Two methods of boundary conditions which can be applied to thermal FDLBM models were studied and their performances were evaluated applying bench mark tests. First method, called "control node method", can handle a wide variety of boundary conditions and showed an excellent performance on the test. Although the structure is slightly complicated and it seems rather tedious to make a computing software, this method will promise you accurate simulations. Second method, called "extrapolation method", is an improved version of the method by McNamara. Making a computing software is quite easy and the performance is assured to some extent. It is a viable method if it is not required strict accuracy.

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A numerical analysis technique using the level set method has been developed to calculate the critical velocity of a particle for penetration into liquid. The contact angle, a dominant factor in this phenomenon, is given by a virtual liquid surface inside a solid wall. A Cartesian grid method with immersed boundaries is also applied in order to accurately express the boundaries of a moving particle. Current results agree with other calculated and experimental results in both contact-angle problems and immersed-boundary problems. Finally, calculations of a particle impinging on a liquid surface have been carried out. Current results of the critical velocity agree with the experimental results and theoretical results.

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Simultaneous measurements of pressure gradients and spatio-temporal characteristics of gasliquid interface are conducted in vertical upward two-phase flow. To clarify the mechanism of frictional pressure losses for slug, churn and annular flow regimes, a hydrodynamic flow model is presented which permits predictions of the frictional pressure gradient for a wide range of flow regimes. The liquid flow structure is assumed to consist of waves propagating upward and base film flow. The contributions of waves and base film flow to the frictional pressure gradients are presented by considering P. D. F. for liquid holdup. At low liquid flow rate, the wave velocity is much higher than the absolute velocity of the base film, and the frictional pressure gradient is dominantly caused by the wave propagation. At high liquid flow rate, the contribution of the base film flow becomes comparable to that of waves. The agreement between the predicted frictional pressure gradients by the present model and experimental data is fairly good.

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An implicit numerical algorithm (C-ISMAC method), which is based on an implicit-SMAC method in the staggered grid, has been proposed for free-surface flows with the collocated grid system. It has been shown that a CBP (Cell-Boundary Pressure) scheme, which utilizes Pⁿ on cell boundaries in the prediction stage of the MAC method, is effective to deal with the pressure field. Taking account of this result, some distinctive treatments for the pressure variable were employed in developing the C-ISMAC method. As a result of the computations in cavity flows and free-surface flows, it was shown that the C-ISMAC method enables us to use higher-order spatial schemes as well as to decrease the necessary computational time.

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To develop a simulation software which is able to predict the filling processes of a nematic liquid crystal into a liquid crystal cell, we present a basic model for the filling processes and its computational procedure. The Leslie-Ericksen theory is used as a constitutive equation, and the Hele-Shaw approximation is applied in order to simplify the modeling and to reduce computational power. We also employ a reasonable approximation concerning the director, where the director is not affected by the velocity distribution, but is determined uniquely by the director angle anchored on the liquid crystal cell walls. Input data are cell size, position and size of injection holes, anchoring angles of the director, and viscosities of a liquid crystal. The software can predict free surface lines to move upwards smoothly with time, and effects of the input parameters on the filling time are numerically evaluated.

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Bead-spring macro model is proposed as a new method to analyze a viscoelastic flow. The tetrahedral structure of beads and springs models a gathering of intertwined polymer chains, and the interaction between gatherings is considered. Poiseuille flow of polymeric liquid is computed simultaneously with the behavior of the bead-spring structure. The numerical results are compared with the experimental results. The results show that the bead-spring macro model can consistently express rheological properties of polymeric liquid such as non-Newtonian viscosity and normal stress differences. Besides, the present model can easily explain the flow field and the stress tensor in terms of the macro model condition. It is found that the present model can consistently simulate a Poiseuille flow, which is a flow field with various shear rates and with walls.

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In the former study, in order to predict the temperature in an automotive headlamp without coupling fluid and structure mechanics, SHT (Surface Heat transfer) method has been developed and the temperature estimation accuracy using SHT has been investigated for practical use. Consequently, the temperature results by CFD were within ±10 degrees as compared with the experimental results. The reason of the error was considered with since neither the radiation in the high temperature area nor the three-dimensional movement inside plastic parts were taken into consideration. In the present study, in order to take these movements into consideration, a newly-developed method called FSI-DM (Fluid Solid Interface using Discontinuous Mesh) was developed. This FSI-DM is the method of connecting fluid and solid parts using a discontinuous mesh, and the density of the mesh inside the solid and the fluid can be changeable. Furthermore, the coarse mesh on the surface of the solid enables us to calculate the radiation with a smaller memory capacity.

