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It is known that small quantities of surfactant additives can greatly reduce the friction factors. This is because the generation of turbulent vortices is suppressed by the formation of rod-like micelles, and the flow remains laminar. However, the heat transfer coefficients decrease during flow laminarization. The research objective is to examine heat transfer enhancement effects by air injection. This paper presents an experimental investigation on the heat transfer characteristics in an air-surfactant solution two-phase flow through a vertical tube. Heat transfer coefficients and friction factors were much larger for the air-surfactant solution two-phase flow than for surfactant solution. However, they were smaller than an air-water. It seems to be due to drag reduction effects of micelle structure. The flow patterns were investigated by visualization. The flow pattern of air-surfactant solution two-phase flow changed from a slug flow to a churn flow or from a churn flow to a bubbly flow at low liquid phase Reynolds number compared with the case of air-water two-phase flow on fixed air flow rate.

The spray combustion is applied to various practical combustors such as a diesel engine, a gas turbine, etc. However, the spray combustion is the very complicated, unsteady and inhomogeneous physicochemical phenomenon composed of preheating, evaporation, mixing, ignition, combustion and quenching, etc. Chiu et al. considered the spray combustion field with the concept of group combustion, and proposed that the group combustion can be classified into four modes in terms of group combustion number. In this paper, we examined to improve Chiu’s group combustion mode using the numerical analysis on gas phase combustion process in three-dimensional inhomogeneous concentration and temperature fields of methane-air mixture. We arranged many fuel points using random variables instead of fuel droplets, and changed the initial equivalence ratio and fuel point diameter. We obtained the following results; 1) The group combustion is classified into five modes in terms of the initial equivalence ratio and fuel point diameter. 2) The ignition occurs in each fuel point when the mixture gas is lean, while the ignition occurs in the area with fuel point closely spaced when the mixture gas is rich. 3) "The initial equivalence ratio / fuel point diameter" is the appropriate parameter of the group combustion of gas phase.

The Particle Tracking Velocimetry, so-called PTV, is one of the most promising methods to measure instantaneous two dimensional flow fields in detail. In this paper, a new method to estimate vorticity distributions of the two dimensional flow fields which are measured by the particle tracking velocimetry is proposed. Velocity vectors obtained by a particle tracking velocimetry locate randomly on a two dimensional plane. The proposed method fits quadratic surfaces to the measured velocities in an interrogation area. The vorticity is evaluated by differentiating the fitted quadratic surfaces. The optimal size of the interrogation area is determined by Monte-Cairo simulation. The proposed method is applied to the PTV measurements of wind wave experiments., 本文データの一部は、CiNiiから複製したものである。

This paper discusses the wind tunnel tests for a tall building model having either viscous or visco-elastic damper under the turbulent boundary layer flow. The wind tunnel tests are carried out either the across- or along-wind direction for the viscous and the visco-elastic damper systems, respectively. This wind test set-up includes a special measurement system to obtain the damper hysteetic loop, then the response property of damper and system are discussed by the referring to the obtained loop. In case of the severe wind speed, the response of visco-elastic system is smaller than the viscous system because the stiffness of visco-elastic damper contributes to the stiffness of system.

In a core wall system high-rise building, the center core of which consists of four L-shaped core walls, under the action of a diagonal seismic force, the axial load of the core wall is very high. Particularly the corner and the area near the corner of the L-shaped core wall are subject to high compressive stress. Reinforcing these areas is therefore considered effective in improving the deformation capacity of the core walls. In this paper, compression tests were conducted on square and rectangular sections of columns which simulated the corner and the area near the corner of the L-shaped core wall.

Natural convection is suppressed in space environment due to the weightlessness. Only centrifugal force is utilized currently to drive gas-phase thermal convection in space. This paper presents an alternative way to drive thermal convection. From the investigation of combustion oscillation in rocket motors, a new thermal convection had been found in stationary acoustic fields. Analyzing the phenomena, acoustic radiation force is found to be the candidate driving force. With a simplified system using a hot wire as a cylindrical heat source, the characteristics of the convection in acoustic field are investigated experimentally. A numerical modeling that includes the radiation force succeeded in reproducing the convection. Knowledge for further application is obtained., 資料番号: AA0063349021

Air bubble entrained in oils cause many problems, such as the acceleration of oil degradation, cavitation erosion, and decline of effective bulk modulus of oil. Air bubbles in working fluids must be actively separated and eliminated to realize performance improvement of hydraulic systems. To remove air bubbles from hydraulic oil, it is possible to use an active "bubble eliminator" that uses swirl flow to remove air bubbles. In this paper, the improvement of oil aging, cavitation erosion, and the effective bulk modulus by the bubble eliminator was experimentally investigated. Moreover, to enhance the performance of the bubble eliminator, experimental flow visualization and numerical simulation of the bubble eliminator were conducted, and the importance of design index of the bubble eliminator considering the fluid condition \WS mentioned. To establish the new design index of the bubble eliminator, the effect of the shape parameters of the device andfluid condition on the performance of the bubble eliminator was clarified. As a result, it became possible to design the bubble eliminator considering the fluid condition.

