In fusion welding, gravity makes molten metal flow downward and it sometimes causes an irregular-shaped weld bead and weld defects. This problem makes it difficult to conduct high-quality and high-deposition rate welding. To solve this problem, the authors propose an ECMP (Electromagnetic Controlled Molten Pool Welding Process) method which controls the molten metal flow by using an upward electromagnetic force. Based on this concept, the ECMP method has already been put into practical use for multipass welding of thick plates in horizontal and vertical positions in an LNG tank with a high-deposition rate. As to flat and overhead positions welding, the upward electromagnetic force can be acquired by adding the magnetic field and this upward force can lift the molten metal up under some restricted conditions, resulting in the remarkably improved shape of a penetration bead. Incidentally, although the conventional ECMP method has prevented molten metal from sagging downward using an upward electromagnetic force, the authors examine using a downward electromagnetic force in this study. Utilizing the downward electromagnetic force, improvement of the weld penetration in TIG welding processes of thick plates can be anticipated. In this paper, the authors investigate in detail the influence of the downward electromagnetic force on the flow and temperature of the molten pool.

SNCM630 is a material having particularly high strength among SNCM steels, and it is used for an engine member to be a connecting rod or a crank rod. Improvement of fatigue strength of materials is required, because the number of repetition stress quickly reaches the fatigue limit in the high-speed engine section. In this study, improvement of compressive residual stress on sample surface was investigated by applying ultrasonic wave to water jet cavitation (WJC) which is a technique of mechanical surface modification. Moreover, the authors compared it with conventional water jet cavitation (WJC) processing technology. WJC technology leads to the generation of high pressure when the cavities within the water collapse near the surface when a water jet ejected by a nozzle impacts a metal surface. This pressure causes a slight deformation of the impacted surface region and introduces compressive residual stress due to the elastic constraints of the underlying and surrounding metal. If ultrasonic irradiation is applied to WJC bubbles with diameters of several hundred microns, the bubbles are subjected to alternating high and low sound pressures, which leads to high pressures and a high-temperature reaction field. This technique is referred to as multifunction cavitation (MFC). Compressive residual stress was applied to each processed specimen surface. Moreover, improvement of corrosion resistance was observed in after MFC processing.

This work assessed the fundamental characteristics of multifunction cavitation (MFC), that was high-temperature and high-pressure cavitation, through both theoretical and experimental investigations. The application of ultrasonication to the floating cavitation of a water jet was found to produce microjets containing hot spots. MFC exhibited the capacity to perform nano-level hot work at a material surface, modifying the surface morphology and the surface electrochemical condition by hot spot melting. Ultrasonic irradiation of a water jet during floating cavitation was used to generate microjets with hot spots and this MFC process was employed to perform hot work on a Cr-Mo steel surface.

The improvement of fatigue life in inconel alloy by microshot peening was investigated. Shot peening is a widely used surface treatment method for improving fatigue life. This process imparts compressive residual stresses on the surface, thus improving the fatigue life of the machine parts. To reduce the surface roughness, the peening treatment with fine particles attracts attention. The size of the particle is very small and it is normal a one-tenth. In the peening process, the equipment were used an air-type machine. The microshot used were high-carbon cast steel and high hardness steel with an average diameter of 0.1 mm. The surface hardness data showed that work hardening extended deeper than the mean diameter of the media. In addition, when the workpiece was peened by high hardness steel powders, the surface hardness increased. The rotary bending fatigue tests were carried at a frequency of 3150 cycles/min. Improvement of the fatigue strength was observed by microshot peening. The higher effect was found in the peening by using high hard steel powders, because a work-hardened layer was formed deeper in the material.

To reduce the axial forging load in cold upsetting process, torsional oscillation was superposed with axial forging load. A cylindrical aluminum workpiece was simultaneously compressed with a maximum speed of 0.1 mm/s in z direction and twisted with a maximum angular speed of 0.5 rpm around the z-axis at room temperature. In case of the aluminum workpiece with an initial aspect ratio (height/diameter) of 1.0, a maximum reduction in the axial load was found to be approximately 80% for a rotation/compression speed of approximately over 300 °/mm.

