In numurical fluid analysis, high accuracy and upwinding are necessary for the convection term of the Navier-stokes equation because this term is non-linear. In general, bilinear element is used in FEM (Finite Element Method) and the discretization by this method corresponds to the 2nd-order central difference. As a result, we can't obtain adequate accuracy for high Reynolds number flow. Although many upwind methods have been proposed, we use CIP (Cubic Interpolated Pseudo-particle)-FEM in the present work, and analyze natural convection in a cubic cavity. This problem has been analyzed by many investigators. However, it is difficulut to analyze this flow at high Rayleigh numbers Ra≥10⁷ because numerical divergences and vibrations occur in the energy equation. We analyze natural convection at 10³≤Ra≤10⁸ and show that the present scheme analyze this flow stably and is effective by comparing with other numerical results.

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Nowadays, it becomes more and more important to calculate magneto-hydrodynamics (MHD) flows under AC (Alternating current) magnetic fields, in order to control the molten metal processing in the furnace by the electromagnetic force. In this paper, three dimensional problems for the arbitrary shape model are solved by using the hybrid FEM-BEM (hybrid finite element method-boundary element method) with the A-〓 (magnetic vector potential-electric scalar potential) method in the electromagnetic field and using the ALE-FEM (arbitrary Lagrangian Eulerian-finite element method) in the velocity field with free surface. The strong point of the ALE method is that the element itself is moved along the velocity of the fluid, and consequently, the boundary between fluid and the air is shown precisely. Using these distinct methods in each field, we can observe the complicatedly tangled physical parameters of the electromagnetic field in the cold crucible and confirm the unique shape and vibration of the surface.

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Interaction between the vortice shed from the blades of helicopter-rotor and the blades themselves is studied numerically by the three-dimensional vortex method as a basic study of the so-called blade-vortex interaction (BVI) noise. The blades surface is represented by source panels and the stick method is used for calculating the motion of the free vortices. Two types of tip shapes, rectangular and tapered blades, of the rotors are compared. Pressure fluctuation, which will be related to the BVI noise, is obtained, and it is shown that circulation of the shed vortices from the tip of the tapered blades is smaller than that of the other and also that the pressure fluctuation is also smaller.

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Evolution and interaction processes of the three mean vorticity components were investigated experimentally by evaluating production terms in the vorticity transport equations. The measurement was made in a stronger wall jet managed by two kinds of streamwise vortex pair, namely, common-flow up and common-flow down. It is discussed that contribution of the production terms on the evolution of the mean vorticity and differences in the results between the two kinds of vortex pair. The production term expressed by product of mean vorticity and velocity gradient can be understood as the reorientation between the spanwise and vertical vorticity components under existence of the streamwise vorticity. The reorientation mechanism produces negative mean velocity gradient ∂U/∂y intensifying the large-scale eddies in the outer layer of stronger wall jet. Magnitude of the produced negative mean velocity gradient ∂U/∂y is larger in common-flow up case in which the streamwise vortex holds relatively round shape, that is, smaller ratio of spanwise radius and vertical one.

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Flow instability in a vaned diffuser with even number of blades was examined experimentally and analytically. In experiments, alternate blade stall, asymmetric stall, and two types of rotating stall (backward/forward) were observed depending on the impeller/diffuser clearance. For narrow clearance with strong impeller/diffuser interaction, the alternate blade stall and backward rotating stall mainly occurred. As increasing the clearance, the forward rotating stall also occurred, and the onset shifted toward the high flow rate corresponding to the pressure performance in the vaned diffuser. Simple 2D stability analysis showed that the clearance between the impeller and diffuser affects the speed and direction of stall propagation, and the gradient of the pressure performance in the vaned diffuser affects the onset of the rotating stall.

