Over 90% of Subarachnoid hemorrhage is caused by rupture of a cerebral aneurysm. The medical statistics indicate that the cerebral aneurysm occurs predominantly in the arteries branching off with a sharp curvature where the flow and wall shear stress change abruptly. In this paper, a system for analyzing the flow in the cerebral artery has been constructed. In this system, a numerical simulation have been conducted for a geometry, which is extracted from computed tomographic angiography of the cerebral artery. The boundary conditions, which is modeled from measured data is prescribed to simulate the hemodynamics in the real situation. This system investigates an effect of geometry on the wall shear stress distribution and the flow pattern in the artery. As the result, the wall shear stress concentrates on some specific areas due to the effect of the curvature.

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Two-components fluids have played an important role in a variety of industrial devices. In particular, it is very important to describe the interactions of gas and liquid at the interfaces of various flow patterns. Such behavior used to be solved numerically by a set of finite difference equations. However, numerical simulation of interfacial motion in a flow is still incomplete in many cases. The cellular automaton method is expected to be an effective numerical technique for simulating such a complex fluid motion as separation and mixing. The cellular automata method follows the mesoscopic particle dynamics with simple rules. These enable us to realize discrete molecular dynamics on the computers with a large freedom. It was demonstrated that an automaton solution simulated the phase separation and mixing at its interface. After evaluation of the velocity distribution of the averaged solution, it can be concluded that the lattice gas automata method is useful to simulate two-component fluids flow.

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The present study explores numerically the differences in flow patterns and oscillatory momentum transport in three grooved channels with different cavity lengths for pulsatile flow. Numerical simulation by the Finite Element Method is performed for the same parameters as the previous experimental conditions, i.e., the net flow Reynolds number Re_s=234 and the oscillatory fraction of the flow rate P=0.43. In particular, the effect of the imposed frequency is considered in the Strouhal number range of 0.2 to 2.8. The vortex strength for the shortest cavity has a peak at the imposed frequency close to the natural one for self-sustained oscillation, i.e., St_n=1.92. While the Strouhal number for the maximum strength is reduced as the cavity length becomes large. It is found that the momentum transport due to the oscillatory components of the flow plays a dominant role in the vortex strength. Fluid particle ejection from the groove is also examined to represent fluid mixing characteristics. The trend for particle ejection corresponds well to the vortex strength. Additional flow visualizations support the numerical simulation.

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Three-dimensional high-definition particle tracking velocimetry (3-D HDPTV) is successfully applied to simultaneous measurement of fluid and dispersed phase in a vertical turbulent water channel flow. On average, 400 and 200 velocity vectors are simultaneously obtained for tracer and solid particles, respectively. Turbulent statistics are substantially modified by the solid particles having a diameter of 2-3 times the Kolmogorov length scale. When the turbulent intensities are nondimensionalized with the wall friction velocity, the streamwise component of the fluid phase is significantly increased at the center of the channel, whilst it is unchanged at y⁺<20. Since the turbulent production due to shear is unchanged by the presence of the dispersed phase, the turbulence energy should be directly generated by the wake of solid particles. The quadrant analysis shows that the solid particles are densely distributed along the low-speed streaks, especially beneath the ejection event. The difference in traceability of particles to the ejection and sweep events should contribute to the particle agglomeration.

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Terminal velocities of single solid particles or bubbles are one of the most fundamental knowledges required for modeling and simulation of dispersed two-phase flows in vertical pipes. However, there are few available correlations which can cover a wide range of parameters, i.e., the ratio of a particle diameter to a pipe diameter, particle density as well as the falling motions of particles such as rectilinear and rocking. In this study, we proposed a semi-empirical model of terminal settling velocity which can cover a wide range of parameters, based on a singular pressure loss about a particle. Experiments were also carried out to develop an empirical correlation based on the proposed semi-empirical model of terminal settling velocity of a particle falling through a liluid-filled pipe. It was confirmed through comparisons of terminal velocities between the measurements and the developed correlation that the proposed model can give good estimations of terminal velocities under various terminal settling conditions.

