal structures of liquid shock waves.

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In this paper, the influence of various factors on satellite formation and the behavior of satellites are experimentally examined in a uniform satellite region in which satellites are released very regularly from the tip of a nozzle under nonuniform magnetic fields. For that purpose, the outside diameter of the nozzle (the inside diameter is constant) and the inside diameter of the nozzle (the outside diameter is constant) are widely varied. In addition, liquids having different values of density and surface tension are used. Then, various factors governing the appearance condition of the satellite and the satellite diameter are found by dimensional analysis. Furthermore, empirical formulae for dimensionless magnetic force per unit volume and dimensionless satellite diameter are given.

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The dynamic behavior of a magnetic liquid drop on a non-magnetic solid base subject to magnetic fields and vertical vibration have been studied experimentally and theoretically. The frequency responses of a single magnetic liquid droplet are investigated. Measurements have been made of the amplitude of time-varying height and the contact angle of a magnetic droplet on a horizontal solid base. It was found that the magnetic liquid droplet responds to the excitation in the elongation and contraction of its height. The frequency of the time-varying droplet height and contact angle corresponded to the excitation frequency. Theoretical analysis explains the experimental results of the droplet motion, that is, the droplet height is determined by the Bond number, the magnetic Bond number and the vibration Bond number.

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In this investigation, the authors have studied the stability of steady flows in collapsible tubes, which were theoretically calculated in the previous paper. The dynamics of the collapsible tube is approximately represented by a simplified lumped parameter model. On the basis of the model, the instability condition has been derived and the mechanism of the instability of the steady flow has been clarified. The instability region obtained theoretically is qualitatively in good agreement with the experimental results.

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Flows around a rotating square cylinder in a uniform crossflow are studied numerically. The body-fitted grid generation on moving boundaries is used to obtain the numerical solution of the incompressible Navier-Stokes equations. The time-dependent curvilinear coordinate system which coincides with a contour of a moving boundary is transformed into a fixed rectangular coordinate system in a calculational plane. The results of this method are compared with previous experiments, and the confidence is confirmed. The changes in the stream lines, pressure distributions, C_D and C_L as the cylinder rotates are obtained.

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A new analytical approach to optimize shapes of the flow field is presented. The reshaping is accomplished by the growth-strain method which was developed as a method using finite-element calculation of the deformation of shapes by generating bulk strain of swelling and contracting to the solid problems first. The generation law of the bulk strain is given as a function of a distributed parameter to be uniformized. To the solid problems, the validity of the use of the shear strain energy density to maximize the strength based on the Mises criterion or the strain energy density to maximize the stiffness for the distributed parameter has been confirmed. In the present paper, we propose to use the dissipation energy density for the distributed parameter to minimize the total dissipation energy by viscosity to the fluid problem. Numerical results for abrupt enlargement channel problems in steady state assuming low-Reynolds-number and noncompressible viscous fluid show the validity of the present approach.

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The Q-branch multiplex CARS method has been applied to simultaneous measurement of the distributions of the rotational temperature and number density in pure nitrogen plasma jets. Temperature and number density are measured by comparing an experimental CARS spectrum with a theoretical one. The plasma jets are produced by DC discharge (150A, 14-16V) and expanded to an evacuated chamber. Because of relatively low ionization, the signal of CARS is strong enough to measure temperature and number density of molecules in the electronic ground state. For backpressure of less than 20 Torr, shock waves of jets are observed, which correspond to the distribution of measured temperature and number density along the centerline of jets. However, for backpressure of more, than 50 Torr, the flow becomes subsonic and the shock waves disappear. The effect of the pressure deviation and the fraction of excited nitrogen to the theoretical spectrum are investigated through evaluation of the error of temperatre and number density.

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In this study pressure pulsation in a discharge flow system of a rotary compressor for air conditioning use is analyzed theoretically by transfer matrix method by using a model of piping system which consists of three volumes (a valve chamber, lower and upper chambers in a hermetic casing) and three pipes (a cylinder path, a motor path and a discharge pipe). Theoretical calculation indicates that intermittent discharge flow from a cylinder causes certain pulsations in both lower and upper chambers in the casing, and the calculated results are in good correlation with measured ones in phase and amplitude of the pulsation. It is also confirmed theoretically and experimentally that a pressure differential force acting on a motor rotor due to the pulsations in the lower and upper chambers induces a longitudinal vibration of the rotor.