The smoothed particle hydrodynamics (SPH) method developed by Lucy, Benz, Gingold, Monaghan and Liversky has a problem of numerical disorder at the boundary of 2 phase flow as gas and liquid. In this paper, new formulas of SPH method, named Relaxation equations, suited for treating 2 phase flow of non-viscous fluid are proposed. The Relaxation equations are constructed based on the mass conservation equation and the momentum conservation equation. By using the formulas, it is possible to suppress numerical disorder around the boundary of 2 fluids., relation: isVersionOf: http://ci.nii.ac.jp/naid/110006148743/

The popularization of both small-sized and large-sized wind turbines is indispensable for the popularization of wind power generation. Though many small-sized wind turbines are manufactured in the world, most of them are not suitable for the special wind conditions in Japan, which are characterized by frequent change of wind direction and heavy turbulence. This paper describes the results of the characteristics test of a small-sized perpendicular-axis type wind turbine to identify the conditions of a small-sized wind turbine suited to Japanese wind conditions.

This paper proposes a two-dimensional vortex method, based on Vortex in Cell method, for gas-liquid two-phase free turbulent flow. The behavior of vortex element and the bubble motion are calculated through the Lagrangian approach, while the change in the vorticity due to the bubble is analyzed in the computational grids resolving the flow field. Therefore, the numerical procedure corresponds to the Lagrangian-Eulerian method. The present method is applied to simulate the bubbly flow around a square-section cylinder. The simulation demonstrates that the bubble entrainment into the Kármán vortex and the resultant reduction for the strengh of the vortex are successfully captured by the method. It is also confirmed that the vortex shedding frequency and the pressure distribution on the cylinder are favorably compared with the measured results.

Authors proposed a numerical model for the inelastic analysis of three-dimensional frames including L-shaped shear walls in part 1: Constitutive equations. In the present paper, We made the hysteresis model of the slip spring which was one of the plastic elements considered in this numerical model newly, based on our experimental slip data of wall bottoms. Then, we compared the analytical results applying the numerical model to L-shaped shear walls with boundary beams with our experimental data. According to the comparison result, the analysis of the numerical model expresses the main characteristics of L-shaped shear walls sufficiently.

In high-rise buildings with the core wall system, the axial load of the core wall is remarkably very high under the action of a diagonal seismic force. Particularly the area near the corner of the core wall is subject to high compressive stress. Reinforcing these areas is therefore considered effective in improving the deformation capacity of the core walls. In this paper, based on the lateral loading tests results of L-, T-, H-shaped core walls and wall columns, edge confinement index was proposed. The relationship between edge confinement index and limit drift angle was shown.

Many investigators have precisely carried out the measurements of drag forces on a sphere and a cylinder. However, it has been difficult to expound the theory of the drag forces, because of the pressure drag caused by a separation flow. The separation point changes according to Reynolds number, and follows a wake flow. This wake is formed Karman vortex street, which is caused a vibration force by its alternate wakes. In this paper, visualization experiments have been carried out to observe the separation point and Strouhal number of spheres and cylinders. A hydrogen bubble method and a dye injection technique have been applied to visualize the separation point and the wake flow in this experiment.

In this paper, advanced drag prediction method based on the momentum conservation theorem was applied to CFD computational results of transonic flows. This method can decompose total drag into drag components such as wave, profile, induced and spurious drag which is due to the effect of the numerical diffusion and error. In this method, drag components are computed by the volume integration of entropy production or vorticity terms in the flow field around the aircraft. Therefore, wave/profile drag can be computed by the partial volume integration of the entropy terms around the shock waves/boundary layer and wake, respectively. Then, spurious drag can be computed by the volume integration of the entropy terms at the remaining flow field. It is because the entropy production in the flow field should occurred within shock, wake and boundary layer regions from the viewpoint of physics. Induced drag can be computed by the integration of the vorticity terms related to the wingtip vortex. This drag decomposition method was applied to structured/unstructured mesh computational results. The computational results showed that the drag decomposition method had good capability of the drag prediction and meaningful drag decomposition. Moreover, the more accurate drag prediction was realized by the elimination of the spurious drag component from the total drag., 資料番号: AA0049212002, レポート番号: JAXA-SP-05-017

