Recently, researches of a new rapid transport system “Aerotrain” using natural energy resources have been continued, as one of approaches to various global environmental problems. In order to put the Aerotrain into practical use, to improve running stability is one of the research assignments. The Aerotrain which has vertical side wings at each tip of main wings arranged in tandem is able to get high lift-to-drag ratio and save the driving power by ground effects between the main wing and ground, and between the side wings and sidewalls. However, the wing in ground effect has inevitably a pitching instability, because the unsteady aerodynamic characteristics such as lift, drag and moment coefficients depend on the height of the wing above the ground. Hence, it is difficult to get the self-stability only airframe configuration for the Aerotrain. For this reason, the aileron-flaps are used to run the Aerotrain stably. In this paper, we simulated the flows around the wing of the 3^rd model (ART003) with aileron-flaps using thermo-fluid numerical analysis software FLUENT. As a result, we clarified the aerodynamic characteristics of the ART003 wing with aileron-flaps, and got the aerodynamic characteristics of the wing available to control the posture of the Aerotrain.

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Air-oil two-phase flows driven by a rotor with teeth are studied by a numerical simulation with an interface capturing Conservative Level Set method. The code has been developed on the rotating frame in cylindrical coordinate system. The experiments were also conducted and the snapshots of the oil distribution and the friction moment were compared with the numerical results. The pitch and the height of the tooth were taken as parameters to figure out the effect on gas-liquid interface profile and frictional moment. The behavior of the air-oil interface is in good agreement with the experiment at 100-rpm rotational speed. The detailed contribution of the pressure and the shear stress acting on the tooth surface is also understood. It is found that the numerical simulation is able to describe the two-phase flow very well at 100-rpm rotational speed and higher grid resolution is necessary in order to capture the phenomena at 500-rpm rotational speed.

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For compressible flow simulations, FDS, FVS, and AUSM are popular shock capturing schemes. However, these schemes do not work well for turbulent flow simulations because of their excessive numerical dissipation. On the other hand, the secondary conservative finite difference method is useful for unsteady turbulent flow simulations, although it does not work well for flows with discontinuities. In this study, we propose a computational technique that combine the shock capturing schemes and the secondary conservative finite difference. In addition, we try to combine the secondary conservative finite difference method and LAD (localized artificial diffusivity). These methods are combined properly with the aid of a shock detected sensor. In order to demonstrate the shock capturing performance and low numerical dissipation property of the hybrid schemes, numerical tests are done on a three-dimensional periodic inviscid flow, the shock tube problem (Sod problem), and a shock-vortex interaction problem. The computational results have shown that the proposed hybrid schemes based on numerical flux have desired conservation property, shock capturing performance, and low numerical dissipation in regions without discontinuity.

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A high-order numerical algorithm for incompressible flows with a compact finite difference method is proposed. There are some difficulties on the compact finite difference when a numerical simulation of incompressible flow is concerned. For instance, the effective matrix solver for discrete Poisson equation and the strategy to reduce numerical non-linear instability are still not clear for the compact finite difference methods. In this study, an effective matrix solver for discrete Poisson equation is selected and a method which reduces the numerical instability without any artificial dissipation or low pass filtering is proposed. These proposals are estimated on a numerical simulation of 3D periodic flow. Then, to demonstrate the reliability of the proposed method and to examine the effect of the grid resolution and the order of accuracy for high-order compact finite differences, the incompressible turbulent plane channel flow simulations are performed with and without SGS models. Finally, the large-eddy simulations of turbulent wavy channel flow are performed with a boundary-fitted curvilinear grid.

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Using the data of the direct numerical simulation (DNS) for the turbulent compressible channel flow with the isothermal walls, a priori test for the one-equation subgrid-scale (SGS) model for turbulent compressible flows is performed. It is comfirmed that the model expressions for the grid-scale (GS) viscous and diffusive terms, SGS temperature-dilatation term with the filtering DNS's heat flux, SGS stress-strain term are effective. The SGS stress and flux are modeled by using the GS strain and coherent structure model function. From a posteriori result of the large-eddy-simulation (LES) using the proposed SGS model, the present model can reproduce the DNS one qualitatively.