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The difference of turbulent statistics between compressible and incompressible turbulent channel flows is investigated using the DNS data of the compressible turbulent channel flow between isothermal walls and the DNS data of the incompressible turbulent channel flow. For comparison of compressible and incompressible flows, the dependence of turbulent statistics on the semi-local friction Reynolds number Re^*_τ and the wall friction Reynolds number Re_τ is clarified in the compressible and incompressible turbulent flows, respectively. The semi-local friction Reynolds number is based on the local density and viscosity, semi-local friction velocity, and channel half-width. The main results of this paper are as follows: (1) The dependence of the turbulence intensities of the wall-bounded compressible turbulent flow on Re^*_τ is almost the same as that of the incompressible turbulent flow on Re_τ except for the streamwise turbulence intensity near the wall. The streamwise intensity depends on the Mach number. (2) The reduction in the pressure-strain correlation term suppresses the energy transfer from the streamwise component to the wall-normal and spanwise components. As a result, the streamwise turbulence intensity becomes larger, and the wall-normal and spanwise turbulence intensities become smaller in the compressible turbulent channel flow, comparing with the incompressible one. (3) The reduction in the pressure-strain correlation term is due to the reductions of the RMS velocity derivative fluctuations and the absolute values of correlation coefficients between pressure and velocity derivative fluctuations.

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Three-dimensional numerical simulation is performed of pulsatile flow around a tori-modeled stent inserted into parent artery below a neck of sidewall aneurysm. When blood flow in the aneurysm is suppressed by the stent, thrombus is generated in the aneurysm resulting in prevention of development and rupture of the aneurysm. The mechanism is clarified which the flow is induced in the aneurysm even when the aneurysm neck is covered by fluid-dynamic obstacles of stent filaments. The averaged maximum Reynolds number is chosen as 250 and Womersley number as 2.7. It is shown that flow-inducing sources are pressure difference between proximal and distal sides in the aneurysm neck and kinetic energy flowing into the aneurysm at the proximal side whose direction is turned from axial to radial directions and whose magnitude is reduced due to impingement of boundary-layer flow in the parent artery. Possibility of the thrombus formation on the aneurysm wall is evaluated using the shear rate.

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In order to investigate the supersonic flow phenomena related to internal and external flows of high-pressure gas pipeline systems, new air breathing engines and space planes, a new supersonic wind tunnel (pressure-vacuum type, Mach 2.0 and 4.0) was designed and constructed in Muroran Institute of Technology. The cross section of the test section is 8 × 8 cm², and the working-time of the wind tunnel is 20 s for Mach 4 condition. This paper describes firstly outlines of the new Mach 4 supersonic wind tunnel, and describes secondly the structure and characteristics of the Mach 2 and 4 supersonic flows with pseudo-shock waves in a square duct. The characteristics of the pseudo-shock waves were clarified by color schlieren photographs and duct wall pressure measurements.

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In order to predict and understand the low Reynolds number phenomena observed on wind turbine blades, especially formation of separation bubbles, the flow fields around an airfoil for wind turbines are numerically analyzed in the condition that a separation bubble is observed in wind tunnel experiments. The results from three-dimensional unsteady analysis using a finer grid system show a discontinuity in the pressure coefficient distribution around the airfoil. This discontinuity captures the formation of a separation bubble at a certain location, which shows good agreements with experimental results. From visualization of flow fields, the mechanism of separation bubbles is recognized as follows: after vortex formation and growth in the separated boundary layer, the vortex distortion and transition to 3-dimensionality follow, then the flow field becomes fully turbulent. The power spectrums of pressure field from experiments support this feature.