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The Effect of non-uniformities of inlet velocity profile on performance of annular diffusers was investigated by numerical simulation. The numerical results indicate that the pressure recovery factor strongly depends on the maximum exit velocity, and the pressure recovery factor of diffusers decreases as the non-uniformity of inlet velocity profile becomes larger. In the case of the larger velocity on the shroud wall, there is the effect of the wall angle on the diffuser performance. And the pressure recovery factor of the diffuser with a diverging hub is higher than the other with a converging hub. It was clarified that it is necessary the optimal combination between the inlet velocity distribution and the wall angle of the duffuser to design a high performance annular diffuser.

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As one of the important aerodynamic problems of magnetic disk drives for microcomputers, a flow between shrouded corotating disks and its instability have been investigated. The four-decker circular disk pack is enclosed in a cylindrical container to endure the axial symmetry. Mean and fluctuating velocity fields induced by the disk rotation has been obtained by employing fine scale multi-sensor hot-wire probes. First, the velocity distributions of 2D axisymmetric base flow field are reported. The occurrence of 3D non-axisymmetric flow will then be discussed, where the rotational speed as well as the number of cells will be discussed and compared with the existing data.

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Flow past a circular cylinder with a highly water-repellent wall has been investigated using a flow visualization technique at Re=50. Test cylinder is 20 mm in diameter. The basic material of the highly water-repellent coating is fluorine alkane modified acrylic resin with added hydrophobic silica, which was left overnight in air after it was coated to the cylinder wall. The flow patterns agreed with that of the analytical results obtained by applying the fluid slip boundary condition. The maximum value of the drag reduction ratio was about 25% for the highly water-repellent wall cylinder at Re=50.

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Uniformly making a liquid film on a rotating substrate is of great practical importance. However, despite its frequent use in practical processes, the liquid film on a large-size substrate has never been examined. We have thus visualized the flow patterns of a liquid film on a large-size substrate (650mm×830mm). There are two kinds of flow patterns on the liquid film : a turbulent-transition flow pattern or a striped flow pattern. We measured the effects of the change of kinematic viscosity of the liquid, the flow rate of the nozzle, and the angular velocity of the substrate on the striped flow pattern. Moreover, we devised a new equation to predict the onset point of the striped flow pattern. And it was found that the predicted onset point agrees well with the measured one.

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Estimation of turbulent noise level with L-weighting and A-weighting functions was proposed to a centrifugal fan without scroll casing. The validity of these formulae was examined experimentally in respect to the effects of parameters ; inlet/outlet area ratio of impeller and five fan types. The agreement between the measured and the predicted values of the width of wake and the mean relative velocity was satisfactory. Moreover the experimental values of the overall turbulent noise with L-weighting and A-weighting functions agreed well with the predicted values. Finally, the effects of slip factor and the inlet/outlet area ratio of the impeller on the relative velocity, the width of wake, the sound pressure level and the specific noise level are shown.

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Model simulations to show autonomous property of near-wall layer below lower edge of logarithmic layer are conducted for a channel flow. A model to remove interaction between two layers top and below of a plane parallel to the wall, by assuming zero wall-normal velocity on it is employed for this purpose. It turned out that near-wall layer needs a definite minimum thickness to maintain turbulent regime if no interaction with upper layer is allowed and that the layer has universal turbulent structure if turbulent regime is allowed irrespective of any interaction with above layer. The universality holds for any wall condition such as to lower wall friction, with different structure depending on each wall condition. Simulations to trace time evolution of a small pair of quasi-streamwise vortices submerged in a laminar flow of mean turbulent velocity distribution were also conducted to see the basic structure of the universal near-wall turbulence. The energy budged of the grown-up structure which is composed of a couple of hairpin vortices and subsidiarily generated quasi-streamwise vortices is similar to that observed in natural turbulent channel flow.