The purpose of this study is to investigate the effect of initial microstructures on austenite (γ) formation behavior during intercritical annealing in high strength steel sheets. There are three kinds of specimens having different microstructures of hot-rolled sheets; specimen FP consisting of ferrite (α) and pearlite, specimen B consisting of bainite and specimen M consisting of martensite. The fraction of austenite in specimen M was larger than that in specimens FP and B below 730 °C, whereas that was in order of specimens FP > B > M above 740 °C. For specimens FP and B, martensite connecting along the rolling direction was observed. On the other hand, the distribution of martensite in specimen M was uniform compared to that in specimens FP and B. In the case of specimens FP and B, γ formation progressed by mainly local equilibrium during heating from 700 to 760 °C. In contrast, γ formation in specimen M progressed by paraequilibrium during heating from 700 to 730 °C, and that progressed by local equilibrium during heating from 740 to 760 °C. Therefore, we concluded that the kinetics of γ formation depends on initial microstructures in each specimen before annealing.

We electrochemically measured the polarization property of steel in bentonite. Geological disposal is the most realistic method in high-level radioactive waste in Japan. Long-term corrosion resistance is required for steel materials. As a waste container, a combination of carbon steel and bentonite has been proposed as one of the ideas for use. Therefore, it is necessary to characterize the corrosion of steel materials in bentonite. We compared sample in the difference of water rate in Bentonite.

Recently, the rare chemical elements, such as Ni and Mo, rises, so that it is difficult to use the stainless steel containing the elements. Therefore, “Lean Grade” stainless steel which are used Mn and N instead of Ni and Mo attracts attention. In the previous research, the studies were aimed at evaluating the corrosivity of Ni-high Mn-high N stainless steels comparing with the conventional stainless steels. As a result, the conclusion that the lean grade S2101” was excellent of the some duplex and austenite stainless steels, such as S2304, S31803 and SUS316L, in terms of corrosion resistance was obtained. In this study, the machinability and the expansibility of these materials are examined and the integrated evaluation is performed together with the corrosion-resistant result.
The results are obtained as follows: (1) Machinability of the lean grade S2101 and S2304 are almost equivalent to the low C austenite stainless steel SUS304L. (2) Processability of the super grade S31803 and S32750 are not good. (3) Machinability has strong correlation to the expansibility of some stainless steels. (4) Because the processability of Lean grade”S2101” is superior to the others stainless steels, it is possible to substitute S2101 for any austenitic stainless steel.

The formability of the laminated titanium sheet was investigated to control the ears in the deep drawn cup. Planar anisotropy causes ears to form in drawn cups. To control the occurrence of the ears, the deep drawing of the laminated sheet in consideration of anisotropy was carried out. In the experiment, the blank was pure titanium JIS1. The initial thickness and diameter of the sheet was 0.5 mm and 70 mm, respectively. The laminated sheet was constituted in two titanium sheets. Two sheets were located in the direction where varied in a rolling direction. Each sheet in stacked condition was not joined each other. Also please note that lubricant was not applied on the contact planes of sheets. In the deep drawing process, the laminated sheet was employed and a flat sheet blank was formed into a circle by a punch. A punch diameter is 40mm, and the drawing ratio is about 1.7. For the prevention of seizure in contact area between a drawing tool and titanium, titanium blank was treated by oxide coating. The clearance between the punch and die was set to be equal to the thickness of the laminated sheet. The lubricant used was the solid powders of molybdenum disulfide. The number of ears produced was four. The height of the ears decreased with increasing surface roughness. When it was located in the 45 degrees direction for a rolling direction, the ears of the drawn cup was controlled most.

In the Split-Hopkinson bar method, the duration of stress wave depends on the length of the striker. For the extension of the duration, therefore, the test equipment becomes huge because of long striker. In the previous study, it was attempted that the incident wave was prolonged by attaching an extended bar to the flange and connecting two stress waves. However, this device could not control the disturbance of stress wave due to the flange and the connection of the two tensile waves was not necessarily successful. Thus, in this research, analytical study was conducted on the connection method of two tensile waves by using a stepped bar model with the same mechanical impedance instead of the flange part. It was found that the disturbance generated in the center of the connected stress wave is smaller in our stepped bar model than in the flange model. It was also found that the cause of the disturbance occurring in the center of the connected stress wave is the vibration on the wave front of incident compression pulse propagating in the extended bar.