When computational simulation for low Mach number flows is conducted with a compressible flow solver, its performance deteriorates in terms of both convergence speed and accuracy. The deterioration of accuracy is caused by excessive artificial viscosity in low Mach flow regions. In order to improve convergence of an iterative method, a local preconditioning method for low speed flow is frequently used. The preconditioning method minimizes the wave speed range between a particle wave and an acoustic wave. When the preconditioning method is applied to an upwind scheme, its artificial viscous terms need to be modified by preconditioning matrix. This modification cures the accuracy problem of calculated flows in the low-Mach flow regions. In this paper, the effects of the preconditioning method on unsteady calculation of flows around an airfoil are discussed., 資料番号: AA0049212026, レポート番号: JAXA-SP-05-017

An automated design optimization process is applied to both single and multi objective optimization problems of scramjet engine inlet design. This optimization process integrates together an optimizer with a mesh generator, a flow solver, and an objective analysis tool into an automated optimization loops because the flow simulation is required for every step along the line search and finding the feasible direction. This paper presents the implementation of these new design techniques by the gradient-based optimizer Sequential Quadratic Programming (SQP) and their application to scramjet engine inlet case in flight condition of Mach 8. The performance of scramjet inlets with uniform inflow is improved, and the optimized functions, that is, the total pressure recovery coefficient increases. The trade-off (also known as the e-constraint) method is applied and implemented to find the Pareto optimal set formed by the no dominated solutions of the feasible design. The objective functions are the total pressure loss and the drag, and some solutions are obtained to analyze the relations between the total pressure loss and the drag., 資料番号: AA0049212012, レポート番号: JAXA-SP-05-017

Structure of single bubble is classified into six types. Although bubbles are often seen in everyday life, a couple of types, a water droplet drifting on water surface and an anti-bubble, that is water droplet wrapped with air film, are regarded as unfamiliar phenomena. Mechanism of the air film stability is discussed in comparison with soap film stability. This paper presents a possible mechanism that sliding and rotation of a water droplet stabilize floating droplet and anti-bubble with preventing air films from losing their thickness. Transpoting air by capillary wave on the droplet surface is also a candidate of the stabilization mechanism. Step-by-step decrease of diameter in collapse of a droplet is explained by the concept of capillary wave.

A versatile numerical method of flows with complex boundaries is highly needed in many hydraulic practices. This paper presents a new computational approach for shallow water flows with the emphasis on the accurate modeling of complex geometries in the Cartesian coordinate system. Expanding the concept of CIP-CSL2 scheme, the present method simultaneously solves point, line and area averaged values of a computational cell to directly capture the effects of complex boundary shapes and conditions. The method is then tested against the one-dimensional dam-break problem to find good agreement with theoretical results. Further, the applicability of the method is demonstrated for two flows. In one case, hydraulic bores bounce from impermeable walls and in the other case water flows between narrow impermeable walls whose direction is arbitrary, both of which are known to be tough problems.

In this paper we attempted to develop a low-noise 'Active Turbulence Generator (ATG)' for aerodynamic noise measurement in a large scale turbulent flow field. The aerodynamic noise from the developed ATG was only 10 dB larger than that of the conventional wind tunnel. Aerodynamic noise from a rearview mirror was measured to estimate sound generation effect on turbulence intensity. The experimental result showed that the edge tone of the rearview mirror was disappeared in the case of strong turbulent flow field. Aerodynamic noises strongly depend on the turbulence intensity and eddy scale of incoming flow. The turbulence of incoming flow is important parameter to estimate flow around real cars. The active turbulence generator is one of the useful devices to simulate real road simulations in wind tunnels., 資料番号: AA0049208017, レポート番号: JAXA-SP-05-012

A versatile numerical method of flows with complex boundaries is highly needed in many hydraulic practices. This paper presents a new computational approach for shallow water flows with the emphasis on the accurate modeling of complex geometries in the Cartesian coordinate system. Expanding the concept of CIP-CSL2 scheme, the present method simultaneously solves point, line and area averaged values of a computational cell to directly capture the effects of complex boundary shapes and conditions. The method is then tested against the one-dimensional dam-break problem to find good agreement with theoretical results. Further, the applicability of the method is demonstrated for two flows. In one case, hydraulic bores bounce from impermeable walls and in the other case water flows between narrow impermeable walls whose direction is arbitrary, both of which are known to be tough problems.