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An optimum condition for suppression of separation was investigated experimentally. A two-dimensional airfoil of NACA 0015 with a large angle of attack was used to generate a separation. The flow near the surface was sucked in by four suction-cells independently. The cells were arranged in line at the center of the span. Several combinations of active cells and their suction volumes were tested to obtain the minimum power consumption of suction required for the suppression of separation. The extent of suppression was judged by the velocity profile obtained by flow visualization near the trailing edge. Each cell showed an optimum value of the suction volume for a specific angle of attack with separation. It was found that the suction performance of a cell was greatest if the cell was placed just in front of the separation point. A large saving in suction power was achieved when the cells were placed just in front of and at the separation point.

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This study is concemed with the turbulent structure of a radial jet which is deflected by the impingement with an annular jet. Probability density functions, turbulent energy spectra, auto-correlations, and two-point correlations of the streamwise fluctuating velocity are measured and the differences of the turbulent structure between a radial free jet and a deflected jet are clarified. The fluctuating velocity field of the deflected jet in the region near the nozzle exit becomes relatively methodical in comparison with a free jet and the large-scale structure dominates in place of the small-scale structure of a free jet which suggests an organized eddy structure.

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In a centrifugal blower with diffuser vanes, the noise level may unexpectedly increase at certain numbers of revolutions. In particular, the phenomenon of acoustic resonance due to aerodynamic interaction tones between the impeller and the diffuser is a serious problem. In this paper, we develop a physical model to describe this phenomenon. The model assumes that inner flow paths both in the impeller and the diffuser behave as quasi-one-dimensional acoustic tubes. We constructed a mathematical model to predict critical numbers of revolutions at which resonance occurs, and conducted experiments to verify the model, and the results agree well with the mathematical model. We also propose an effective method for suppressing the resonance in which diffuser vanes with slits are used. Each diffuser vane has a slit located just behind the end of the facing area between neighboring vanes. The location of the slit is determined by the mathematical model. Experiments show that the method successfully reduces keen noise by as much as 8 dB.

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The experimental and numerical investigations were done in a vertical pipeline 8.5m in height and with an inside diameter of 60mm. The densities of particles are 982kg/m³ and 2193kg/m³, respectively and both particles consist of spherical plastic balls 6mm in diameter. The profiles of particle velocity and number flux of particles were measured by using a high-speed video camera. Several cases were studied in which the particles of two different densities were mixed for different mixing ratios and in which the uniform density particles were used separately. It is found that the mean velocity of large density particles is increased due to the collision with the small density particles of higher velocity with an increasing feed rate of particles, and that the relative velocity between two different particles is almost constant above a certain number feed rate of particles, and that for a given particle feed rate the larger the mixing ratio of large density particles is, the smaller the relative velocity is. It is also found that the additional pressure loss can be predicted by our simulation.

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This paper investigated flow and its oscillatory behavior in the intersecting region of converging/diverging flow pairs. Flow control was performed by placing a turbulence mesh at the flow exit inside one of two upper flow supply tanks. The angles of converging flows and of subsequent diverging streams were varied. Velocity-vector and power spectrum distributions were obtained by LDV. It was then used to calculate the distributions of vorticity, turbulence intensities in the longitudinal and lateral direction, and Reynolds stress. Of importance is the velocity variation along the shear layer in the intersecting region. This exhibits a peak, referred to as the energy supply point, downstream from the center of the shear layer. Hence, the total kinetic energy resulting from the collision of two converging streams which occurs between the converging point and the peak is released over the range between the peak and the diverging point. This is the sole basis for evaluating heat transfer performance of a flow network. This observation is further strengthened by the power spectrum distribution.

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In this paper we describe the flow associated with three-dimensional surface-mounted rectangular cavities. The experiment was carried out in two types wind tunnel and water channel. A significant aspect of the study has been an examination of the effects of changing the flow incidence angle from 0 degree to the normal from the cavity major axis to 90 degrees. The cavities investigated have had sectional geometries with width/depth of 1.0 and planform aspect ratio of length/width equal to 9.5. The time mean surface pressure distributions, mean velocity inside cavities, and mean velocity and turbulent intensity in the immediate wake of the cut-out were measured as the flow incidence angle was varied. The flow pattern inside cavities was observed by flow-visualization. Consequently it was found that (i) the greatest disturbance to the cavity flow occurs when the flow incidence angle is approximately 75 degrees to the longest cavity axis, and (ii) this is reflected in a large asymmetric wake associated with an increase in cavity drag.