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This paper describes the results of an experimental study on characteristics of flow and fluid forces acting on two parallel circular cylinders. The Reynolds number was 5.5 × 10⁴ on the bases of a single cylinder. For the spacing T/D<1.1 (T, spacing between the cylinders; D, diameter), the gap flow was biased to one side and intermittently changed over. When the spacing ratio between the cylinders was less than 0.3 the two cylinders formed a single wake behind them. The biased gap flow, for T/D=O.3∼1.1, formed a narrow wake with a Strouhal number higher than that of a single cylinder and a wide wake with a lower Strouhal number. In this region of spacing, when the gap flow switched spontaneously from one side to another, there existed another short duration stable flow (can be termed as intermediate flow) whose Strouhal number was almost equal to that of the single cylinder. The wavelet analysis of the velocity signals obtained with hot wire probes and flow visualization patterns confirmed the appearance of the intermediate flow pattern. Pressure and fluid forces acting the cylinder were decomposed for the narrow wake and the wide wake flow patterns, then fluid forces acting on the cylinders were explained on the basis of time-averaged and fluctuating pressure, fluctuating fluid forces, Strouhal number, and flow visualization.

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This paper describes the stability of a radial liquid sheet experimentally and theoretically. The liquid sheet was formed by the release of a radial liquid-film flowing on a disk from the edge of the disk to still air. When the Reynolds number is large, a concentric disturbance wave ('D wave') appears and grows downstream on both free surfaces of the liquid sheet. To clarify the root of 'D wave', its frequency was measured by a laser beam-reflection method and the cross-section of the wavy liquid sheet was observed by the LIF method. Temporal and spatial linear stabilities of the liquid sheet were also investigated. The frequency and wavelength of 'D wave' and the phase difference between 'D waves' on both liquid surfaces agreed well with those of the disturbance predicted by the stability theory. This means that 'D wave' on the liquid surface is caused by the unstable disturbance, which is attributable to the inflectional veocity distribution of the liquid sheet. It was also found that Gaster's simplified equation, which transforms the temporal growth rate to spatial one in the stability theory, is inadequate for a disturbance of large growth rate.

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The purpose of the study is to examine the validity of J-groove in controlling and suppressing swirl flow in conical diffuser, for draft surge suppression in a Francis turbine which is caused by the swirling flow from runner outlet into a draft tube. "J-groove" composed of shallow grooves mounted parallel to the pressure gradient on the diffuser wall is a very simple passive device to suppress several anomalous phenomena in turbomachinery. The experimental study has been performed using conical diffuser of divergent angle 20 degree. The measured results of velocity distribution in the diffuser show that considerable reduction of swirl intensity is attained by use of J-grooves. Besides, the amplitude of pressure fluctuation caused by rotation of vortex core around the dead water region near the diffuser inlet is reduced by J-grooves.

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In order to obtain the resistance coefficient of the obstacle board in a road tunnel (blockage plates and sign boards), model tests are carried out. As it became clear during the study, that the resistance differs according to the type of the plates, the authors propose three types of empirical formulae as function of the opening ratio, by means of least square method. These formulae can be immediately applied for designing tunnel ventilation facilities.

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The current study describes experimental and computational works on the passive control of the unsteady condensation shock wave which is generated in a transonic nozzle. The bleed slots were installed on the contoured wall of the transonic nozzle in order to control the condensation shock wave. For computation, the two dimensional, compressible, Navier-Stokes equations, fully coupled with the condensate droplet growth equations, were numerically solved by a third-order MUSCL type TVD finite-difference scheme, with a second-order fractional time step. Baldwin-Lomax turbulence model was employed to close the governing equations. An experiment using an indraft transonic wind tunnel was made to validate the computational results. The current computations represented well the experimental flows. From both experimental and computational results it was found that the oscillations of the condensation shock wave were successfully suppressed by the bleed slot system.

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An abrasive water suspension jet (AWSJ) has a greater capacity for drilling and cutting than an abrasive water injection jet (AWIJ). In the present investigation, drilling capability of the AWSJ under submerged condition is studied experimentally with specimens of stainless steel at the jetting pressure of 6 to 18 MPa and the cavitation number of 0.008 to 0.03. The abrasive used in the drilling tests is aluminum oxide with a mesh designation of # 100. The drilling capability of the submerged AWSJ is affected greatly by the cavitation phenomenon around the jet. The drilling capability decreases steeply with the increases of the standoff distance and the cavitation number. Preferable nozzle and nozzle holder shapes are investigated through the drilling tests and observation of the cavitating jets.