Pattern formation in flow between two corotating disks in an enclosure is investigated numerically and experimentally. The outer cylindrical boundary of the flow field is assumed to be fixed, whereas the inner cylinder rotates together with the two disks. The flow is not only symmetric with respect to the inter-disk midplane but also axisymmetric around the axis of rotation at small Reynolds numbers. The axisymmetry of the flow field is broken due to instability at high Reynolds numbers. Such an instability occurs for small gap ratios, the ratio of the gap between two disks to the radius of the annulus, and yields a polygonal flow pattern in a plane normal to the rotation axis. We identified two kinds of three dimensional unsteady flow by numerical simulations, one of which is asymmetric with respect to the inter-disk midplane and the other has a shift-and-reflect symmetry with the midplane, and compared them with those obtained by experiment. We found that the critical Reynolds number at which the axisymmetric makes a transition to unsteady 3D flow is smaller than those evaluated in previous papers, although the flow patterns are consistent with those reported in them., 資料番号: AA0049208024, レポート番号: JAXA-SP-05-012

The Deployable Radiator (DPR) with looped heat pipe is planed in Engineering Test Satellite. The loop heat pipes are able to transport heat over long distances in satellite. The thermal control systems such as the loop heat pipes are demanded with precise control and expected to operate on orbit for 10 to 20 years. The non-condensable gas in loop heat pipe with working fluid affects the precise control and performance. The paper describes an investigation into operating characteristics of loop heat pipe in DPR and an effect of non condensable gas., 資料番号: AA0049054003, レポート番号: JAXA-SP-05-008

A new adaptive mesh refinement method for unsteady compressible flow is presented in this paper. For unsteady flow problem, the solution-adapted grid is also dynamically changing its shape at every time step according to the flow change since the flow is non-stationary. For the present solution-adapted grid method, two grid cells are merged into one grid cell and one grid cell is divided into two grid cells according to a criterion of grid adaption in a time-dependent way in unstructured grid system. In this case, it is important to assure geometric conservation low as well as physical conservation low on such the grid system. Therefore, we adopt a finite volume method in which a control volume on the space-time unified domain for estimating numerical flux. The method is described and applied for two-dimensional unsteady compressible flows.

After the Tokachi-0ki earthquake, earthquake proofing of cylindrical tanks are demanded. In particular, the measure against a sloshing is demanded. However, there is not a method obtaining effective result in an actual tank. In this paper, we propose a wave height reduction method and explain about effects of it. This proposed method is used a support and a flat board as an instrument. At first, we performed an experiment of a shaking table using the cylindrical tank's model. We examined the wave height and the wave pressure of the sloshing. When we used the proposing method, we measured the wave height and the wave pressure too. Next, in numerical analysis, we calculated sloshing wave height in a condition same as an experiment and examined the propriety of numerical analysis.

The shock capturing analysis by using FEM (Finite Element Method) is described. The artificial viscosity is necessary for stable calculation to capture the shock wave, but it decreases the accuracy of solution. In this paper, the artificial viscosity is discussed from the viewpoint of SUPG (Streamline Upwind Petrov-Galerkin) method and tensor viscosity. The strain invariant is used in order to judge the region to operate the artificial viscosity. Flowfield around the sphere and cylinder under several Mach numbers are calculated, and good correlation between numerical and experimental results are obtained. The transonic flow can be also simulated by this FEM.

A computational fluid dynamics (CFD) code with partial cells in Cartesian coordinate (PCC) method has been developed. The merit of this method is that input data preparation time is extremely short because computational mesh data are separated from geometry data. However, a general Cartesian coordinate method has a big subject in calculation accuracy. One of the factors is precision in geometry expression around the complicated shape, and another is a turbulence model near the wall because mesh is independent from the boundary and not fitted with it. Therefore, discretization equations were derived based on Finite Volumetric Method, and a combination of the wall function and a low Reynolds number k-ε turbulence model was proposed here. This paper describes implementation of this method and shows the results compared with experimental data by particle image velocimetry (PIV) at the steady flow in the cylinder of a 4-valves S.I. engine. The comparison results of velocity vector maps show good agreement between CFD and PIV.

This paper describes a new monolithic approach based on the Pressure Poisson Equation (PPE) to solve interaction problems of incompressible viscous fluid and an elastic body. The PPE is derived so as to be consistent with the coupled equation system for the fluid-structure interaction (FSI). Based on this approach, we develop two efficient monolithic methods. In both methods, the fluid pressure is derived implicitly so as to satisfy the incompressibility constraint and all the other unknown variables are derived fully explicitly or partially explicitly. The coefficient matrix of the PPE for the FSI has characteristics of (a) symmetric and positive definite feature, (b) reduction of degrees of freedoms to be solved, and (c) less dependence of the condition on material properties. The arbitrary Lagrangian Eulerian method is employed for the fluid to take into account the deformable fluid structure interface. To demonstrate fundamental performances of the proposed approach, the developed two monolithic methods are applied to simulate the vibration of a rectangular cylinder induced by vortex shedding.