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The aim of the present study is to suppress the fluid forces acting on two square prisms in tandem arrangement, which is found in many cases in structures on land and in the ocean, by exerting passive control on an approaching flow using a small flat plate. The position of the control plate and spacing between two prisms are systematically varied, and then the reduction of the time-averaged and fluctuating fluid forces acting on two square prisms is determined. In addition, the mechanism of the flow control, the structure of the controlled wake, and the behavior of the controlled surroundings flow are discussed in detail based on the surface pressure distributions, the fluid foces and the visualized surface flow patterns.

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The blood flow in large arteries is commonly analyzed by means of the constitutive equations. However, it is not appropriate to use constitutive equations for small arteries because of the heterogeneity of the blood. In this paper, a new method to model an erythrocyte by using beads and springs is proposed as an alternative to analyze the blood flow. The behavior of a single erythrocyte is computed under a constant shear field. The rotating attitude of an erythrocyte, shear viscosity, normal stress difference coefficient and stress thinning are discussed. The results show that the bead-spring model appropriately can simulate the tank tread motion of an erythrocyte under a high shear field and stress thinning. It is therefore considered that the bead-spring erythrocyte model is able to consistently express blood characteristics.

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The heat transfer characteristic of a rectangular channel rotating about a parallel axis in a high centrifugal acceleration field, which is used for field-coil end cooling of a turbine generator, is measured. The aspect ratios H/B of the channel are 6, 30, and 60. The channel wall are heated in full of the cooling perimeter in the case of H/B=6 and in half of that in the case of H/B=30, 60. For the measurement of the heat transfer, a test stand with a model rotor of 〓750mm outer diameter was made. The range of rotating speed of the model rotor in from 800 to 3000rpm, which corresponds to 200-2700 times that of gravity. It is found that the heat transfer is mainly controlled by fluid velocity and in weakly affected by buoyancy near by wall which is represented by Rayleigh number. In the experimental range of H/B from 6 to 60, the measured heat transfer characteristics are almost equal to that which is already reported about a round pipe.

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It is well known that as decreasing the nozzle to plate spacing considerably the heat transfer coefficient of circular impinging jet, which impinges to the plate normally, increases remarkably. At that time, the flow resistance of nozzle-plate system also increases rapidly. In this study, in order to reduce the flow resistance and to enhance the heat transfer coefficient of the circular impinging jet with a considerably low nozzle to plate spacing, a special nozzle with notches is proposed, and considerable improvement of the flow and heat transfer properties are shown. The mechanism of enhancement of the heat transfer properties is also discussed.

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The present paper has dealt with a new method of defrosting by using the frost sublimation phenomenon which occurs below the triple point of water (273.16K, 610.5Pa). The present experimental study has focussed to examine the mass transfer of the annular frost layer developed on a cooling pipe exposed to an impinging jet flow. Morphology of the frost layer during sublimating was observed by using a CCD camera. It was understood that the mass flux of the frost layer increased with increasing the jet flow velocity and the difference of the mass concentration of water vapor between the frost surface and the inpinging jet flow. The nondimensional correlation equations of mass transfer of defrosting were derived as functions of various parameters.

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Local heat transfer coefficients between a constant-heat-flux flat plate and an impinging two-dimensional jet were measured. Most quantitative experimental work to date has been done with impinging at a right angle. The purpose of this paper is to present lateral variation of heat transfer coefficients produced by the impingement of a two-dimensional jet on an oblique flat surface. Heat transfer rates were measured as a function of nozzle size, air flow-rate, nozzle-to-plate spacing, and inclination of the plate. When the plate inclines, the maximum heat transfer coefficient becomes slightly smaller, and the position where the heat transfer coefficient is maximum, shifts to the subsidiary-flow side. The maximum heat transfer coefficient and lateral variation of local heat transfer coefficients are correlated in relatively simple terms.

