We have investigated aggregate structures of a colloidal dispersion composed of ferromagnetic plate-like particles with a magnetic moment normal to the particle axis at the particle center, by means of three-dimensional Monte Carlo simulations. For no applied magnetic field cases, long cookie-like clusters are formed as magnetic particle-particle interactions increase. Characteristics of these clusters are that particles incline in a certain direction and their magnetic moments alternate in direction between neighboring particles. For applied magnetic field cases, the particles incline in the magnetic field direction so that the cookie-like clusters are not formed easily. When the magnetic field has the same order of influence as the magnetic particle-particle interactions, the particles do not form the clusters. However, as the influence of the magnetic field and magnetic particle-particle interactions become significantly strong, thick chain-like clusters are formed along the magnetic field direction.

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We have conducted the basic study on the lattice Boltzmann method from the viewpoint of applying it to many particle suspensions, by considering a uniform flow past a two-dimensional circular particle (i.e., cylinder). Successful application of the lattice Boltzmann method to particle dispersions is strongly dependent on what rough lattice system can be used, since the motion of suspended particles and the flow field have to be solved simultaneously, unless a rough lattice system is used, suspensions with sufficient number of particles cannot be treated in simulations. Even if a significantly rough lattice system with the lattice unit width of one-fifth times as long as the particle diameter is used, the results give rise to physically reasonable agreement with the Navier-Stokes solutions.

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We have investigated aggregate structures and rheological properties of a colloidal dispersion composed of ferromagnetic spherocylinder particles with a magnetic moment along the particle axis direction, by means of Brownian dynamics simulations. In concrete, we have attempted to clarify the influences of the flow field, magnetic field strength, magnetic interactions between particles and volumetric fraction of particles. For the case of a strong magnetic field and strong magnetic interactions between particles, wall-like clusters are formed along the magnetic field direction. As the influence of the flow field increases from such a situation, those clusters dissociate, and the particles are tilted to the flow direction.

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This paper describes elucidation of propulsion mechanism of white blood cell with driving force by concentration gradient using computational model. In our previous experiments, it was found that the white blood cells move when the concentration gradient on the membrane is opposite to the concentration gradient of surrounding fluid. To investigate these phenomena by computational model, transport process of concentration near the cylinder with consideration of absorption factor and diffusion coefficient ratio. It is concluded that the opposite gradient can be generated when the proper diffusion coefficient ratio and absorption factor.

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We present numerical tests of outflow boundary conditions at an open boundary for simulations of vortex flows. The Sommerfeld radiation condition is convenient for finite difference methods and often used. However it is not clear which value of the convective velocity is appropriate. We compare four different convective velocities, which are mean velocity at exit boundary, arithmetic mean velocity of maximum and minimum value at exit boundary, local instantaneous velocity, and calculated velocity from Orlanski's formulation. The test cases for boundary conditions evaluation are double Lamb dipole vortices convecting in week uniform flow, and a two-dimensional jet flow. The Orlanski's method yield little reflection and is recommended for use at open boundary.

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The deep-sea drilling vessel "CHIKYU" is a riser-equipped, dynamically positioned scientific drill ship owned and operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and built for the purpose of scientific research and exploratory expeditions. Recently, measurement while drilling (MWD) technology can transmit real-time data from the downhole to the upper surface of the vessel using a pressure wave, i.e., mud pulse, generated with a pressure modulator through the drill string. In this study, a numerical one-dimensional fluid model has been designed and analysis carried out under the assumption of a pressure modulator located within the drill pipe to monitor mud pulse simulations.

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Femtosecond pulse laser (fs pulse) is high intensity and ultra-short pulse laser. It easily induces nonlinear optical phenomena for various materials. In this study, we carried out the time-resolved measurement in order to investigate the process of bubble nucleation induced by femtosecond laser irradiated into pure water in detail. In the time-resolved measurement, the pump-probe method and high-speed video camera was applied. From the results of time-resolved measurements, in about 800 ps, intensive lights were emitted from the central portion of the region in which the refractive index of the water was changed by the fs pulses. Subsequently, bubbles were generated at about 1 ns after the fs pulses irradiation into the water.