This paper describes a strong coupling method considering non-conforming mesh on fluid-structure interface. In the present method, a transformation matrix derived from the geometrical relations between non-conforming fluid and structural meshes on fluid-structure interface is directly combined with the formulation of the strong coupling method to satisfy the compatibility and equilibirium conditions on fluid-structure interface. The conjugate gradient method is applied to solve the derived coupled equation system by introducing the consistent pressure Poisson equation. To verify basic characteristics of the proposed method, it is applied for free vibration of a cylinder in quiescent fluid. The added mass and damping coefficients derived by the present method agree well with those by other researchers.

Heat transfer between fluid and solid, which occurs in heat exchangers, steam generators and so forth, is one of the most important phenomena in the field of engineering. In this paper, a coupling phenomenon including flow of thermal fluid and heat transfer in a solid is analyzed using the finite element method on a large scale PC-cluster system, the RIKEN Super Combined Cluster (RSCC). To estimate thermal interaction between fluid and solid, both flow of thermal fluid and heat transfer in solid must be considered. As a unified method for the coupling analysis, a method based on the assumption that the solid is a virtual fluid in which the flow velocity is zero is selected. The flow of the thermal fluid and heat transfer in the solid can be simulated by solving the same governing equations. Almost all processes of the computation can be parallelized because an exchange of thermal boundary conditions between the fluid and the solid is not necessary. High parallel efficiency is achieved on parallel environment. Internal and external thermal flows of a tube array are analyzed with consideration of heat transfer. Flows around a heatsink mounted on a CPU and heat transfer in the heatsink are also analyzed. It is confirmed that the computation of the coupling phenomenon can be achieved with high parallel efficiency on the large scale PC-cluster system using this approach., 資料番号: AA0048469019, レポート番号: JAXA-SP-04-012

In the combustor of the dual-mode ramjet engine, a Pseudo-Shock Wave (PSW), mixing and combustion are closely coupled with one another and cause complicated interactive phenomena. It is difficult to clarify the relation between the heat added by high temperature jet and the formation of the PSW only by experiment. In the present study, the PSW produced by the high temperature jet in constant area square duct was investigated by both experiment and numerical simulation to clarify the relation between the heat addition by the high temperature jet and the formation of the PSW and the PSW created by the backpressure of the test section in diverging duct which resemble shape of the combustor was investigated by numerical simulation to research the structures of the PSW and the changes of flow in diverging duct. Numerical simulations were carried out for three-dimensional configurations. The governing equations are the Navier-Stokes equations with the k-omega SST two-equations turbulence model and the chemical reaction did not consider in this numerical simulations. This paper describes about the behavior of the PSW produced by the high temperature jet and the detail of the interaction between the high temperature plume and the low temperature supersonic flow based on the experimental and computational results, and the structures of the PSW produced by the backpressure of the test section and the asymmetric characteristic of flow in diverging duct based on the computational results., 資料番号: AA0048469037, レポート番号: JAXA-SP-04-012

JADC is conducting High Speed Transport Program (HSTP) aiming for the development of next generation high speed aircraft such as supersonic and transonic speed transport. In the FY2003, the aerodynamic design of high lift device as a part of this program were performed. This paper describes the optimum design of high lift device to improve the lift-to-drag ratio (L/D). The optimization process is based on the response surface method, where the effects of flaps are estimated by linear superposition. Navier-Stokes calculations are performed for the model either with leading-edge flaps or with trailing-edge flaps. Then the performance of the model with all flaps deflected is predicted by adding the effect of leading-edge flap and that of trailing-edge flap. The response surface is created for search of optimum value. This method reduces the computational time required for CFD analysis. Results of Navier-Stokes calculation for the optimum configuration indicate that the present method yields reasonable results., 資料番号: AA0048469015, レポート番号: JAXA-SP-04-012

In this paper, flow computations around a 3D high-lift configuration with three-element (slat-main-flap) wing were performed on structured and unstructured meshes. The results were used to analyze and improve the accuracy and reliability of the aerodynamic analyses for high-lift system. Computed lift and drag coefficients both on structured and unstructured meshes showed good agreement with the experimental data. In the computations, it was also shown that further mesh refinement should be used to improve the resolution for slat wake, wing tip, and trailing edge for more accurate prediction by detail comparison with wind tunnel test data and computational data., 資料番号: AA0048469013, レポート番号: JAXA-SP-04-012

This paper deals with the exchange flow under the unstably stratified field. The author developed the effective measurement system as well as the numerical analysis program. The system and the program are applied to the helium-air exchange flow in a rectangular channel with inclination. Following main features of the exchange flow were discussed based on the calculated results.(1) Time required for establishing a quasi-steady state exchange flow.(2) The relationship between the inclination angle and the flow patterns of the exchange flow.(3) The relationship between the concentration profile and the inclination angle.(4) The relationship between the net in-flow rate and the inclination angle.(5) The comparison of the computed velocity profile and the net in-flow rate with experimental data.A good agreement was obtained between the calculation results and the experimental results.