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It is most important factors that were dealt with the size and production frequency of formed bubble and the rising state of bubble in the distributor vicinity at a solid-gas fluidized bed for the mixing and reacting process of the fluidized bed. Especially it is more complicated in the case of the pressurized fluidized bed. In order to understand the mechanism and behavior of the formed bubble, the investigations on the shape and flow characteristics of the formed bubble in a pressurized bed was carried out and bubbles were formed at a single nozzle in the pressurized solid-gas fluidized bed with distributor. Experimental data were obtained from visualized image of the bubble using the shadow-graph method and were analyzed. Those results indicate that the size and rising velocity of bubble were increased with relation to increase of the nozzle flow rate and these bubble behavior were varied with increase of the pressure in bed.

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It is important for the realization of two-phase flow thermal control system to clarify the two-phase flow behavior under microgravity condition, especially an annular flow, which is the main flow pattern in the two-phase flow thermal control system. In order to evaluate the effect of the gravity and the surface tension of liquid phase on the liquid film structure, the experiments for an adiabatic gas-liquid two-phase flow in a vertical tube of 10.5 mm in I.D.were carried out under a variety of gravity condition obtained by utilizing a parabolic trajectory flight of an airplane and a drop tower. Gaseous nitrogen and water were used as the working fluids. Furthermore, to decrease the surface tension of the liquid phase, sodium oleate was added into the water. As a result, it was shown that for the higher gas velocity the effect of gravity on the liquid-film thickness was lower, however for the lower gas velocity the liquid-film thickness under microgravity became thinner than that under 1 G.

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An upwind gridless type solver has been developed for the compressible Euler and Navier-Stokes equations. Points are flrst distributed all over a computational domain. The spatial derivatives of the governing equations are estimated at each point using its cloud of points. An upwind method using Roe's approximate Riemann solver is adopted for the estimation of the inviscid flux. The linear system derived from temporal implicit approximation is solved using LU-SGS method. Validity of the solver has been examined with a series of numerical experiments for two-dimensional inviscid and viscous flows. The solver can work on structured grid points, locally refined Cartesian grid points, unstructured grid points, and any points distributed with arbitrary manners. The numerical results obtained for test cases, including flows over four-element airfoils, are in good agreement with corresponding exact solutions, available numerical results and experimental data.

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It is important to understand the heat transfer and flow in an automotive headlamp in order to improve heat proof ability, durability and ventilation performance. Especially in the disign stage, understanding thermal air flow inside the headlamp will make it possible to shorten its development period, which can be fulfilled by Computational Fluid Dynamics (CFD) technique. In the present study, a newly-developed method called surface heat transfer (SHT), that is a unique technique for making an accurate estimate of temperatures in the automotive headlamp without coupling fluid and structural mechanics, was investigated for practical use. An evaluation of CFD results was performed and compared with the experimental results. Consequently, the temperature results by CFD were within ±10 degrees as compared with the experimental results.

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In this paper, similarities of flow characteristics and self-excited oscillation characteristics of collapsible tubes were studied. Experiments were carried out for three kinds of tube that had various thicknesses and inner diameters, as parameters of downstream transmural pressure and flow-rate. Natural frequencies of the tubes were measured experimentally in the non-flowing condition. Moreover, the natural frequencies of the tubes were calculated by the simple analysis. The characteristics of collapsible tube are greatly different in the low and high flow-rate stages. In the low flow-rate stage, even if the tube inner diameter or the tube thickness is different, we found similarities of the flow and self-excited oscillation characteristics. Frequency of self-excied oscillation is nearly equal to the natural frequency in the low flow-rate stage.

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This paper presents a theoretical analysis for the hydrodynamic pressure induced by the rotating vibration of the skinplate of Tainter gates on Folsom dam in California. The curved skinplate and dam crest were replaced by the straight line to simplify the flow boundary. The reservoir flow fluctuation induced by the skinplate vibration with a small amplitude was analyzed for the zero gate-opening, by a potential flow theory developed for dissipative wave radiation problems. Thus, the hydrodynamic pressure exerted on the skinplate was derived in a non-dimensional expression, and its major characteristics were revealed.