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The effects of scroll divergence angles on the performance characteristics of a multiple-disk laminar flow fan and the flow condition around an impeller are experimentally investigated. The discharge angle of the fluid leaving the impeller is very tangential and the velocity is very large at the higher impeller efficiency point. The use of a large divergence angle scroll, for the conversion of the angular momentum in this flow to the high-pressure head, causes large pressure loss due to deceleration when the fluid leaving the impeller flows into the scroll casing. Moreover, in the case of the large divergence angle scroll, the flow conditions around the impeller are very nonuniform. On the other hand, in the case of the small divergence angle scroll, the flow conditions around the impeller are very uniform and the fan efficiency increases, but the pressure loss due to the scroll wall friction is very large at the large flow rate operating range.

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In order to establish a performance prediction method of mixed-flow pumps in all flow ranges, the inlet and outlet flow characteristics are measured and the characteristics of inlet reverse flow in low flow range are discussed, as it exerts remarkable influence on the performance. The reverse flow characteristics at the impeller inlet are determined experimentally, and their influence on the theoretical head is discussed.

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In louvre-blind-type cryopumps of rectangular cross section with opening distance B, width C and depth D of the cryopump, the influence of shape, size and location of louvres on the transmission probability is calculated by Monte Carlo simulation. The following results are obtained. (1) The transmission probability of cryopumps designed with dimensional ratios of B/C=0.59∼0.86 decreases rapidly for D/B ratios less than 1.2. (2) Most gas molecules flowing out of the cryopump after reflecting at the louvres reflect at the louvres for D/B ratios less than 0.6.

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This is the first report on our attempt to establish a theoretical model predicting the full boiling curve from nucleate to film boiling region. In the model presented here, the boiling curve is calculated based on a theoretically calculated fraction of liquid-solid contact and correlating equations for nucleate and film boiling heat transfer. The model determining the fraction of liquid-solid contact is developed based on the following three mechanisms, which have been proposed for the transient CHF : macrolayer dryout, packing of bubbles created by boiling nucleation, and packing of bubbles by spontaneous nucleation. The calculated results show that the present model can describe the outlines of full boiling curves and quantities for liquid-solid contact.

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The aim of this study is to clarify the fundamental features of the flashing phenomenon of cryogenic liquid nitrogen under rapid depressurization. Liquid nitrogen flashing experiments have been carried out using a cryostat with windows. From these experimental results, it is shown that a pressure recovery process after rapid depressurization occurs when bubbles generated in the lowtemperature region grow and rise in liquid nitrogen. Furthermore, local minimum pressure and pressure recovery within the vessel are predicted by saturated pressure corresponding to initial liquid temperature. The local minimum pressure depends strongly on initial temperature rather than on the rate of depressurization.

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The primary purpose of this study is to investigate the pressure effects on liquid and gas slugs in the plug flow regime. In this study the pressure in the closed-loop system was changed from 0.3 to 20MPa at a constant fluid temperature on horizontal flow. The point of disappearance of the liquid slug, mean lengths of gas and liquid slugs, and the frequency distributions of gas and liquid slug lengths were measured to investigate the characteristics of plug flow. The approximate experimental equation for the mean length of the gas slug and the point of disappearance of the liquid slug is presented.

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Solid/liquid phase-change heat transfer in porous media has been extensively studied in the past several years, and effects of various parameters on the heat transfer have been clarified. In such systems, the heat transfer coefficient is usually very small due to a small thermal conductivity in the systems and a large resistance to the fluid flow due to a porous matrix. Therefore, some means for heat transfer enhancement is needed for the systems. The use of conducting plates (or fins) may be considered quite reliable and effective for this purpose. As far as the authors could determine, no numerical studies appear to have been reported on the melting process around a hot surface with the conducting plates. In the present study, numerical calculations have been performed using an enthalpy method for melting processes around a hot wall with/without conducting plates. These results have been compared with experimental ones.

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Under mechanical deformation in the solid state or shear stress in the molten state, molecular orientation takes place in polymer materials. This orientation of long chain molecules causes the anisotropy of not only mechanical strength but also of thermophysical properties. Although the anisotropic behavior of thermophysical properties is important information needed for advanced applications of polymer materials, no reliable methods for determining direction dependence of, for example, the thermal diffusivity are available. In the present study, anisotropic behavior of thermal diffusivity was experimentally studied in PMMA samples shaped in a spiral testing mold by an injection molding machine. The method used was the forced Rayleigh scattering method, a newly developed optical method. The influences of such factors as temperature of the melt, solidification process and the backpressure were quantitatively measured, and the relations among shear stress, molecular orientation and thermal anisotropy were discussed.