This paper presents a numerical simulation on the incompressible viscous flow around a moving particle.

This paper presents current status and issues of aircraft drag prediction using numerical methods based on Reynolds-averaged Navier-Stokes equations (RANS) in JAXA. Several results on an airfoil and aircrafts show the prediction of aerodynamic drag is very sensitive to grid density and numerical schemes as well as transition in boundary-layer. Although state-of-the-art RANS CFD can not satisfy the requirement for aerodynamic design of aircrafts enough, it already provides almost the same reliability as wind tunnel tests in some cases. To overcome the issues in the prediction reliability, tighter cooperation between numerical and experimental methods is important besides efforts to improve numerical schemes and turbulence models., 資料番号: AA0047776019, レポート番号: JAXA-SP-04-002

In this paper, the three-dimensional models of divergent and convergent flows of non-Newtonian fluids in non-Archimedes spiral discs which are the core components in disc extruders, are studied by investigating the melting, mixing and flow mechanisms of a disc extruder. The distributions of velocity, pressure and viscosity in the gap between revolving and stationary discs were obtained by applying the commercial finite element analysis software-ANSYS. At the same time, the influence of disc configuration parameters and operational conditions on the flow field were investigated. The preliminary investigations provide not only a theoretical basis for application and serial development of this type of equipment, but are also an important reference for the study of kneading technology and theory in related disciplines.

The large sized solar arrays of satellite are installed in the fairing section of by being folded up. So the thickness of air layer between two panels is very thin comparing with the in-plate size of the panel. Because the panel is extremely light, the vibration of the panel is affected by the air layer. This paper presents that the effects of layer thickness on frequency of a panel including viscous, incompressibility air., 資料番号: AA0047427036, レポート番号: JAXA-SP-03-002

A hybrid method that combines the calculation of unsteady flow by large eddy simulation (LES) and the evaluation of acoustical performance by a compact Green's function is proposed to provide detailed information on the vortices in the flow that contribute to the generation of aeroacoustic sound. This paper clarifies the noise reduction mechanism of pantograph horns with periodic holes numerically and proves that the intermittent flow through holes suppresses the strength of dipole sound sources at the shear layer and collapses the large two-dimensional structure of sound sources in the spanwise direction., 資料番号: AA0047427003, レポート番号: JAXA-SP-03-002

When a bluff body is oscillated in a still fluid, secondary streaming is generated around the body. The objective of this study is the flow mixing and diffusion using this secondary flow that induces around the oscillated body. In this paper, the observed flow patterns using the visualization method around oscillated square cylinder was reported and was made a comparison the flow pattern between the both cases of the square cylinder and the circular cylinder. And three-dimensional flow structures around the oscillated square cylinder has been made clear. The experiments are carried out for the cases of Keulegan-Carpenter number KC between 0.4 and 2.0 and nondimensional frequency β=40～140

It has been verified by many researchers that the lattice Boltzmann method has the ability to simulate the viscous fluid flow as precisely as the finite difference method. The incompressible viscous fluid flow in the inlet section of two-dimensional channel are computed by the lattice Boltzmann method. In this paper, the computed results by the lattice Boltzmann method are compared with the results using finite difference method, and are discussed for the concave velocity profiles at the initial stage of development channel flow.

On duct system in industrial plants and air conditioners, free convection is produced by buoyancy forces in the fluid because of the temperature differences between the duct wall and the fluid. As a result, it was indicated that secondary flow vortices in a cross section of the duct occur, and counter-rotating additional vortices arise in a region near the bisector of the bottom wall at high ReRa. In this paper, steady laminar flows with free convection in horizontal rectangular ducts are studied numerically for air (Pr = 0.73) at ReRa =10^5, 8 × 10^5 on high aspect ratio. The effects for flow patterns of additional vortices on axial velocities, temperatures, stream lines of secondary flow, friction losses and Nusselt numbers are presented.

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.

