In the present paper, a new method that is called HGA (Hybrid Grid Adaptation) Method is reported. It is very important to generate grids easily around complex objects in recent numerical simulations, in order to use limited computer resources efficiently. In the present paper, the kinds of grid, which have great effect on analysis accuracy and efficiency, are paid attention to. In three-dimensional problems, only Tetrahedron and Hexahedron is usually used. The former, which has an advantage of flexibility, can be applied to complex objects better than the latter. The latter can analyze flow problems more efficiently than the former. Prism, which has flexibility and efficiency, and Pyramid is used. So we used Hybrid Grid (Tetrahedron/Pyramid/Prism/Hexahedron) to take the advantage of both flexibility and efficiency. And we tried to analyze them more efficiently, using HGA Method included AGR (Adaptive Grid Refinement) Method, which obtains higher resolutions by collecting fine grids only in the location where the change of the physical quantity is intense, based on Hybrid Grid.

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It is important for a fire suppression system to keep the target concentration in all regions of a protected room. In this study, the effects of aspect ratio of the protected region, position and area of the pressure relief port, area of an obstacle in the protected region and the number of nozzles on the mixing process of gaseous suppressant are investigated by large eddy simulation. Besides, the evaluation method of the mixing condition is discussed. The results show that the gaseous suppressant is insufficiently mixed when the aspect ratio of the protected region is large and that the mixing condition can be evaluated by the ratio of the target concentration attainment.

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An experimental study on droplet generation for the rapid detection of cells by using cell sorters was conducted. Cell sorters create micro-droplets by controlling waves at surface of a micro-jet which consists of samples and sheath fluid. In this paper the optimum wave number was observed by microscope. The ratio of sample flow rates to sheath flow rates and frequency of the wave are also controlled in order to investigate those effects on droplet generation. In addition to the experimental studies linear instability analysis for droplet generation and numerical simulations for the flow distribution in the chamber of the cell sorter were carried out to obtain optimum parameters to maximize the rate of droplet generation. Analytical solutions agree well with the experimental results of droplet generation.

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This paper is focused on the conditional averaged characteristics of mean velocity of longitudinal vortices downstream of an active vortex generators pair (AVG) with common-flow up configuration (CFUC). An active control of turbulent boundary layer and/or separation is one of the most challenging projects. It is important to achieve an effective control system based on the information of flow characteristics. Therefore, it is a challenging research to understand the transitional behavior of longitudinal vortices submerged in the turbulent boundary layer. The streamwise vorticity shows more rapid response to the height of the AVG at up-phase compared with at down-phase. The transportation of high velocity fluid beneath the longitudinal vortices plays an important roll on the response of longitudinal vortices to the hight of AVG.

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The behavior of the boundary layer in rotating channels, such as that in impeller passages of turbomachinery, is dominantly influenced by the centrifugal and Coriolis forces due to the wall curvature and system rotation, respectively. The resultant force may promote or suppress the instability in the boundary layer, depending on its magnitude of the component normal to the wall boundary. The purpose of the present study is to make clear experimentally the effects of Gortler type instability on the laminar boundary layer developing along the concave surface, focusing attention on transition process from laminar to turbulent state in the rotating system with streamline curvature. The longitudinal velocity and turbulent intensity have been measured near the concave surface in the channel whose radii of center line curvature is 1000 mm. When the Coriolis force acts toward the concave wall due to the channel rotation, the occurrence of the Gortler vortices shifts upstream and the vortex structure is maintained in more downstream sections. In the earlier stage of vortex development an oscillation of flow was found to appear in the vortices irrespective of the rotating condition.

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In this study we examine the applicability of the Mini Doppler Sodar as an instrument evaluating wind characteristics for constructing a wind farm. The data obtained from the Mini Doppler Sodar were compared with those of the 70 m observation tower at Hoiyo Sand Dune, where is known to be windy and to be expected constructing a wind farm. The Mini Doppler Sodar gave the wind speed and direction almost the same with those by the tower at each height. When land breeze blew, the Mini Doppler Sodar data agreed with the Tower data, but disagreed at the other times, because of sound noises and turbulence in a convective boundary layer. The data are however able to be compensated by using a regression line. The Mini Doppler Sodar will be suitable for the assessment of wind characteristics after some improvements.

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The in-line vibrations of an elastically supported circular cylinder subjected to cross flow were experimentally investigated, where velocity fluctuations in the cylinder wake were measured by two probes of a hot-wire anemometer symmetrically set up. Typical in-line vibrations were observed in two flow velocity ranges, one in the reduced flow velocity of 1.3-2.5, and the other in 2.5-3.5. In higher velocity range, out-of-phase velocity fluctuations were measured, which shows alternative vortex-shedding. In lower velocity range, in-phase velocity fluctuations were observed, which shows symmetrical vortex-shedding. Flow visualization confirmed the periodical formation and shedding of symmetrical vortices. It is concluded that the in-line vibration in low flow range is a kind of hard self-excited vibrations due to the interaction between the cylinder vibration and the symmetric vortex formation by the cylinder vibration itself.