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In the present paper, the velocity profile, the wall shear stress and its gradient at the apex of the anterior communicating artery are described in pulsating flow. The anterior communicating artery composing the circle of Willis is one of the predilection sites where the cerebral aneurysm occurs frequently. The flow around the anterior communicating artery is simulated by two confluent tubes joining at the angle of 60 degress, two parallel bifurcating tubes, and the junctional tube, bypass, connecting four tubes. The velocity profile is clarified around the apex where the cerebral aneurysm is apt to initiate. In particular, the gradient of wall shear stress around the apex at one confluent tube with much flow rate is estimated, and the relation between the gradient of wall shear stress and the initiation of aneurysm is discussed physiologically.

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The existing lifting-line theory for a supercavitating hydrofoil in both vertical and spanwise shear flow between two parallel planes is applied to partial cavitation in the same flow condition. A lifting-line equation is derived from combining the assumption holding lift coefficient two-dimensional at any spanwise position with the up-wash velocity distribution induced along a lifting-line. The hydrofoil for the numerical example is flat in section, rectangular in planform, and 5 degree in attack angle. Effects of two kinds of shear parameter, cavitation number, and taper ratio on local life coefficient, total lift coefficient and induced drag coefficient are clarified through the numerical calculations. The cavity length distribution is obtained on the basis of the assumption holding the pressure within cavity two-dimensional at any spanwise position.

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We have developed a new mixing method for micro-liquid. It is well known that the free surface of a liquid is pushed out when ultrasound propagating in the liquid reaches the free surface. This phenomenon is due to the radiation presure caused by ultrasound. In the new method this pressure is used to mix liquid in a vessel without the need to contact with the liquid. The developed mixing system based on this method consists of a vessel that liquid to be mixed and two ultrasound sources (frequency : 1.6 MHz) arranged outside the vessel. One of them radiates through the bottom, the other through the side wall of the vessel. The latter sound source is divided into several segments. And the fine position of the sound source corresponding to the level of liquid is adjusted by selecting the appropriate segments. The mixing performance is evaluated according to the difference between the Two local transmissibilities of laser beam in the liquid. As a result, we confirmed that by using our mixing method, the liquid(water:80-160 μl and dye:4μl) became homogeneous within 1.0 s.

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The mechanism of propagative collapse of a vapor film at high wall superheat and the effect of a local-cold spot on the minimum-heat-flux(MHF)temperature and collapsing fashion in film boiling were investigated experimentally and analytically. Using a 1 mm diameter and 160 mm long platinum wire, pool film-boiling experiments were performed for saturated or subcooled water at atmospheric pressure. In the experiments, temperatures of electrodes which served as the cold spots of the test section were varied in a range from 250 to 450 °C. Experimental results showed that the propagation velocity of vapor film collapse decreased and the MHF temperature increased with a decrease in the local-cold spot temperature. In particular, when the local-cold spot temperature was lower than the thermodynamic limit of liquid superheat, the MHF temperature increased remarkably. Application of the Yamanouchi model for rewetting of a hot surface by a falling film to the present vapor film collapse was successfully tested by including conventional MHF-temperature and critical -heat-flux correlations. Furthermore, a more precise model was developed by coupling heat conduction and a full boiling curve as the boundary condition. The propagation velocities measured were well represented by this model. It was proved that local temperature at a collapsing front of the vapor film, that is the local solid surface temperature at the initiation of liquid-solid contact, never exceeds the thermodynamic limit of liquid superheat even if the collapse of the vapor film occurs at high wall superheat.