The present paper has dealt with the one-sidewall cooling effect of spherical adsorbent paticles packed in a rectangular bed on water vapor adsorption characteristics by a 2-dimensional numerical analysis. The analysis model was considered that one-sidewall of a rectangular packed bed with the homogeneous spherical silica-gel particles was cooled and another walls were adiabatic. The moist air flowed into the rectangular packed bed with spherical adsorbent particles. The silica-gel B with high adsorption ability over high relative humidity was selected as a suitable adsorbent. Numerical results revealed the effects of moist air inlet humidity and airflow velocity, size of spherical silica-gel particles and width of the rectangular packed bed and the sidewall cooling terperature on the amount of water vapor adsorption., 住宅・ビル空調分野では、省エネルギーの促進や室内空気質そしてアメニテイ性の向上が米国やカナダように一部義務付けている状況あり、今後室内空気の調湿や換気に伴う空調負荷の増大が予想される。このような背景のもとに、大量に賦存する低温排熱の利用、省エネルギー促進そして室内空気環境の快適性志向をカバーする環境親和型熱技術（グリーンサーモテクノロジー）の最右翼である熱サイクル機器として、吸着剤を用いた吸着熱式冷凍機やヒートポンプそして調湿機やデシカントクーリング機器等がある。吸着剤を用いたヒートサイクルは、古くて新しい技術で、環境に優しい技術と言うことで米国や欧州等で開発普及が進んでおり、我が国の代替冷媒を用いた蒸気圧縮機型冷凍機の展開と対比するものである。これら吸着剤を用いた空調関連の調湿や調温利用以外に、吸着剤の水蒸気の吸着及び脱着過程において、水分の蒸発・凝縮潜熱に相当する多量の熱授受があることから、吸着剤は蓄熱材として利用の可能性がある。特に高温多湿な我が国の気候環境においては、湿り空気中の水蒸気を吸着剤に吸着（除湿）する際に発生する吸着熱（放熱）を暖房熱源等へ利用し、その脱着再生（加湿）においては排熱や太陽熱等を利用する、いわゆる化学蓄熱の構築が可能となる。従って、本基礎研究は、一般に普及している低温脱着が可能なシリカゲル吸着剤を蓄熱剤として利用することを前提として、まず冷却による平衡状態に至る吸着特性向上を数値計算で検討するものである。対象とする吸着系は、球状吸着剤を充填した矩形充填層に湿り空気を流動させるもので、吸着性能向上特性は矩形充填層側壁からの冷却による効果を種々の因子（冷却温度、湿り空気流入湿度、平均空気速度、球状吸着剤粒子直径や充填層の寸法）のもとで明らかにするものである。

"Water droplets forms spherical surface due to the surface tension, and changing the size of droplets can vary the radius. In this paper, the availability of a droplet as a lens was investigated by applying for laser processing. Silica glass was used as a workpiece. Defocused ArF excimer laser beam was irradiated to the glass with / without droplets respectively. As a result, the laser beam could be focused by the droplets and caused cracks inside of the glass not at the surface. Changing the size of the droplets and the wettability of the glass enables to control focal length. Aspheric droplets formed by varying the wettability of the glass surface spatially, can control the laser beam intensity distribution. Many small droplets on the glass surface condensed by cooling enables to reduce the threshold of the laser fluence to process and enhance the processing speed."

This paper deals with a rail vehicle the wheelset of which has a clearance in the rolling direction. Numerical simulation is employed directly considering the clearance, which exists in the spline between the wheel and the axle, to analyze the dynamic characteristics. Simulation results show that the existence of clearance makes the wheelset rolling vibrate in a limit cycle oscillation. Then, generation mechanism of the limit cycle is investigated as well as the influence of the expanded clearance, which is due to the wear and deformation by long-term use, on the limit cycle. Moreover, it is shown that the use of higher equivalent conicity of wheel tread is desirable to reduce the flange contact by the limit cycle oscillation under existence of track irregularities.