In this study, we investigate decay exponent of velocity intensity in grid turbulence by focusing on pressure drop at the turbulence-generating grid. In the present wind tunnel, we verify that the fluid acceleration of the freestream is sufficiently small, and it hardly affects decay characteristics of the grid turbulence. Also we show that the decay characteristics of the present grid turbulence agree well with those of the previous experiments. Using the present experimental apparatus, grid turbulence generated by two turbulence-generating grids is measured. By measuring not only decay coefficient of the grid turbulence but also the drag coefficient of the grids, we discuss the dependency of the decay coefficient on the drag coefficient.

To investigate the flow structure of the jet issuing from the pentagonal duct with and without the synthetic jet, the flow visualization was carried out. And the velocity measurements of the jet flow were performed by using the PIV method. The jet diffusion was investigated by analyzing the velocity distributions. In order to excite the share layer of the jet, the synthetic jet was spouted from the actuator set on the outside of a vertex of the duct exit at 45 degree angle with respect to flow direction. As a result, it has been found that the jet diffusion adding the synthetic jet in xOy -plane is promoted.

In this study, an experimental study is performed for multiple-passage duct flows. The multiple-passage is a reverse flow type, and consists of the five branch ducts. The duct flows are investigated from the view point of flow uniformity and pressure loss. Experiments are performed for the Reynolds number based on the bulk velocity and hydraulic diameter at the inlet duct from 6.0×10² to 1.5 ×10³. Aspect ratio (i.e., the ratio between the height and width of the branch duct) is changed into 0.6, 1.0 and 20. The effect of the outlet manifold volume on the flow distribution is investigated. The results show that the flow rate are hardly affected even if the aspect ratio changes. As the Reynolds number increases, the uniformity of the flow rate through each branch duct gets worse. The uniform flow distribution is realized by increasing the volume of the outlet manifold. The flow uniformity is related to the reduction of the recirculation region which exists at the inlet manifold.

The determination of energy losses caused by flow division at T-junctions is important in the design and analysis of industrial fluid transport systems. In this study, an experimental study is performed for dividing square duct flow in 90 degree T-junction with sharp and rounded corners. The Reynolds number Re based on the mean velocity and the hydraulic diameter ranges from 1.3 × 10³ to 1.8 × 10⁴.The flow rate ratio (i.e., the ratio between the branch and main duct flow rates) is set from 0.2 to 0.8. Duct width and height are fixed at 10 mm in the main and branch ducts. The wall static pressure and loss coefficient are measured to quantify the energy loss. The loss coefficient of the branch duct with sharp corner increases rapidly as increasing flow rate ratio. Rounding the corner reduces the pressure loss in the branching flow. These experimental data provide empirical loss coefficient equations for T-junctions, which constitute useful tools for the determination of loss coefficients for T-junction.

The present study performs three-dimensional numerical analysis on the heat transfer and the interactions between asymmetric hairpin vortices formed behind asymmetric hills which are arrayed alternately in a laminar boundary layer. Asymmetric hairpin vortices are periodically shed in the wakes formed behind hills, these vortices interact, and a high turbulent kinetic energy region is formed widely. As the shape of hills increases in asymmetry with respect to the spanwise direction, the high turbulence region further spreads. However, the rotation of the vortices is weakened, and the spatially averaged turbulence decreases. So, the heat transport is also weakened, the heat transfer rate decreases.

There are two types of square lattice structure, biplane grid and woven screen, in order to control various industrial flow fields. In particular, the square biplane grid which consists of several cylinders arrayed at right angle is often used to make turbulence. In addition, it is proposed to apply the heat transfer enhancement effect to heat exchanger. Accordingly, it is important to reveal the flow characteristics around circular cylinders forming biplane grid. However, the flow characteristics around circular cylinders forming square biplane grid has not been fully examined. Therefore, the aim of this study is to clarify the three-dimensional flow field around the circular cylinder members forming the square biplane grid by means of the measurement of surface pressure distributions, the estimation of local drag coefficients. It was found from this result that the difference in open area ratio affected the flow structure around square biplane grid forming by upstream and downstream circular cylinders.

It is necessary to reduce the particulate matter (PM) in the exhaust gas of internal combustion engines. In gasoline direct injection engines, a fuel has more probability to attach to the wall than in port fuel injection engines because the fuel is directly injected into the combustion chamber. Fuel wetting to the combustion chamber wall and injector tip generates deposits, which results in PM occurrence. Therefore, precise prediction of the spray formation is required. In this study, we investigated the effects of injector-valve motion, especially off-axis valve motion, on internal nozzle flow and spray shape using a numerical simulation method combining the volume of fluid method and discrete droplet model. The results are summarized as follows. (1) In the case of y-axis offset, which is the direction parallel to the symmetrical plane of hole location and geometry, the spray shape and footprint was more symmetrical than in the case of the non-offset because the flows near the hole inlet stabilized due to the off-axis valve motion. (2) In the case of y-axis offset, which is vertical to the symmetrical plane, asymmetrical footprint and spray shape was observed, which indicates that the off-axis valve motion in the asymmetrical direction effect the spray shape. Specifically, the sac inner flow at low valve lift exhibited larger velocity than that of high valve lift, which results in changing the spray-tip shape.