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Experiments of natural convection heat transfer from central cylinder in a single horizontal array to air were carried out using copper cylinders with d=50.8mm in diameter and 500mm in length. Five cylinders heated isothermally were placed parallel to each other with an equal distance. The spacing of the cylinder array was widely varied from p/d=1.01 to 1.75, where p is the cylinder-to-cylinder pitch. Local and average heat transfer from the central cylinder in the array were measured by means of Schlieren optical and calorimetric methods, respectively.

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For clarification of the mechanism of heat and mass transfer in the early stages of superheated steam drying which accompanies condensation and evaporation, we had done both the experiments and the simple calculation for a semiinfinite heat transfer model. And we found the existence of "reverse point" at which neither condensation nor evaporation occurs in the early stage of superheated steam drying. In this report, in order to investigate the physical reason of the reverse point and its change according to the shapes of heat transfer model, similar analytical and experimental methods were applied for both a spherical and a large slab heat transfer models. As a result, restoration time changes in the range of 3.2∼10times the reverse time with changes of scale, heat transfer rate and initial temperature of the heat transfer models.

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This paper deals with the separation behavior of a press-molded glassware from the pressing mold surface. Since the separation of the glass from a mold surface affects the transcription of the glass shape from the mold, it is desirable to control the separation behavior in the practical press-molding of glassware. In this paper, paying attention to that the separation or sticking of the glass is mainly influenced by thermal pressing conditions in practical molding, separation forces during the demolding process between glass and mold were measured under various pressing conditions. The results showed that, under the certain conditions, the glass sticks on the pressing surface of the mold even after the mold is removed from the pressed glass, and that the separation (sticking) force increases with rising initial temperature of glass and mold, increasing the pressing pressure, and with elongation of pressing duration. In order to translate the obtained results, the separation forces were correlated to the interface temperature between glass and mold at the end of pressing process. The correlation showed that the sticking force becomes evident when the interface temperature exceeds a certain temperature for whole experiments. Under the experimental conditions, the threshold temperature was about 660°C, and is slightly lower than the "softening temperature" of the glass used. From the results, it was concluded that the separation behavior of a press-molded glassware is dominated by the interface temperature between glass and mold at the end of pressing process.

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A theoretical study has been made of film condensation in helically-grooved, horizontal microfin tubes. The annular flow regime and the stratified flow regime were considered. For the annular flow regime, a previouly developed theoretical model was applied. For the stratified flow regime, the height of stratified condensate was estimated by a modified Taitel and Dukler model. For the upper part of the tube exposed to the vapor flow, numerical calculation of laminar film condensation considering the combined effects of gravity and surface tension forces was conducted. The heat transfer coefficient at the lower part of the tube was estimated by an empirical equation for the internally finned tubes developed by Carnavos. The theoretical predictions of the circumferential average heat transfer coefficient by the two theoretical models were compared with available experimental data for four refrigerants and four tubes. Generally, the annular flow model gave a higher heat transfer coefficient than the stratified flow model in the high quality region, whereas the stratified flow model gave a higher heat transfer coefficient in the low quality region. For tubes with fin heights of 0.16-0.24mm, most of the experimental data agreed within ±20% with the higher of the two theoretical predictions.

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If a flow obstruction such as a spacer is set in a boiling two-phase flow within an annular channel, the inner tube of which is used as a heater, the temperature on the surface of the heater tube is severely affected by the existence of the spacer. In some case the spacer has a cooling effect, and in the other case it causes the dryout of the cooling liquid film on the heating surface resulting in the burnout of the tube. In the present paper we discuss the temperature distributions near the spacer and its fluctuation characteristics in relation to the change of the flow configuration near the spacer.