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In this paper, an improved method for the estimation of rotational temperature with a weak electron beam is presented. Using the method, the effect of an electron beam on a flow field becomes smaller and it is possible to obtain the distribution of rotational temperature with a smaller experimental apparatus. In the method, slit width of a monochromator is set wider to obtain larger signals for the higher rotational levels. Due to the decrease of resolution, the rotational spectra are measured with much overlapping, but they are divided into their individual rotational spectra by using a fitting function. Using the improved method, a rotational temperature and a relative number density distribution in a supersonic nitrogen free jet expanding from a stagnation temperature of 350 K is measured. Moreover, the experimental results are compared with theoretical results based on master equations and those simulated by the Direct Simulation Monte Carlo (DSMC) method using the Dynamic Molecular Collision (DMC) model. These results are consistent with each other, enabling verification of the experimental results.

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Recently pressure sensitive paint (PSP) has actively developed to measure continuous distribution of the surface pressure. However, the pressure range has been limited above 1 Torr (133.3 Pa) and there is no application to lower pressure range because the pressure sensitivity seems to be not so high in that range. In this study, we apply three types of PSP [two types are composed by organic dye and polymer (luminophore/binder) ; PtOEP/GP 197 and PtTFPP/poly (TMSP), and another one is Bath-Ru adsorbed on anodized aluminum] to the rarefied gas flow mainly lower than 1 Torr and examine those fundamental properties, such as pressure/temperature sensitivity and time response of luminescence and so on, leading to selection of the most suitable PSP among them for the low pressure range. Finally, the pressure distribution of the surface on which a low density supersonic free jet impinges is measured by the PSP.

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A new technique to measure elongational stress of low viscous viscoelastic fluids in transient planar elongational flow is developed. The measurement instrument for this technique consists of two parts, the squeeze flow cell and the birefringence measurement device. The squeeze flow cell consists a set of parallel plates and generates step planar elongational flow on the stagnation line on the center plain of the plates. The birefringence and the orientation angle along the stagnation line in the start-up flow and the relaxation after cessation of the flow are measured. The elongational stress can be calculated from these optical data when the stress-optical rule is applicable. The comparison between the velocity distribution and the birefringence measurement using the flow cell that has several dimensions shows that the elongation rate distribution is not constant along the stagnation line by the sidewall effect. However, it is confirmed that reasonable results can be measured under the flowing condition, W=40 mm, L=20∼40 mm, H₀=36 mm, where W and L denote the width and the length of the parallel plates and H₀ is the initial gap of parallel plates. The surfactant aqueous solution CTAB/NaSal, which is Maxwell fluid at low shear rate, is used as the sample of trial test of this technique. The planar elongational viscosity η_ep of this sample is measured by our technique and it is compared with shear viscosity η. Trouton ratio Tr (=η_ep/η) becomes almost 4 and this result demonstrates ability and practicality of our technique.

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Recently a new transport system "Aerotrain" has been proposed, and test using the first and second stage models are conducted in a 3 km guide way of old MAGLEV test facility in Miyazaki prefecture. "Aerotrain" has wings, and flies close to the ground of an open channel to take advantage of the ground effect. Characteristics of wing in ground effect (WIG) have been investigated using conventional wind tunnels. But this type of experiment cannot estimate the ground effect correctly because of the existence of boundary layer developed between bottom of the wings and the ground surface. Therefore, it is necessary to experiment using a towing wind tunnel to clarify characteristics of wing in the real ground effect. The aerodynamic charactersistis of two kinds of aerofoil sections: NAGA 4412 and circular arc aerofoil were clarified by the experriment towing the aerofoils in 3 km guide way of MAGLEV test facility. In addition, we examined problems to utilize the guide way of old MAGLEV as a towing wind tunnel.

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As a fundamental equipment for studying blood flow in microcirculation, the inclined centrifuge microscope enables us to measure frictional characteristics of cells moving on a plate in a medium under the effect of inclined centrifugal force. Specifically, this paper deals with measurement for red blood cells moving on a glass plate in plasma. First, accuracy of the manual measurement of cell velocity through the microscope was confirmed in comparison with the image processing method. Measurement was then performed confirming frictional characteristics of red blood cells were properly modeled as the sum of the Coulomb friction with friction coefficient of 0.206 and the linear viscous friction applied on a simplified circular disk with a plasma layer of thickness of 0.176 μm in the present condition.