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A multiple pass heat exchanger composed of pipes and plate fins has a typical structure of the heat exchangers used for melting snow. In this study, we discussed the characteristic of the multiple pass heat exchanger having two types, a regular interval type and an irregular one, focusing on pipe pitch of the multiple pass heat exchanger. The perfect melting condition and the melting efficiency were related to dimensionless parameters for the heat exchanger and its operating conditions. The calculated results for the perfect melting condition and the melting efficiency agreed with the results obtained from the field tests on melting of falling snow. Applying the irregular interval leads to extend the critical condition of the perfect melting when the flow rate of brine is low or the area for melting of falling snow is wide. Also, the melting efficiency of the irregular interval becomes higher than that of the regular interval. The optimum pipe pitch was obtained, connecting with the maximum values of the critical condition of the perfect melting.

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Condensation heat transfer in a closed two-phase thermosyphon is experimentally examined using two different types of test section. Test Section 1 is a straight pipe type thermosyphon and Test Section 2 has a large diameter evaporator compared with a condenser to minimize entrainment from the evaporator. Condensation heat transfer in Test Section 1 shows much lower heat transfer than the Nusselt theory. This low condensation heat transfer occurs due to working fluid entrainment. It is confirmed from a result of Test Section 2 that the condensation heat transfer is similar to the Nusselt theory as far as the effect of working fluid entrainment is negligible and the flooding does not occur. A new correlation for the heat transfer coefficient considering the effect of entrainment is proposed.

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The present study deals with fluid flow and heat transfer in the transition process of natural convection over an inclined plate. In order to examine the mechanism of transition, experiments on the flow and heat transfer were performed for various plate inclination angle in the range of 20°∼75°. The wall temperature and fluid flow fields were visualized using a liquid crystal sheet and fluorescent paint, respectively. It was confirmed from the visualization that the separation of the boundary layer flow takes place and the beginning point of streaks appears over the plate wall when modified Rayleigh number exceeds characteristic value for each inclination angle. The local Nusselt number in the transition range were proportional to one-third power fo local modified Rayleigh number. By introducing a nondimensional parameter, the correlation between visualizations of the flow and temperature fields and heat transfer is rearranged quantitatively.

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The distribution of gas and liquid in gas-liquid two-phase slug flow was measured using semi-supermultiple point-electrode probes. Based on the measurements, the wake zone behind the gas slug and the low void fraction zone in the liquid slug are defined and the void fractions of the two zones are determined. The data reveals that the void fraction of the wake zone increases according to J_g, while there is little dependence. On j_ι. Non-dimensional head is proposed in consideration of the momentum change of the liquid in the wake zone. It is clarified that non-dimensional head is closely related to the void fraction of the wake zone. A good practical relationship is found between non-dimensional head and the lengths of the swelling liquid front zone and the wake zone, and empirical correlations are proposed for the void fraction in the wake zone, the mean void fraction in the liquid slug, and the lengths of the swelling liquid front zone and the wake zone.

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In this paper, the authors propose a novel technique for controlling the birefringence in the surface region of polymer injection-moldings as a described "pattern" by utilizing interfered laser irradiation. In general, surface region of the injection-molded polymer products inherently contain large birefringence due to molecular orientation, since the high-temperature polymer melt is suddenly cooled in its surface region by the unsteady heat transfer to the cold mold wall during the melt flows within the mold cavity. The proposed technique controls the unsteady heat transfer by utilizing heat generation within the polymer in the surface region due to interfered laser irradiation, so as to reduce generation of birefringence as a pattern. The effects of molding and irradiation conditions on the recorded birefringence pattern were examined both experimentally and numerically, and the results clearly showed that the recordability of the birefringence pattern is dominated by the thickness profile of low-temperature region appeared on the polymer surface adjacent to the mold wall due to interfered laser irradiation.

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Experimental studies were carried out to clarify the flow characteristics of liquid films of an annular two-phase flow in a curved double tube;visual observations of liquid film and measurements of film flow rate. Based on these experiments, mechanisms of the formation of annular liquid film in a curved double tube were discussed as follows. The liquid phase moves toward the outside region by the disturbance wave and returns toward the inside region by the base liquid film. The driving force of the former is the centrifugal force acting on the disturbance wave, while the driving force for the latter is the shear force caused by a secondary flow in the gas core.