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A mathematical model discribing the acoustical characteristics of a bubble cloud containing N bubbles is derived taking bubble interaction effects into account. The method of multipole expansion, by using both singular perturbation method and the matching procedure, is carried out to determine the coefficients of the spherical harmonics expansion to satisfy boundary conditions of both on the bubble surfaces and at the infinity. Discrete characteristic equations are obtained from a set of N algebraic equations, under the assumption of potential flow and spherical bubble shape of bubbles.

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A miniature vibrating hollow-fiber filtration device, in which a hollow-fiber cartridge mounted on a bridge held by two plate springs is vibrated to axial direction by a vibration motor, has been developed. The device can restrain the deposition of particles on the membrane surface by the vibration. A device, which has two hollow-fiber (length of 190 mm, an inside diameter of 1 mm and pore diameter of 0.1 μm), was tested at a membrane vibration frequency of 40 Hz and an amplitude of 2.5 mm p-p. During the test the liquid (Kaolin suspension ; turbridity : 1000) was filtered through the membrane for two weeks. It was found that the rate of permeation is almost constant after the test. However, when it was not vibrated, the end permeation rate was one quarter of the rate when vibrated.

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A MEMS-based micro mixer is developed to be integrated into a bio-molecule sorting system, in which efficient mixing of magnetic beads with target bio-molecules is crucial. The mixer consists of embedded micro-conductors, which produce a time-dependent magnetic field, and a micro channel, which guides the streams of working fluid and suspension. It is demonstrated that integrated 2-D micro conductors provide a magnetic field strong enough to attract nearby magnetic beads. Numerical simulation helps to design the arrangement of channel and embedded electrodes that can generate chaotic motion of beads. It is found that the serpentine channel geometry with the transverse electrodes is able to create the stretching and folding of material lines, which lead to chaotic mixing. Similar mixing pattern is confirmed experimentally in the chaotic mixer fabricated. The fast mixing thus achieved facilitates the attachment of beads onto the target bio-molecules.

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A direct numerical simulation (DNS) based on a finite volume method is applied to a particle-laden turbulent mixing layer in order to examine effects of loaded particles on turbulence and scalar diffusion. Trajectories of all particles are individually pursued with a Lagrangian method. The results show that the small particles, whose response time, τ_p, is smaller than the Kolmogorov time scale, τ_k, reduce the turbulent intensities of streamwise and transverse velocity fluctuations upstream of the mixing layer. However, the streamwise slope of turbulent intensities becomes high as compared to particle-free flow downstream of the mixing layer. Because source terms, which are energy exchange and turbulent production terms for the turbulent intensity of streamwise velocity fluctuation and pressure strain correlation term for that of transverse velocity fluctuation, are increased. Furthermore, the small particles increase the mean squared values of the concentration fluctuations.

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Experiments have been performed for a turbulent channel flow obstructed with a flat body. Thickness of the body is 5 mm and 10 mm, and the clearance between the wall and the body is changed in three steps. The local heat transfer coefficient, wall static pressure and wall shear stress are measured. A split hot film probe is used for the measurements of velocity profiles and turbulent intensities. When the clearance is large, the vortex shedding is observed, however the vortex shedding disappears at the small clearance. Enhancement of the heat transfer coefficient at the small chearance relates to the increase of turbulent kinetic energy in the vicinity of the wall. On the other hand, at large clearance it relates to the increase of the streamwise velocity near the wall.

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Finite difference solutions to the Leslie-Ericksen equations for nematic liquid crystals are obtained for two-dimensional flow between parallel plates under a magnetic field imposed on a part of the flow domain with a transverse component. The flow is symmetric with respect to the channel centerline at small Zocher numbers, while the director aligns with the magnetic field and the flow symmetry is broken when the Zocher number becomes more than a critical value. This value at which a Freedericksz-like transition in director orientation is induced increases with increasing Ericksen numbers. After the transition, streamlines show a wavy pattern in the magnetic field, and vortices occur at the channel walls. The velocity profile is flat in the field, because imposition of the field induces a transverse alignment of the director near the channel centerline, resulting in a higher viscosity there and a lower viscosity near the channel walls. Furthermore, we have simulated the flow with a magnetic field imposed on the whole flow domain, and it is found that the finite extent of the magnetic field acts to retard the transition.