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In the present paper, studies of dragonfly wing revealed the structural morphology and the aerodynamic characteristics. Some experimental studies on dragonfly wings were performed with a scanning electron micrograph, a three-dimensional curved shape measuring system and a Particle Image Velocimetry (PIV) system. Firstly, the scanning electron micrograph observed the cross section shape of a dragonfly wing. Secondly, the system for the measurement of surface shape measured the surface roughness of a dragonfly wing with μm order accuracy. The results of surface shape mesurement revealed there are three regions on a dragonfly wing, which had different function for a wing. Lastly, the PIV system measured the flow characteristics around the dragonfly wing and the flapping dragonfly. The analysis of two-dimensional velocity fields with the PIV system clarified the existence of the large velocity areas over a dragonfly wing and the specific flows around a flapping dragonfly.

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In centrifugal compressor or blower, operation becomes unstable as flow rate reduces because of self-exciting phenomena like rotating stall or surge. This study describes unsteady phenomena in the static pressure field due to rotating stall observed in a radial vaneless diffuser of a centrifugal blower, experimentally. Static pressure measurement was conducted using pressure transducers attached on shroud side wall of the diffuser. The data was acquired slowly changing the operation region from stable to unstable by throttling the flow control valve. As result, by means of continuous FFT analysis, wavelet analysis, and cross-correlation analysis, transient process under unsteady condition in the diffuser was clarified.

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In this paper the relationships between power augmentation of the HAWT due to Mie type tip vane application and other factors influencing the efficiency of a wind turbine such as blade aspect ratio, number of blades, blade pitch angle and Reynolds number are investigated. Experiments have been carried out in a large scale wind tunnel. Rotor models used are respectively 2 and 3 blades wind turbines and 4 sets of blades with different aspect ratio have been experimented. For an existing rotor without Mie vane, a maximum power augmentation about 14.5%, due to Mie vane application, is achieved. The relationships between power augmentation by Mie vane and the above factors are investigated. It is found that the application of Mie vane is more efficient in case of rotors with small aspect ratio and for low wind speeds. Surface oil-film and surface tuft visualization methods are used to detect the flow patterns at the blade tip. Attaching Mie vane, improved flow around blade tip is evidenced.

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The authors have proposed, in the previous report, the counter-rotational type machine for the hydroelectric power generation. Continuously, the hydraulic performance of the counter-rotating runners is discussed in this report. The variable speed/head and the discharge characteristics satisfy the similarity laws, and the rotational speed of the individual runner increases respectively in proportion to the discharge that can be predicted theoretically under the counter-balanced condition of the angular momentum change through the runners. These behaviors cause that the operating point with the maximum efficiency is at slower speed or smaller discharge than one with the maximum output. The potential interference between the front and the rear runners is also discussed with the numerical results of the quasi-three dimensional flow analysis.

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Combined nongray radiative and conductive heat transfer in multiple glazing subjected to solar irradiation is analyzed. A spectral solar model proposed by Bird et al. is used to calculate direct and diffuse solar irradiance. The radiation element method by ray emission model, REM₂, is used to analyze spectral radiative heat transfer. Specular reflection at boundary surfaces is taken into account. Spectral dependence of radiation properties of glass such as specular reflectivity, refraction angle, and absorption coefficient is taken into account. Steady-state temperature and heat flux distributions in glass layer are obtained and insulating efficiency of multiple glazing is examined. Overall heat transfer coefficients predicted by the present method are compared with those based on the JIS method. The values obtained by the present method are slightly smaller than those obtained by the JIS method. To investigate the spectral variation of radiative heat flux attenuated during glass layer, spectral heat flux at room side surface and incident radiation are compared.

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Fluidized bed combustion is one of advantageous technologies for coal and/or incineration firing especially with respect to the environmental protection of emissions, such as NOx/SOx. Bed material movement in such fluidized bed has a prime importance in the heat transfer process. Thus the quantitative measurements of bed material movement and void fraction are indispensable for better understanding fluidized-bed. In this investigation, neutron radiography is applied to visualize the bed material movement in a simulated fluidized bed heat exchanger installed with vertical tubes. Bubble behavior and void fraction profile are obtained by using the image processing technique. Bubble movement is highly restrained by these vertical tubes to that the bubbles rise up along the tube. The bubble diameter is well correlated by modified Mori&Wen's correlation taking into account the pitch of tube arrangement. The bubble rise velocity and void fraction are well correlated by applying the drift-flux model.