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We have proposed a one-dimensional simple model for predicting the performance of liquid crystal actuators by combining the motion of the upper plate of a liquid crystal cell and the flow of a liquid crystal. Comparison of the motion of the plate between the numerical predictions and the experimental results reported in the previous paper shows that the proposed model is useful to predict qualitatively the motion of the upper plate. By using the model, we have studied the rotation of the molecules and the velocity profiles between two plates. As a result, it is clarified that when the electric field is released, the molecule in the middle region between two plates returns to the initial angle completely at 1 Hz of the frequency of the applied voltage, it does not return to the initial angle but it takes approximately 40 deg at 10 Hz, and it oscillates around 90 deg with a small amplitude at 100 Hz. While its profile is S shaped in lower 10 Hz frequency, the induced velocity shows a double-S shaped profile in higher 20 Hz frequency. Such the peculiar velocity profile stems from the so-called kickback effect. The maximum shear stress acting on a wall reaches 20 Pa in frequency of 20 - 30 Hz. This frequency range is coincident with the frequency at which the double-S shaped profile begins to occur.

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When visualizing large-scale particle systems, it is difficult to maintain adequate framerates because we have to render dynamic scenes with a large number of small spheres. For the control of trade-offs between the overall image quality and total rendering speed, we propose a new rendering scheme which uses a fast method based on shaded texture mapping and a high-quality implicit surface method in a combined way. The shaded texture mapping, which generates a pseudo-texture through alpha-blending a proper portion of template texture for shade and highlight onto a base spherical texture, can render a particle faster than the implicit surface method. However, a weakness of the texture mapping lies in its poor shading quality. In contrast, the implicit surface method is accurate enough for analyzing particle systems visually. Actual method to render each particle is decided according to the viewing distance; the high-quality method is chosen only when the distance is smaller than a threshold, to allow the user to observe the region of interest closely. We use a molecular dynamics simulation dataset to evaluate the effectiveness of our scheme empirically. In addition to this, we also consider the extensibility of our scheme in terms of framerate stability, scalability, and expressiveness.

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We present a simulation of meso-scale fluid in a grooved channel conducted using the many-body dissipative particle dynamics (MDPD) method. The simulation system consists of a straight channel with a rectangular groove and a liquid that fills the channel. In the simulation, an instantaneous liquid interface was defined and the time-series variation of the angle between the channel wall and the interface was investigated. The calculated angle was found to satisfy the Gibbs' inequality condition when the interface passes the corner of the groove. We also investigated the behavior in which the liquid filled the groove by varying the contact angle between the liquid and the channel wall. The results show that the feasibility of filling the groove, which depends on the contact angles between the liquid and the grooved/non-grooved channel wall, qualitatively agrees with the geometrical analysis. We also showed that a smaller contact angle between the liquid and the grooved channel wall and a larger contact angle between the liquid and the non-grooved channel wall causes the liquid to fill the groove.

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Continuous flexible thin material, such as paper, textiles, and plastic films, are referred to as webs. At present, web machines are used in various fields. However, a number of problems regarding web handling industries remain to be solved. Generally, webs are transported through rollers. When a web is transported at high speed, the surrounding air enters the gap between the web and the roller and forms an air film. The air film prevents scratches and stains because it eliminates the contact between the web and the roller. However, the air film generates slip due to the reduced traction, which is a serious problem for web production. Therefore, control of the air film thickness has become important. In the present study, measurement of the air film thickness is conducted using a PET film as the web. An experiment is carried out to examine the effect of changing the relative velocity between the web and roller. In addition, flow visualization is conducted in the inlet and outlet areas of the web wrap region using particle image velocimetry (PIV). As a result, the effect of the air flow between the web and the roller on the air film formation and the characteristics of the flow near the inlet and outlet areas are clarified.

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The effect of design parameters on natural convection heat transfer from horizontal heated plates in an enclosure is investigated experimentally. Our experimental setup is described as follows: Two heated plates are arranged in the vertical direction. The temperature of the ceiling is maintained at a constant low temperature. The other sides satisfy the thermal insulation boundary condition. To clarify the effects of the design parameters, the relationship of heat transfer to the heat flux and the aspect ratio of the enclosure were examined. The results show that the flow characteristics have two distinctive patterns: one includes vortex motion, and the other comprises a flow along the heated surface. An increase in the heat flux promotes vortex motion and enhances heat transfer. The heat transfer is independent of the height of the adjacent air space. The heat transfer from the heated surface that gives rise to the vortex motion is not influenced by the enclosure diameter, whereas the heat transfer from the other surfaces increase linearly with the enclosure diameter. Nusselt number is expressed as a function of the modified Rayleigh number and the nondimensional enclosure diameter.

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A fluid solver using signed distance function (SDF) for shape representation was developed based on the immersed boundary method to simulate incompressible viscous flows. The forcing velocities near boundary are extrapolated by trilinear interpolation with taking into account a boundary condition using SDF. SMAC method is employed for solving basic equations for unsteady incompressible flows. The equations are discretized in space by 2nd-order central difference method, where the discretization near boundary is improved by SDF to satisfy a Dirichlet boundary condition for velocity. The fluid solver was verified in both steady and oscillating three-dimensional Poiseuille flows. As the grid spacing decreases, L² and L^∞ norm of the error of the axial velocity profile respectively decrease by the order of 1.96 and 1.89 for the oscillating flow. Therefore, the fluid solver enables to analyze the Poiseuille flow using Cartesian mesh by 2nd-order of accuracy in space.