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Heat transfer experiments were carried out for a turbulent channel flow with fluid injection through one channel wall. An infrared-radiation thermometer was used for the measurement of wall temperature. Special attention was paid to the region close to the starting point of injection, where laminarization of the flow was observed in previous studies. Measurements were made at seven streamwise positions and the channel Reynolds number changed in four steps for various injection rates. It is demonstrated that all the obtained results can be correlated well if the reduction rate of Stanton number, St/St₀, is plotted against the injection parameter B_h. The developed correlation is found to be close to the relationship established for a flat plate turbulent boundary layer. This suggests that neither the pressure gradient necessary for internal flow nor the flow laminarization seriously affect the reduction rate of the heat transfer coefficient due to fluid injection.

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The effects of free stream turbulence on the Reynolds stress and the turbulent heat flux in the turbulent boundary layer on a flat plate are studied experimentally. The measured turbulent quantities in the turbulent boundary layer are classified into four quadrants. From these measurements, the following results are obtained. As to the temperature field, the contributions of the sweep-type motion are greater than those of the ejection-type motion for the near-wall region with increasing free stream turbulence, and as to the flow field, the contributions of both types of motions are larger than they are in the case of no turbulence grid. The measured enhancement rates of the heat transfer coefficient and the wall friction coefficient are determined from the intensity of free stream turbulence and from the integrated turbulent length scales in the free stream.

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The behavior of a thermally stratified mixing layer formed in a circular pipe has been experimentally investigated in order to estimate the thermal stress of the horizontal pipe wall caused by the emergency cooling of power plants. Two component velocities and the temperature of fluid are simultaneously measured by fiber LDVs and a hot film thermometer. Experiments were performed at the bulk Reynolds number of 7350 where the overall Richardson numbers ranging up to 2.46. Flow visualization at the cross section of the pipe and measurements of the turbulence characteristics in the fields of velocity and temperature showed the difference of flow structure between isothermal and thermally stratified conditions. Upper and lower layers mixed well in the isothermal condition, while in the thermally stratified conditions, there obviously existed a thermally stratified mixing layer where turbulent mixing was suppressed by the buoyancy effect. This thermally stratified mixing layer spread in the horizontal direction with increasing Ri number and generated secondary flow between the wall and this mixing layer.

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The combustion characteristics of hydrogen jet diffusion flames on a flat plate in a cross flow were experimentally studied. It was found that stability limits and shapes of the flame were affected strongly by the air stream velocity U_e of the cross flow. In this experiment, when U_e was slower than 9.5m/s, there existed critical injection velocities of hydrogen U_j at which a hole appeared on the front side of the flame at the transition point from laminer to turbulent. As the hydrogen injection velocity U_j was increased further, the hole became larger and finally the flame was lifted, not to blowout. When U_e was increased more than 9.5m/s, flames with a hole were formed as soon as hydrogen was injected. When U_e was increased more than 16m/s, the flame occurred to blowout. No flame stabilized at the air stream velocities over than 21m/s. The effect of U_e and U_j on the flame shapes was also investigated. It was cleared that the momentum ratio of the air stream to the hydrogen jet was the most important parameter determining the flame shapes.

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Vegetable oils appear to be one of the alternative fuels for supplementing diesel fuel in the future. Considering the CO₂ problem, alternative fuels from regenerated vegetable energy sources have many advantages. Furthermore, vegetable oils are suitable for use in agricultural machine engines with respect to the user's capability of self-support. In studies of vegetable oils, the mixtures of gas oil or ethanol with vegetable oils and vegetable oil methyl esters on engine performance and exhaust emissions have been reported. This paper describes experiments with stable water-emulsified rapeseed oils in a small direct-injection diesel engine for utilization as a diesel fuel. The results show that the NO_x concentration decreases remarkably with increasing water content. However, an optimum water content exists with respect to engine performance and exhaust smoke concentration.

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The sooting process during combustion is described by a theory based on cluster kinetics. The likelihood of soot formation via soot clusters at higher temperatures is suggested from the fully kinetic calculations in which carbon vapors (C₁-C₅) and polyacetylenes are assumed to be as the colliding partners for cluster reactions. The predicted results of the proposed theory well explain both the bell shaped temperature dependence of soot yields and the rapid soot formation as known from shock-tube experiments. It is shown that the small clusters are mainly generated via C₂H and they grow into large clusters on the reaction with carbon vapors at moderately high temperatures while they are decomposed into carbon vapors at extremely high temperatures. Furthermore, the effects of pressure and temperature history on soot formation are discussed.