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One of the most difficult and critical factors in modeling of boiling phenomena is the bubbling behavior of nucleation sites. In this work, a single artificial cavity was manufactured on a Cu thin plate and was heated by laser irradiation in a water pool with saturated boiling condition. Three types of artificial cavities were tested, which of those were conical, cylindrical and reentrant. Conical cavities showed highly intermittent bubbling with large temperature fluctuations and required rather high superheat to maintain bubbling. Phase map was reconstructed from the temperature time series and revealed rather simple structure of bubbling. Further nonlinear analysis was carried out and strong possibility of the existence of low dimensional deterministic chaos was indicated. Cylindrical cavities showed continuous and stable bubbling from a rather low superheat. Only small temperature fluctuations were observed and return map was constructed from succeeding bubbling interval, showing from simple to highly nonlinear bubbling behavior. Reentrant cavities showed similar behavior to those of cylindrical type, but little more complicated.

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This paper has dealt with the sorption characteristics of honeycomb shape type sorbent element composed of new organic sorbent which was composed of the bridged complex of sodium polya-crylate. The transient experiments in which the moist air was passed into the honeycomb type sorbent element were conducted under various conditions of air velocity, temperature, relative-humidity and honeycomb length. As a result, the effective mass transfer coefficjent of the organic sorbent sorbing the water-vapor was non-dimensionalized as a function of Reynolds number, modified Stefan number and non-dimensional honeycomb length.

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This research tried resource recovery of the waste wood and effective utilization. In our study, we used walnut as waste wood. We distillated walnut in dry distillation boiler, changed walnut charcoal. Then, we recovered heat energy that is generated in the time, and attempted the effective utilization of energy. And, we utilized the property of the charcoal of the porous body, produced walnut charcoal as an inner-wall breathing material, and tired the improvement in the indoor environment. The conclusion were as follows; 1)If we distilled walnut, we produce walnut charcoal, which is 28% of the walnut's mass in simple distillate experiment. 2)If we distilled walnut, we produce walnut charcoal, which is 15% of the walnut's mass in dry distillation boiler. 3)The heat recovery rate of dry distillation boiler is 17%. The heat recovery of walnut produce 5.26 [MJ/kg], which is 12% of the quantity of heat of walnut. 4)Inner-wall breathing material of walnut charcoal have dehumidification and spout moisture effect. 5)Inner-wall breathing material of walnut char-coal cut indoor overall heat transfer coefficient for 55%. 6)Inner-wall breathing material of walnutcharcoal has aerial purification performance by the residual wood vinegar component in the inside the walnut charcoals.

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The humidification system in a PEFC is handicapped by the water management under a range of temperatures including low temperatures in winter, so the performance with and without humidification was considered and simulated for a variety of fuel cell temperatures. The characteristice of a single cell with a cell area of 104 cm² was identified by experiments and a one dimensional model was developed to evaluate cell performance. The experiments found that water managements are important because the ionic conductivity of the membrane and catalyst layers decreases when there is little humidity. Results of start-up tests with the cell showed that the fuel cell recover the performance quickly in temperature as low as 10°C. The one dimensional simulation model showed that the measured cell performance agrees with the modeling results for various humidity conditions of the cell. If low reaction temperatures and low current densities are selected as operating conditions, it would be possible to apply the dry system at the start-up.

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Combustion characteristics of a tubular flame burner, which has been developed previously for propane, have been investigated with using methane as a fuel. The results show that the combustion characteristics for methane are almost the same as those for propane. Namely, (1)the equivalence ratio at the lean limit is about 0.5, (2)the wall temperature at the injection section is kept low, and (3)the burned gas temperature is uniform in the axial direction. However, (4)a tubular flame with a large laminar flame area of 0.24 m² is obtained with lean mixtures, (5)the stable flame region in the fuel-rich side is very narrow, (5)the equivalence ratios at which the flame diameter, the flame length, and the flame temperature take their maxima or minima are shifted to 0.9, and (6)the volumetric burning rate becomes 50% less or more than the total mixture volume flow rate for the near lean- and rich-limit mixtures, although they agree well for the stoichiometric mixture.