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A simple theoretical expression for the evaporation/condensation coefficient in equilibrium has been proposed by Nagayama and Tsuruta based on the transition state theory and molecular dynamics simulations in 2003. It is not clear, however, whether this approach can be applied to complex molecules such as n-dodecane with long chain structures. In this study, molecular dynamics (MD) simulations have been performed to investigate the evaporation/condensation coefficients of n-dodecane in equilibrium systems. It is found that the evaporation coefficient of n-dodecane primarily depends on the translational energy and the surface temperature similar to simple molecules like argon and water, while the molecular orientation of long chain n-dodecane has less effect. Also, the MD data of n-dodecane agree well with the theoretical expression based on the transition state theory. We conclude that the evaporation coefficient can be predicted by the translational length ratio of liquid to vapor in general even for the long-chain molecules.

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In the case of engine bearings, pressure in a cylinder is necessary for the analysis of lubrication. In this study, a cycle simulation of gasoline engines has been developed to predict the pressure in a cylinder under the wide range of engine operation. In the cycle simulation, intake and exhaust processes are included and combustion process is calculated with flame propagation based on burning velocity. The pressure in the cylinder is introduced into the bearing analysis to calculate the load on the bearing in addition to the inertia force. Orbital movement, minimum oil film thickness, and power loss in the bearing are estimated. This method may be useful on an engine design.

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The effects of fuel ignitability on the stable operating range of premixed low temperature diesel combustion (LTC) were investigated. With the intake oxygen concentration set at 14% and the injection timing at 30 °CA BTDC, the operating load range is almost unchanged for fuels with cetane number above 40; while with cetane number below 40 both the high and low load limits increase significantly with decreasing cetane numbers, the low load limit increases more steeply, resulting in a narrowing of the load range. When keeping the combustion phasing constant at TDC by controlling the injection timing, smoke emission limits at the higher load operation for high ignitability fuels and abrupt combustion for low ignitability fuels become problems, but a decrease in the intake oxygen concentration is effective to expand the high load limit. The low load limit can be expanded with the combustion phasing held constant at TDC, and it can be further expanded when increasing the intake oxygen concentration, at the expense of increases in NOx emissions however. Finally, the effects of fuel ignitability on the range of injection timings for stable LTC operation are also examined.

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Characteristics of diesel combustion with low cetane number fuels with similar distillation temperatures to ordinary diesel fuel, including fuels with cetane number 32 and 39 (LC32, LC39), and a blend of normal cetane and heptamethylnonane with cetane number 32 (CN32), were investigated. The effects of cooled EGR and pilot injection on combustion and exhaust gas emissions with these fuels were examined in a single cylinder diesel engine equipped with a common-rail type fuel injection system. Even with the low cetane number fuels, quiet combustion with low levels of exhaust gas emissions comparable to ordinary diesel fuel was established by suitable control of intake oxygen levels and pilot injections. At light and medium loads, low smoke, low NOx, and quiet combustion is possible by decreasing intake oxygen concentration with EGR. At high loads, pilot injection can suppress NOx emissions and the maximum rate of pressure rise to levels similar to ordinary diesel fuel. Smoke emissions at low intake oxygen and NOx emissions at high intake oxygen with the low H/C ratio fuel, LC32, are higher than with CN32, the high H/C ratio fuel at the same cetane number.

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Recently, Urea-SCR system is used for reducing NOx emission from diesel engine. In the Urea-SCR system, aqueous urea is injected into the exhaust gas flow where it evaporates and decomposes to NH₃. It is necessary to clarify the generation process of NH₃ in high temperature atmosphere for the improvement of NOx reduction performance. In this study, the generation behavior of NH₃ and the mass reduction of solid urea and 32.5wt% urea solution were measured in a high temperature vessel. As a result, the start of NH₃ generation became early and the maximum NH₃ concentration increased with increasing temperature in the decompositions of both samples. The start of NH₃ generation in the urea solution decomposition was later than that in solid urea decomposition owing to the evaporation of water. Moreover, the amount of mass reduction rate was increased when N₂ was passed through the vessel. It seemed that the reaction of urea was accelerated because reaction products were removed by the N₂ flow. As for the residue after decomposition, the mass of residue decreased with increasing temperature in the decompositions of both samples. The residues of them were decreased when N₂ was passed through the vessel under lower atmospheric temperature conditions.

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