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This paper presents a systematic study regarding the durability of exhaust valve of diesel engines burning heavy fuel oil. This study has been conducted with the aim of clarifying the mechanism of blow-by in order to estimate the temperature of exhaust valve seat in operating engines. It is necessary to treat the relationship between the corrosion of the exhaust valve seats in onboard operating conditions and surface temperature of the valve seats. It has been confirmed that although the temperature of the normal exhaust valve seats is low for hot corrosion during engine operation, the seating surface temperature in the onboard operating conditions exceeds the critical temperature for hot corrosion by taking into consideration the temperature rise caused by the high temperature and high-pressure combustion gas blowing at a high velocity through local gaps of the valve seats.

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The behavior of the longitudinal vortices shedding from a cruciform arrangement of two circular cylinders with an equal diameter d is investigated using a wind tunnel. The longitudinal vortices shed periodically near the crossing corner of the cylinders when the gap s between them is less than d/2. The nondimensional shedding frequency, S_tM, of the longitudinal vortices is independent of the Reynolds number Re when 730<Re<34, 400. The value of S_tM is : 0.06<S_tM<0.09 when s/d<0.25 and S_tM&cong;0.04 when 0.25<s/d<0.5. The fluctuating lift force on the upstream cylinder caused by the longitudinal vortices is estimated from the pressure measured on the cylinder surface. The result correlates well with values obtained from the oscillation amplitude of an elastically supported upstream cylinder. Effects of the oscillation of the upstream cylinder on the longitudinal vortex shedding are also investigated, and a phenomenon similar to the "lock-in" of the Karman vortex shedding is found in certain ranges of s/d and the free-flow velocity.

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The authors made an analytical model of the heterogeneous and homogeneous solid-liquid two-phase flows between two parallel plates, and investigated the velocity and concentration profiles estimated by numerical analysis of this model. We tried to avoid the use of too many experimental constants or coefficients of an arbitrary nature, and made the analytical model with well-known equations as much as possible. However, mutual interaction of particles and interaction between particles and walls are not considered in this model. After the comparison between estimated and experimental values, we obtained the following conclusions: the estimated velocity and concentration profiles almost agree with experimental ones, and these profiles agree well within a tenfold distance of between two flat plates under the same Fr number.

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Investigations for air flow turbulences are quite important to clarify small-particle contamination mechanisms in clean chambers. Strongly fluctuated air flow turbulence is recognized behind pleated air filters. Turbulent flow characteristics behind pleated high-efficiency particulated air filters are numerically analyzed and studied by direct simulation using a 3rd-order Kawamura-Kuwahara scheme. As the result of the study, the following typical phenomena were found: (1) Free shear caused by flow velocity nonuniformity makes vortex streets behind the filter ends. These vortex streets interfare with neighboring streets and spanwise synchronized fluctuation is generated. (2) Streamwise distribution of <u'²> has a sharp peak with some distance from the filter ends. This peak appears at the position the vortex interference starts. Rate of the mean velocity change becomes maximum in this position. (3) Results calculated by direct simulation are qualitatively in good agreement with the experimental results.

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The motion of capsules was numerically analyzed by the method of characteristics. It was determined that the velocity of a capsule with large mass is lower than that with small mass, and that a collision occurred when capsules of different masses are loaded into the pipe line with a lower inlet pressure head. Time histories of pressure are also examined near the capsule loader and near the outlet of the pine line. To confirm the numerical analysis, we carried out measurements in a horizontal pipe line using capsules of different masses with wheels. The numerical solution shows good agreement with the measurements.

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An experimental study is carried out for a swirling flow pneumatic conveying system in a horizontal pipeline in terms of the pressure drop and solid flow patterns. The test section consists of a pipeline 13m in length with an inside diameter of 80mm. The three inital swirl numbers in the range of 0.58 to 1.12, the average gas velocity from 10m/s to 23m/s and the solid-gas ratios ranging from 3.5 to 14 were investigated. Polyethylene pellets of 3.1mm were used as the solids conveyed. It is found that in the lower gas velocity range, the pressure drop and the gas velocity at the pressure drop minimum for swirling flow pneumatic conveying were lower than those for axial flow pneumatic conveying. The fluctuation of wall static pressure of swirling flow pneumatic conveying decreases compared with axial flow pneumatic conveying.

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The rotors and stators of turbomachinery operate in various types of shear flows such as boundary layers, jets and wakes, and further operate in supercavitating condition in the case of high speed hydraulic machinery. This paper aimes firstly to develop a linearized theory for the two-dimensional supercavitating hydrofoil in exponential shear flow and secondly to clarify the effects of shear parameter on both cavitation and force characteristics of hydrofoil in that shear flow.