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The growth and collapse of a bubble under a floating body are simulated by using the boundary element method to predict the damage of ship bodies induced by underwater explosion. The three-dimensional deformation of the bubble, the translation and rotation of the floating body, and the motion of water surface are taken into account in the simulation. It is shown that the Kelvin impulse is found to be useful in predicting the translational motion of the bubble. Also, the horizontal translational motion of the bubble is much dependent on the rotational motion of a floating body; when the moment of inertia of the floating body is small, the largest horizontal translation is realized between the axis of flotation and the edge of the floating body.

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The homogenizer basically consists of a high-pressure plunger pump usually with triple plungers to minimize pressure fluctuations and a homogenizing valve with a narrow gap. However, the flow within the homogenizing disk part is not clarified theoretically. If the flow pattern within the disk part could be solved, a more efficient and stabilized emulsification could be carried out. The flow patterns were investigated using a CFD model of the flow in the disk part. In this paper, the influence of shape modification of the disk part was investigated in the droplet break-up action. Moreover, the influence of droplet break-up action was investigated by using two kinds of liquids.

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Experimental and numerical study on liquid jet occurrence in converging tubes is conducted, in order to clarify the detailed mechanism of the jet occurrence and bubble breakup phenomena. It is found experimentally that the liquid jet is observed in the converging tubes without divergent section, which indicates the divergent part has no contribution to the jet occurrence. It is also shown that the ratio between bubble diameter and tube diameter is more important for the jet velocity than the bubble diameter. Numerical results, which are confirmed to agree well with experimental results, show that the jet is caused by the steep gradient of a static pressure behind the bubble. The steep pressure gradient is locally and impulsively generated by the concentration of pressure difference and the convergence of flow behind the bubble.

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A separation device using swirling flow has been investigated and made practicable. In the present study, our subject is to develop a separation system of multiphase flow with solid and liquid. Especially, the technique for the separation and collecting the particle such as the cutting dwarf and oil in the processing waste fluid is one of important problems. Micro-bubbles, on the other hand, are used for the environmental improvement and washing. Micro-bubbles are used for elimination of oil and the solid particulates from waste fluid by the centrifuge in the present study. The behavior of solid particles and micro-bubbles in the swirling flow are observed as the first step of development in a solid-liquid separation system.

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High-speed two-phase flow is very important in developing the ejector for refrigeration system and in the total-flow system of a geothermal power plant. At the mixing section of the two-phase flow ejector, the supersonic driving flow mixes with the subsonic suction flow which generates shock and expansion fans. This study focuses on the characteristic of the two-phase flow in which the phase-change occurs. The expansion fans were calculated using the CIP method. When the equilibrium mach number is larger than 1, the centered expansion fan is calculated in supersonic mist flow with small relaxation time. On the other hands, the start point of expansion fan is move to upstream, and the convex shape of expansion fan is appeared for larger relaxation time. We found out that the different type of expansion fans according to the speed of the phase-change.

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This paper presents a performance evaluation of phase-shifting digital holographic method for fibrous object in 3D space. The performance is evaluated in number of detected fibrous objects in comparison with that of the method without a phase-shifting technique. Fibrous objects are represented by the candidate points detected in a reconstructed volume, and then the candidate points are clustered with self-organization algorithm to separately recognize each fibrous object. In numerical simulation, it is found that the accuracy of the present method in fibrous object detection is better than that of conventional inline digital holographic method.

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Integral photography (IP) is a technique to record a three-dimensional image on a photographic plate with a single-camera. In this paper, digital IP is applied to three-dimensional PTV. By using digital IP, three-dimensional positions of tracer particles can be measured easily on a computer from a single captured image. The performance of the present three-dimensional PTV is evaluated in numerical simulation and experiment. In numerical simulation, the measurement accuracy is examined with a digital IP in particle depth position that is measured in a set of reconstructed images. In experiment, flow velocity is measured in a circular tube by using the present PTV based on digital IP.