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A scalar probability density function (PDF) approach considering a detailed chemical kinetics is applied to a diluted hydrogen jet diffusion flame to evaluate the performance. The flame is formed on the nozzle of an inner diameter of 6 mm, with a fuel exit velocity of 30 m/s, surrounded by two annular pipes issuing airs of higher and lower velocities of 30 m/s and 3 m/s, respectively. The flow field has been solved on the basis of the k-ε two equation model. The modeled PDF transport equation has been solved by an Eulerian Monte-Carlo method. The results are compared with those of two flamelet calculations, which are based on the conventional laminar flamelet model method and a scalar PDF method based on the conserved scalar approach. The present PDF method predicts the maximum temperature on the center axis close to the experimental one than the other methods. The temperature downstream of the maximum temperature position has however been overestimated due to the underestimate of the mixing. The present PDF method has reproduced the extinction and reignition phenomena, which cannot be easily predicted by the conventional flamelet calculation. The variation in the diffusion flame structure due to the flame stretch, which was experimentally confirmed by Barlow et al., has been also reproduced. Moreover, the PDF calculation has revealed that intermediate radical species are created largely under the flame stretch effect.

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The heat transfer is enhanced in curved pipes by the secondary flow. Its stirring effect is expected to be more augmented in multiple pipe bends which form a coiled pipe with periodically canging the plane of curvature. Numerical investigations of flow and temperature field including the developing region in such a pipe are carried out in laminar flow regime using parabolized governing equations. The calculation method has been validated for coiled pipes. In multiple pipe bends, Coriolis force due to the change of curvature plane causes complicated secondary flow pattern, realizing more homogeneous mixing. In the case of high Prandtl number fluids, the heat transfer is more enhanced in multiple pipe bends compared with in ordinary coiled pipes. Meanwhile, this is not the case for low Prandtl number fluids. The mechanism which causes this opposite effect is also discussed.

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In recent years the requirement for reduction of energy consumption have been increasing to solve the problems of the global warming and the short of petroleum resources. For example in the power generation field, as the thermal power generation occupied 60% of the power generation demand, the improvement of the thermal efficiency is required considerably. This paper described that the pressure drop characteristics of the finned tube banks used for the heat exchanger in the thermal power generation were clarified by testing the serrated finned tubes banks for improvement of higher heat transfer and the conventional spiral finned tube banks under the same test conditions, and that the equations to predict pressure drop coefficient which is necessary to design the heat exchanger were proposed.

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The flow field of a three-dimensional, time-dependent thermal plume in stably stratified ambient above a heated square plate was elucidated by solving numerically governing equations. Phenomena characterizing this plume are as follows : (a) Velocity vectors on a horizontal plane above the heated plate have a X-shape distribution at any stratification. (b) The local Nusselt number distribution on the plate was affected by the X-shape distribution. (c) In Velocity vectors on the vertical plane, a V-shape occurred near the plate, and a horizontal imterface occurred between inward and outward flows. Time-dependency in the plume is resulted from instability near the front with negative buoyancy, and became weak with increasing stratification. At the extremely strong stratification, flow became steady state. The flow at strong stratification differed clearly from that at medium stratification as follows : At the medium stratification, the upward flow interfered with the stratified air, and a Π-shape of the velocity vector distribution occurred near the front. However, at strong stratification, the stratification effect is more dominant than the upward flow effect, and a Λ-shape occurred. With increasing stratification, the flow velocity near the plate became small, and the mean Nusselt number decreased.

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Combustion in standing sound wave induces a new type of convection that is named as thermo-acoustic streaming. The mechanism of the streaming is analyzed and experimental investigations are made to evaluate its influence on burning rate of a droplet. Since natural convection has characteristics very similar to the streaming, microgravity conditions were used to suppress it. Burning rates are measured for an accoustic frequency of 900 Hz and SPL of up to 150 dB under ambient pressure of 0.1 to 0.5 Mpa. As a result, the excess burning rate (k/k₀-1) is confirmed to be proportional to Gr_a^0.25 or Gr_a^0.5, where Gr_a is the ratio of acoustic radiation force to viscosity. The hypothesis that the streaming is driven by acoustic radiation force is validated and burning enhancement is explained through enhanced convective transfer due to the streaming.

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This paper presents results of an experimental investigation on the combustion of a single droplet in the vicinity of a cold wall in microgravity. The fuel was n-heptane, and the ambient gas was air at normal atmospheric pressure. Two types of plates with different reflectivities were used as the cold wall. Droplet burning lifetimes, burning-rate constants, durations of the initial heat-up period and several flame characteristic scales are presented and discussed. The results showed that the wall causes flame deformation and flame extinction when it is close enough to the droplet. The droplet-burning lifetime reaches a minimum at a certain spacing between the droplet and the wall surface. This combustion enhancement is principally seen as a reduction of the initial heat-up period. It is suggested that the reduction of the total burning time is due to enhanced conductive heat transfer to the droplet caused by flame deformation. The present configuration is similar to that of combustion of a droplet pair. Comparisons with results for droplet-pair combustion are also presented. From the comparisons, several similarities were found, but the mechanism appears to be different. These differences are also discussed in the paper.