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The longitudinal heat transfer in capillary pipes is enhanced by fluid oscillation. The analytical solution to this phenomenon is obtained considering the wall thermal conductivities. Based on this solution, the effects of wall conductivity and thickness are investigated for the case of large amplitude of fluid motion. The longitudinal heat transfer through the fluid part is more enhanced with highly conductive thick pipes. This is because the radial region where the heat is transferred backward is smaller with these pipes. The direction of longitudinal heat transfer depends on the phase difference of temporal change between the velocity and temperature; whether it exceeds π/2, or not. From this point of view, the most effective wall to this problem is presented, where the wall temperature does not change preserving the mean temperature of the location during the oscillation.

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Effective utilization of natural energy by an Aquifer Thermal Energy Storage system has been a continuing research theme of our laboratory for 20 years. By start-up the heat storage performance was low, but it has been gradually rising throughout the years and has now apparently stabilized itself at a high value. The reason of the improved heat storage performance is that charge and back washing was repeated in the well. As the result, ferric colloid formed a dam around the well, and the ground water flow was cut off. The present paper determines the necessary pressure gradient for destroying the ferric colloid by back washing. Experimental verification is carried out by using a one-dimensional test equipment.

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An auto-ignition process in a premixed charge compression ignition engine was numerically solved by the Very Large Eddy Simulation (VLES) in conjunction with a reduced kinetic model for the low temperature oxidation of a hydrocarbon fuel. A new method was employed to set the initial turbulent velocity field, adjusting the velocity field so that the dissipation process may fit the results of the K-ε model. The phase averaged quantites of the VLES agreed well with those of the K-εmodel. The VLES exhibited the spatially random appearance of auto-ignition sites, which is similar to experimental observations shown in the literature.

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In order to clarify the ignition mechanism of fuel sprays, an ignition model was developed employing the stochastic turbulent mixing model and a reduced chemical kinetics. Using this model, the time histories of heterogeneity in temperature and equivalence ratio of mixtures were analyzed. At low initial surrounding air temperatures, exothermic reactions start in mixtures having equivalence ratios in a very narrow range. On the other hand, at higher air temperatures mixtures with variety of equivalence ratios ignite. This phenomenon can be explained by dependency of mixture reactivity on the equivalence ratio and the temperature. Based on the results, discussion was made on the similarity and difference in temperature dependency of ignition delays between sprays and homogeneous mixtures.

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In the actual spray combustion fields, coupled combustion process should be occurred, between the pre-evaporate fuel component and remaining liquid droplets. Therefore it is insufficient to clarify the fundamental spray combustion mechanism with use of only droplet or only premixed mixture analyze method. In this study, the premixed mixture-droplets coupled combustion field was focused, as a model of the actual spray combustion field. In the experiments, the effect of the flame pattern and the burning rate constant by the interference between the droplets were clarified with the variation of droplets fuel. Besides, effect of the premixed gas surrounding the droplets was clarified by the experiment on coupled combustion. The experiments were carried out under the normal gravity field and the microgravity field to estimate the effect of convection in combustion field.

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The object of this study is to reduce nitrogen oxide using a DC corona discharge. The mixture of (N₂+O₂+NO) was used as the sample gas. After the mixture was passed through the reactor in which corona discharge field was formed, the gas collected at the exit of the reactor using a sampling bag. The components such as NO, NO₂ and N₂O etc. were analyzed with FT-IR and NOx meter. It was found that the characteristics of NO reduction by corona discharge differed remarkably whether or not the oxygen was existing in the mixture. From the measurement of spectrum of light emission by corona discharge in N₂ or (N₂+O₂) atmospheres, several N₂ bands were detected. In the case of N₂ atmoshere, the process of NO reduction was mainly controlled by N₂ radical produced in the corona discharge field. On the other hand, in the case of (N₂+O₂) atmosphere, NO converted to NO₂ by ozone which yielded by corona discharge.

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Developing a low NOx gas turbine combustor, usually requires many experiments on flow and combustion. Computational prediction technology in the combustion field has progressed with advances in the computer technology and the turbulent combustion model. This report covers applications of CFD for the development of the gas turbine combustor and some discrepancies between CFD and experimental results, and improved methods to solve them.

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