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Simultaneous reduction of NO_χ and smoke under high load conditions could be obtained by MULDIC(MULtiple stage DIesel Combustion) where mixture was made stratified before ignition. In this investigation of the basic characteristics of MULDIC, gaseous fuels (DME, Propane) were charged into the intake air which led to the creation of homogeneous lean mixture, and liquid fuel was injected into the cylinder and made rich mixture. The results of the engine test showed that NO_χ emissions could be reduced to less than 100 ppm and smoke emissions were also maintained 0 FSN even at higher loads. Moreover, homogeneous rich mixture test results showed that low smoke combustion could be obtained under equivalence ratio of 1.6. In MULDIC, increasing the ignition delay period of injected fuel, soot formation rate was decreased, because over rich region was avoided.

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Using a model burner, spray flame was investigated for the fundamental case of laminar and axisymmetric conditions and at low load. The experimental data were compared with the calculated results by a numerical code(Fluent Ver.4.3). In the model burner, Kerosene/air spray was generated by an airblast atomizer and ignited by annular and central pilot flames. The range of flame stability, the distributions of temperature and species concentrations (CO₂, O₂, CO, NO_χ and total hydrocar-bons), and the velocity, mean diameter and number density of fuel droplets were measured. A phase Doppler velocimeter was used to measure the behavior of fuel droplets. Both temperature and the concentration of CO₂ are higher downstream of the flame and in the recirculating zone surrounding the flame. Fuel droplets are accelerated as the evaporation and combustion proceed, while their Sauter mean diameter is not changed significantly. Although the predicted temperature values are higher by 200∼300 K than the measurements, the trend of the temperature variation is reproduced well by the calculation. The concentration distributions of CO as well as of CO₂ are predicted fairly well despite the simplified two-step reaction scheme. The calculated droplet trajectories are also in fair agreement with the measured behavior of fuel droplets.

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We discussed the flame structure of piloted lean turbulent premixed flames, equivalence ratios of which were around the lean flammable limit. Laser tomography, chemiluminescence detectors, LDV and a thermocouple were used simultaneously for observing lean turbulent premixed flames with silica powder seeded. As a result, the transition of flame structure from a distributed reaction zone to a wrinkled laminar flame was observed in detail with the observing position being traversed from upstream to downstream.

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To study system configurations and operation conditions of a Solid Oxide Fuel Cell (SOFC)/Gas Turbine (GT) combined cycle power generation system, system analysis was carried out by means of numerical simulation method. In the system analysis, the performance of SOFC was simulated with the expected SOFC module performance. This report discussed the influence of the SOFC operation conditions, such as fuel utilization and current density, on the efficiencies based on the output of the gas turbine and the system. As a result, it is clarified that elevating the SOFC operation pressure is effective for improvement of system performance, mainly because the GT performance becomes higher. The system efficiency is estimated at around 60% (HHV) at 0.98 MPa of SOFC operation pressure.

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System analysis of Solid Oxide Fuel Cell (SOFC)/Gas Turbine (GT) combined cycle power generation systems were carried out by means of numerical simulation method. In the first report, the influence of the SOFC operation conditions on the efficiencies of the system was discussed. This report studied the influence of the system configuration on the system performance. First, the system performance using internal reforming was compared with that using external reforming. Next, the system performance using cathode gas recycling or anode gas recycling was studied. As a result, it was clarified that the use of the internal reforming or gas recycling was effective to raise the gas turbine inlet temperature, but did not always make the system efficiency improvements. However, when the Heat Recovery Steam Generator is installed in the system using anode gas recycling, the efficiency of the SOFC/GT/Steam Turbine combined cycle power generation system was estimated to be over 65%.

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