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This study is focused to propose the new spray-wall interaction model for application of direct injection engine systems. In this paper, the experimental approaches are discussed for two kinds of droplet-spray regime. As the 1st step, small non-dispersed droplets or droplet array impinge on the heated flat wall with the variation of droplet Weber number, impingement angle and wall temperature. In the 2nd step, actual spray through the gasoline injector for D.I.S.I. Is impinged on the flat wall. Here, droplet behavior on the wall and post impingement properties are measured by high-speed photographic systems. Then, the new submodel is constructed based on droplets experimental results. This new model is incrporated into KIVA-3 code. And the results calculated by this model are compared with experimental results. It was found that the results by this model for the spray dispersion near the wall were consistent well with the actual process over all boiling state conditions.

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Fuel temperature in the injector of direct injection gasoline engine is high. On some conditions it exceeds over 410 K. In order to understand spray behavior and mixture processes on these conditions, the effects of fuel temperature on spray characteristics injected by a swirl type injector for direct injection gasoline engines were investigated; In experiments, a constant volume chamber is used to visualize spray and mixture formation processes by LASER sheet, shadow graph and schlieren techniques. In addition Sauter mean radius (SMR) were measured. As these results, increasing fuel temperature over saturated temperature roll up didn't exist, the spray width was narrow and the penetration length was extremely long. Moreover although evaporation occurred quickly, the fuel vapor mixed with the surrounding air incompletely. This is because spray gathered near the nozzle axis and roll up didn't exist.

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Prediction of knocking occurrence was examined in order to quantify knocking phenomena and evaluate combustion systems in pre-chamber lean burn gas engine. By the temperature two region combustion model and thermodynamics diagnostics the temperature of end gas was calculated. Empirical relations of instantaneous temperature and pressure of end gas for induction time was conducted by experiment of single cylinder engine. The single cylinder engine has a bore of 165 mm, a stroke of 185 mm and pre-chamber system with compression ratio of 13.2. Prediction of knocking occurrence was examined by Livengood-Wu integral. It was found that the temperature two region model could express combustion of pre-chamber gas engine and could evaluate combustion systems in pre-chamber lean burn gas engine.

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The regulation for the automotive diesel engine emission becomes severe every year, and more effective post-processing technology is desired especially on particulate matter (PM), such as carbon soots. Although the use of ceramic diesel particulate filter (DPF) is now a leading technology for PM removal, the problem exists on the soot incineration or regeneration at low temperature, especially at the cold start. In the present study, a regeneration of DPF was investigated using the low temperature atmospheric pressure nonthermal plasma. The method is to use the NO₂ and radicals induced by the plasma reactor to burn carbon soots deposited on DPF. First, three types of DPF plasma reactors were constructed and the performance on the conversion of NO to NO₂ was evaluated on various conditions. Regeneration experiment was further carried out using a DPF honeycomb nonthermal plasma reactor. As a result, it was confirmed that the pressure drop decreased only when the plasma was turned on and the regeneration temperature of DPF was less than 200°C.

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Chemically recuperated gas turbine (CRGT) is an advanced cycle, which recovers exhaust heat by endothermic reaction converting fuel into hydrogen-rich gas. CRGT can improve the generating efficiency of the simple cycle GT more effectivly than the stream injected GT cycle does. In our 1st report, we made clear required specifications of the reformer in the CRGT system with natural gas steam reforming and designed a reformer consisted of tube bank by numerical analysis considering mass and heat transportation and chemical reactions. On the next stage, we examined the designed reformer experimentally using a test module. We also examined combustivility and emissions of the low-BTU gas containing much steam in the combustion test. It was comfirmed that the reformer design was valid and heat recovery was evaluated accurately. Also, combustivility of the reforming gas was apploximately steady and the NO_x emission was under 10 ppm.

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There are many types of fire barrier materials. Among them, a fire barrier material which intumesces at low temperature is made of a rubber in which intumescent materials are mixed. Sodium silicate is one of the intumescent materials. In this report, the thermal intumescent characteristics of sodium meta-silicate are investigated. Thermal intumescent ratio of sodium meta-silicate were measured using a thermo-gravimetry (TG/DTA) with the heating rate in the range from 1 K/min to 99.9 K/min. As the result, it is clarified that thermal intumescent characteristics depend on the heating rate. Thermal intumescent ratio increases with increasing the heating rate. Intumescence was observed when the heating rate was 40 K/min or faster. The intumescence has been almost completed at 443 K.

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