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The target of this study is to demonstrate the mixing ability of an alternate pumping microreactor. We adopt visualization of the dilution of methylene blue solution with water in microreactors. The captured image presents the distribution of the brightness in the channel. According to the relation between the concentration of methylene blue and the brightness, the obtained brightness distribution gives the concentration field in the channel. The obtained concentration fields in the alternate pumping microreactor and an ordinary microreactor illustrate that the mixing region spreads in the whole area of the channel in the alternate pumping reactor and the mixing region area in the ordinary reactor is limited in the narrow area at the channel center.

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Recently, the study on the flow around a wing at low Reynolds number has been carried out actively. It was also desired to measure the minute pressure on the wing surface with good accuracy. However, the commercial sensors were not suitable for the small pressure and their sizes were too large to put them on the wing surface. Thus, we devised the manufacturing process of a semiconductor-type sensor for the pressure measurement within the range of several Pa using MEMS (Micro Electro Mechanical Systems) technology. Furthermore, we evaluated the output characteristics of the sensor.

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One problem on the 24 hours house ventilation system is trouble with maintenance of dirt air filter. The axial flow cyclone air intake hood was developed in order to reduce filter maintenance cost. However, the optimum design parameters of this cyclone intake hood have not been obtained yet, especially the relationship between performance for a cyclone dust collector and internal flow in an intake hood are unknown. The purpose of this investigation is to make clear the relationship between performance and internal flow. As the result of this study, velocity and pressure distributions in intake hood were shown, and we examined the relationship between performance for a cyclone dust collector and these results.

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The viscous pump, which has a rotor with helical rectangular channels, is studied experimentally. Eight types of torsion of the channel are made to investigate the torsion effect on the flow characteristics. We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump. We also observe the secondary flow at a cross-section of the channel. Some of the results obtained are shown as follows: The pressure gradient along the channel to get the same flux is large for large channel torsion at a constant rotation, and becomes small when the favorable rotation of the rotor to the flow is applied. As for the secondary flow at a cross-section, there appear several types of vortex. When there is no rotation, the secondary flow is almost symmetric two-vortex type for small flux as is the ordinary Dean vortex, but it changes to a four-vortex type when the flux is large. The secondary flow becomes asymmetric as the rotation increases. We have unsteady flow patterns at large flux and rotation.

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The flow characteristics of synthetic jet near a plane boundary were investigated by conducting experiment and numerical simulation. The flow characteristics with Coanda effect was clarified by comparison the difference of the flow pattern and time-averaged velocity field between formed free jet and near plane boundary. In addition, the flow structure between the synthetic jet and the continuous jet was compared.

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Experimental and numerical analyses were carried out for the turbulent channel flow in 90° T-junction with sharp and various shape corners. The investigations were conducted for flow rate ratios of 0.2, 0.4, 0.6 and 0.8 (ratios between the flow rates in the branch and main channels) keeping the Reynolds number at 4.0×10^4. The results showed that rounding corner reduces the energy loss in the branching flow. The reduction was related to the flow separation at the upstream corner. Whereas the energy loss in the main flow remained unaffected.

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Experiments have been performed for a turbulent channel flow obstructed with an airfoil type turbulence promoter. The clearance between the wall and airfoil is changed in three steps. The total performance evaluation between heat transfer and pressure drop was estimated under the conditions of an equal pumping power. PIV is used for the measurements of velocity profiles and turbulent intensity. When the clearance is small, the heat transfer coefficient is augmented by the reverse flow in the near-wall region and the increase of turbulence intensity.

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In CFD analysis, it is difficult to predict correctly the lift force of a vehicle in high Reynolds number (Reynolds number=1×10^6) which is correspond to actual run condition. In this study, the numerical analysis and the experiment using wind tunnel were performed, and the numerical and experimental results of lift forces were compared. As a vehicle model, the rectangular vehicle models with round leading edge at the front end were used. It was clarified that LES (Large Eddy Simulation) with DSM (Dynamic Smagorinsky Model) was effective for improvement of accuracy, and it was found that the optimal mesh size in the neighborhood of round leading edge surface was required.

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In order to investigate runnning effects of aerodynamic characteristics of a railway vehicle under strong cross winds, we perfomed LES of flow around a simple train model. Numerical results show the slightly difference in the side forces between the running train and the stationary train due to flow separation on the head of the train.