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An experimental investigation was made into the effects of four design parameters such as, (1) the number of disks, (2) the rotational frequency, (3) the thickness of disk, (4) the gap between two disks, on both noise and fluid dynamic characteristics. As a result, it is made cleared that the sound power is nearly proportional to the number of disks and the sixth power of the rotational frequency. The thickness of the disk and the gap between disks hardly affect the fan noise and relative velocity. The specific noise level of the laminar flow fan is comparable to that of the centrifugal fan. The noise generated from the laminar flow fan is almost controlled by turbulent noise.

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The two-phase boundary layer equations for free-convection condensation of an air-steam mixure on a vertical flat surface are numerically solved in the bulk air concentration range from 0.18 to 0.98 at 100 kPa. From the results, two correlation equations for convection heat transfer from the bulk to the vapor-liquid interface are obtained; the one contains the effect of the enthalpy diffusion term in the energy equation, and the other is derived from the saturation temperature gradient corresponding to the mass concentration gradient at the vapor-liquid interface. By using these equations, two algebraic equation systems for evaluating the heat flux at the cooling surface and the condensation mass flux are derived. A comparison between the solutions of the algebraic equations and Fujii and Kato's experimental results yields the following conclusions: (1) the theory agrees with the experiment within an error of 10% for the condensation mass flux, and (2) in the case of large bulk air concentration, the heat flux at the cooling surface which is calculated by using the saturation temperature gradient for convection heat flux in the vapor phase agrees well with the experimental results.

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In the previous study, top flooding in thin rectangular channels could be characterized by using the wider span W as a characteristic length in the Wallis nondimensional velocity. To further study the flooding characteristics related to the span W, top flooding experiments in thin rectangular channels of different span W were conducted. When the liquid penetration into the channels was small, the span W was the most inportant characteristic length. However, when the liquid penetration was large, the span W was not an appropriate scale. The nonuniform distributions of void fraction and velocity in the spanwise direction can be represented by the span W at the low liquid penetration region. But in the high liquid penetration region, random penetration of liquid along the spanwise direction mitigated the role of W.

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Heat transfer in a plate-type reformer tube has been clarified by both experimental data and one-dimensional analysis. Reaction heat was approximately 80% of gross heat absorption, and the overall heat transfer coefficient in the packed bed was 5 times as large as that of nonchemical reaction. The major reaction was performed at the upper portion of the tube along the plate fin heat exchanger. Heat flux distribution was focussed by the porous medium, but its contribution to the reaction was not so remarkable. The reaction heat went partially beyond absorbed heat, and gas temperature decreased slightly with sensible heat consumption. It was found that the process gas inlet temperature was the key parameter in reforming reaction enhancement.

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In order to establish an effective and accurate numerical method available for internal flows with transpiration in which large computational domain and local fine allocation of grid points are required, a finite-difference scheme based on a multigrid method combined with the quadratic upwind interpolation for convective kinematics (QUICK) was tested. SIMPLE was used as a smoother, and an alternating direction implicit (ADI) method was adopted to secure rapid and isotropic propagation of a change in a variable occurring at one grid point to its surroundings. Additionally, velocity correction was made so that the correct mass flow rate of fluid was secured at every streamwise grid point. Some detailed discussion is given to the obtained results, and the effectiveness of the present method is demonstrated.

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An unsteady single spray of n-decane which was miscible with a small quantity of exciplex-forming dopants was impinged on a flat wall with high temperature at a normal angle in a quiescent atmosphere in the experiment presented here. It was possible to generate fluorescent emissions from vapor and liquid phase in this evaporating and impinging spray, when a thin sheet of laser light from Nd : YAG laser was passing through the cross section containing the central axis of this spray. Then, clear 2-D images of vapor and liquid in the spray were acquired by this method distance between the outlet of the injection nozzle and the wall.

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In the case of compressible viscose fluid flow in a duct, the velocity, density and other physical parameters on each cross section are never uniform. Upon analyzing such non uniform flow, however, it is very convenient in practical use if it can be treated as an one-dimensional flow without decreasing the accuracy of the analysis. For this reason, the optimum mean value in a compressible real fluid flow in a duct, is discussed in this paper. By using the arailable present mean values which are based on mass flux, the well-known one-dimensional basic relations of gas dynamics are consistently generalized into the actual flows by simpler relations. The characteristics of the correction factors, which arise in the present treatment, are clarified for Reynolds number and Mach number. The apparent error occuring in the uniform flow analysis can be successfully estimated by the present method.

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