This paper has dealt with the natural convection heat transfer of the microcapsule slurry composed of phase change material (PCM) as a latent heat storage substance. A rectangular cavity with two opposing heating and cooling vertical walls was selected as the present research model. The temperature difference between heating and cooling walls, the width of the cavity and the PCM concentration were set as parameters of natural convection heat transfer. The heat transfer coefficient of heating and cooling wall, the flow velocity profile and the temperature distribution of the microcapsule slurry were calculated by numerical computation. It was clarified that the transportation of latent heat evolved by melting and solidifying of the PCM in the slurry exerted on a strong influence on the natural convection heat transfer. Moreover, it was found that the heat transfer coefficient reached at the local maximal value with an increase in temperature difference between heating and cooling walls. In addition, Nusselt number was influenced by the transportation effect of latent heat that was caused by melting and solidifying of the PCM. The numerical results revealed quantitatively that the natural convection heat transfer depended on the PCM concentration, temperature difference between heating and cooling walls, and width of the rectangular cavity., 近年、熱エネルギー有効利用を目的とした潜熱蓄熱システムに注目が集まっており、さまざまな蓄熱材が開発されている。中でも、潜熱体融点温度以下の状態においても、常に流動性を維持する潜熱マイクロカプセルスラリーや潜熱マイクロエマルジョンといった潜熱物質を含有する機能性熱媒体が蓄・放熱特性において有利であり有望視されている。このような潜熱体を分散媒中に分散混合させた機能性熱流体を蓄熱材として利用する場合には、加熱及び冷却時における自然対流挙動および熱伝達特性を把握しておくことが必要不可欠である。本研究は自然対流の基本的な形態の一つである垂直対抗加熱・冷却壁を有する矩形密閉容器に潜熱マイクロカプセルスラリーを充填した場合の自然対流挙動や熱伝達特性に影響を及ぼすスラリーの熱物性、潜熱量、そして容器寸法などの影響について数値解析により検討するものである。

In this study, the model for flame spread over solid fuel is investigated. To re-examine the analytical solution by de Ris, our experimental data on flame temperature and flame spread rate are used, which were obtained by the measurements of downward flame spread over filter paper sheets in uniform ambient atmosphere diluted with either N2 or Co2. In the analytical models, the assumption has been usually adopted that the reaction rate is infinite and steady state is achieved. Then, in our previous experiments, oxygen concentration was reduced at elevated temperature up to 150℃ to confirm the limitation of analytical solution. Results show that, when the oxygen concentration is relatively high, the agreement of flame spread rates of analytical solution and experimental data is observed. However, decrease of the oxygen concentration reduces the flame temperature, and makes the flame spread unstable at some points. In this case, the analytical model can not predict the flame spread. This is explained by the fact that the assumptions for infinite reaction rate and steady solution are invalid.

In this paper, a generalized interpolation-based lattice Boltzmann method (GILBM) is introduced. The standard lattice Boltzmann equation is transformed into generalized coordinates using metrics. The advection term of the transformed equation is discretized with sufficient spatial accuracy to suppress the numerical dissipation. Additionally, a wall boundary condition suitable for body-fitted grids and a non-reflecting outer boundary condition are introduced. With the present method, the flow around a complex geometry can be solved using structured grids. The three examples of, the cavity flow, the flow around a circular cylinder, and the flow around an airfoil are shown as validation of the method to a wide range of Reynolds number. The present results show good quantitative and qualitative agreement with other computational studies., 資料番号: AA0045948047, レポート番号: NAL SP-57

The coherent structure at high Reynolds number accompanied with the turbulence, which passed across a flat plate blade, was analyzed by the wind tunnel test. The span-wise correlation length related to the aero-acoustic sources has been assumed as a statistical experimental equation based on this structure; also this length has been applied as the scale of the source in the prediction theory of the turbulent noise generated from a fan. This parameter is commonly used in the prediction equation; nevertheless it is still unknown whether the momentum of the coherent structure is conserved at where of the developed boundary layer or the wake. In this paper, the 3-dimensional coherent structure of a flat plate blade in the wake is clarified as the following; the coherent structure to the span direction is formed by a cell of the Reynolds shear stress pv'w', and the pv'w' forms the standing wave in the wake, moreover, the standing wave forms structural aero-acoustic sources at the trailing edge side on the surface of a flat plate blade., 長崎大学工学部研究報告 Vol.33(60) p.9-17, 2003

[Abstract] It is known that small quantities of surfactant additives can greatly reduce the friction factors during the flow of a heat transfer medium. This is because the generation of turbulent vortices is suppressed by the formation of rod-like micelles, and the flow remains laminar in the high Reynolds number range. However, the values of the heat transfer coefficients decrease during flow laminarization. The research objective is to examine heat transfer enhancement effects by air injection. This paper presents an experimental investigation on the heat transfer and flow characteristics in an air-surfactant solution two-phase flow through a vertical tube. The air was injected through the porous metal. In this condition, the flow pattern of two-phase flow was bubbly flow which contains many fine bubbles in any flow rate. The bubble diameter was changed by using different types of porous metal. In every condition of air injection, heat transfer coefficients were enhanced drastically with air injection. However, the effects depend on the diameter of bubbles. The heat transfer coefficients was Increased as the diameter of bubbles decreases. This result means that the bulk concentration of rod-like micelles in a surfactant solution in bubbly flow was reduced because micelle was concentrated on the surface of bubbles.