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The pressure measurement has been made on surface of a cone placed in a thin turbulent boundary layer. The apex angle 2α of cone is less than 90° and the height is 50mm. The Reynolds number based on the height is 2.31×10^4 and the relative boundary layer thickness is 0.42. The pressure distribution at θ=0° (θ=0° is the upstream position at symmetric plane.) is strongly depends on 2α. The maximum value at θ=0° can be represented with squared-cosine function of α. When 2α increases, it is expected that a branch flow at θ=0° occurs toward the bottom and top of the cone.

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Numerical solving of fluid-structure interaction (FSI) problems are of importance in various scientific fields. In particular, the establishment of stable numerical scheme is needed in order to analyze the details of flow phenomena. In the present paper, we propose a weak-coupling method for FSI problem: for the large deformable object the rigorous equations of motion are descritized with finite volume method; in the flow computation, the large deformable object is reproduced via immersed boundary method. To demonstrate the performance of proposed scheme, the 3D FSI problem for a large deformable object are solved. The results indicate that the computation is stably conducted using our method,in spite of the occurence of fairly large deformation of the object.

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The fluid-structre interaction problems is important not only for the mechanical engineering problems like a flutter of an airfoil but also for the bioengineering problems like the blood flow in a blood vessel. For the flow analysis at the high Reynolds number of these problems, the method, the object can move freely in the fixed grid, highly affects the precision of the fluid analysis and elastic analysis by having the low resolution of the boundary layer. Therefore, we propose the boundary fitted fluid-structure interaction method and apply to analyze the flow around an oscillating elastic foil. As a result, it is possible to obtain the stable solution of the fluid analysis and elastic analysis. And It is clear about the characteristics of the unsteady fluid dynamics for the flow around the oscillating elastic foil.

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In the design process of aircraft, surface flow visualization is typically required to know separation pattern on a wing and other control surfaces in order to increase lift coefficient, lift-drag ration and stall angle of attack. Therefore, seemingly classic techniques have been used in current airframe development. In JAXA's research project for design technology of high-lift device, fluorescent oil flow visualization was applied to realistic aircraft configuration model. At first oil flow method using fluorescence material was compared to the traditional method using titanium dioxide. Following that, as a result of the visualization, aerodynamic interferences between a nacelle and a wing, optimum position of the flap were obtained in relation to the aerodynamic performance.

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The management of drag acting on solid surfaces by water flow is important for saving energy of ship and pipelines. The present author has investigated the drag on algal blades and dolphin skins as examples of the bio-inspired management of drag. This report demonstrates our recent numerical and experimental results, such as a decrease in the wall-shear stress by the polysaccharide models on the deforming film and the low values of drag coefficients of the small wavy plate. These changes in drag are caused by the modification of coherent structure near the functional, deformable surfaces of sea life.

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Drag-reducing ability of three kinds of seal fur surfaces, four kinds of PTFE (Poly-Tetra-Fluoro-Ethylene) pile surfaces, and a hybrid riblet surface was tested in a rectangular channel flow using water and a glycerol-water mixture. The pressure drop along the channel was measured in order to evaluate friction factors, i.e., drag reduction ratios in a wide range of Reynolds number conditions.

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The properties of jets produced by dielectric barrier discharge plasma actuators (DBD-PA) have been investigated by using a particle image velocimetry (PIV) system. A DBD-PA with a doughnut-shaped electrode generates annular wall normal jets by applying high voltage (V) and high frequency (f_p) signals between top and bottom electrodes. Variations of velocity distributions of wall normal jets affected by voltage surge velocities (dV/dt) are estimated in the range of 150≤dV/dt≤250 volts/μsec. The inclined and oscillating wall normal jets can be formed by using a DBD-PA with an opposing pair of electrodes and applying independently signals between their electrodes.

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We have developed a suitable drag reduction additive(LSP-01) and applied the additive for more than 120 practical distinct heating and cooling systems. As an example, the proof verification of the Sapporo city office is reported in this paper and the approach for the energy saving technology with LSP-01 is presented.

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