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This paper describes the displacement and deformation of a liquid drop exposed to an airstream. Experiments were conducted using a 60mm×150mm cross-sectional and 500-mm-long horizontal air-suction wind tunnel. Water was fed to a nozzle attached to a vibrator. Dripping uniformly sized drops from the nozzle or uniformly sized liquid drops produced by a longitudinal vibration of the nozzle were used. The displacement and deformation of liquid drops exposed to airstreams were measured from photographs obtained by triple exposure photography or consecutive photography. The liquid drops exposed to airstreams are deformed ; that is, the longitudinal drop diameter, which is the normal size to the airstream direction, the transverse drop diameter, which is the parallel size to the airstream direction, and the curvature of a drop at a stagnation point are changed. The projected area of a drop exposed to airstreams is expected to greatly influence such factors as the displacement, the drag coefficient, and the breakup time ; therefore, the longitudinal and the transverse drop diameters were measured in detail. As a result, the relationship between exposure time of a drop in airstreams and changing drop sizes was obtained.

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These days, epoxy resin is applied to manufacturing of more compact and thinner components for package of electronic devices and others. Epoxy resin has superior properties for heat resistance, insulation and strength, however, defects such as deformations and cracks often occur because of stress concentrations. It is important to know inner stress for resin solidification in molding processes. By combination of numerical analyses of heat rises due to chemical reactions with the experiments of shrinkage and strain measurements for hardening epoxy resin, it becomes possible to analyze hardening shrinkage stress. The developed analysis method contributes to realizations of high reliability for components made of epoxy resin.

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The atomization model of the liquid jet injected from a coaxial airblast atomizer was newly proposed. The atomization model is based on the JE technique. The disturbance wave on the liquid jet surface grows according to the linear instability theory, and the droplets detach from the surface wave when the wave amplitude exceeds the critical value. The liquid jet itself disintegrates into a liquid clump when the amplitude of an asymmetric wave exceeds the critical value, and the liquid clump disintegrates again into finer droplets according to the TAB model. The calculated breakup length shows the smaller value compared to the empirical equation, especially at low air velocity. The Sauter's mean diameter calculated from the model almost coincides with the Nukiyama-Tanasawa's equation at high air velocity. However, at low air velocity the calculated mean diameter shows much larger value compared to the equation.

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Both flame propagation speed and droplet cluster disappearance speed in a premixed-spray burner system are experimentally investigated by image processing analysis in an effort to evaluate two-stage flame structure observed in the premixed-spray flame. It is confirmed that flame speed concerned with premixed-mode combustion in the spray flame is approximately 2.0m/s in average while mean disapperance speed of droplet clusters, which are dominated by diffusion-controlled combustion-mode downstream of the flame, is evaluated as much as 0.45m/s. Although both speed, which are supposed to depend on local properties of the spray itself and flow conditions surrounding droplet clusters, are scattered in experiments, it was clarified that both characteristics of premixed-mode and diffusion-mode combustion in spray flames are of much difference in nature.

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The advanced steam turbine systems with the Ultra Super Critical pressure steam condition will be effective for replacement of the old oil fired existing power plants. By application of this advanced steam turbine systems, CO₂ emission will be reduced by 10 percents and also the generating cost will be improved by 20 percents. This report describes optimization of this turbine systems and economic evaluation compared with the conventional super critical pressure units.

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The measurement of low fluid velocity due to natural convection is tried in a vertical annulus by a method using a tracer of heated air (a thermal pulse technique). This technique is firstly used for measuring the velocities from 0.1m/s to 1.0m/s in laminar forced convective flows in a vertical circular pipe, and its availability is verified. Secondly, the method is applied to natural convective flows in the vertical annulus at the Grashof numbers from 10³ to 10⁴. The measured velocity distributions in the radial direction are in a relatively good agreement with those of numerical computations.

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