An experimental study investigated the influences of fuel nozzle shape on soot emission from co-flow propane-air diffusion flame. The cross sectional shape of the fuel nozzle is circular and square. Soot discharge rate, flame height, flame perimeter and flame temperature are measured. A numerical simulation was performed to evaluate non-reactive flow. Excess air ratio was varied by adjusting air flow rate with fuel flow rate kept constant. Soot was collected by a glass filter and then the filter was weighed to measure the mass of soot by an electric balance. The soot discharge rate is determined by dividing the mass of soot by suction time. The obtained results are summarized as follows: 1) As the excess air ratio decreased, the soot discharge rate for the square nozzle became lower than that for the circular nozzle. 2) The flame height for the square nozzle was lower than that for the circular nozzle. 3) The high temperature region at upstream part for the square nozzle developed wider than that for the circular nozzle. 4) In the vicinity of the corner of the square nozzle, the air flow velocity toward the fuel nozzle was higher than that of the circular nozzle. It is considered that the air flow near the corner promotes combustion reaction and suppresses soot emission.

This paper presents three-dimensional numerical analysis of gas-liquid interface instability in a shear flow. The present study investigates influences of two-dimensional disturbances on the interface instability. When only the streamwise disturbance is given on the interface, the pressure inside the liquid is low and high around the crest and valley of the interface due to the shear flow, respectively. As a result, the interface becomes unstable. The amplitude of the interface increases with time, and the rolling of the interface occurs. When the streamwise and spanwise disturbances are given on the interface, the growth of the interface becomes slow. The interface early grows in the case of the long wavelength of the spanwise disturbance. On the other hand, if the wavelength of the spanwise disturbance is shortened, the amplitude of the interface decreases with time since the influence of surface tension becomes strong due to the large curvature of the interface.

This paper presents the numerical analysis on interface instability of liquid ligament in shear flow. Due to the effect of shear flow, the interface of liquid ligament is unstable even in the wave number that does not grow in still gases. Moreover, the growth rate of ligament interface is greater than that in the still gases. The wave number at which the growth rate becomes maximum increases with increasing the velocity of shear flow. As the Reynolds number of liquid increases, the liquid ligament interface highly deforms, and then the pressure in the cross section at the neck of liquid ligament is increased. As a result, an axial velocity of the ligament increases, an equivalent diameter of the neck of ligament decreases more rapidly.

A novel droplet generator equipped with flow-control has been developed for the formation of various liquid droplets. Two fast falling droplets with small angle are collided in air and are formed one droplet, which gets out of its shape from various type of oval to ball in falling by convection inside a small droplet. Water and ethanol are used as two different falling liquids.

In the recent years, the strong oxidation power of ozone and radicals has been expected to be useful to water treatment. The purpose of the present study is to improve a micro-bubble generator with gas-liquid interface discharge for the application of water treatment. In the experiment, the decolorization test was conducted using indigo carmine solution as a sample in order to clearly the effect of supplied air volume and applied voltage on the oxidation decomposition. The results show that the decolorization of solution by the gas-liquid interface discharge in micro bubble was succeeded in about 2 hours. In addition, the decolorization processing speed became faster with increasing of supplied air volume and applied voltage.

We clarified experimentally that the airflow is stabilized by changing the stabilizer shape near the side walls from straight line to concentric circle in the room air conditioner indoor unit without decreasing the energy saving performance. Under both low air flow and high static pressure conditions, the stabilizer which proposed in this report tends to increase static pressure at the same flow rate. In addition, it reduces surging noise from the indoor unit outlet and reduces the fluctuation of the fan rotational speed. These characteristics become more prominent by extending the parts of concentric circles to the circumferential direction.

The noise reduction of the centrifugal blower is important problem for the working and the living enviromment. In this study, to investigate the noise in the small airflow region, we focused on the Blade-passing frequency(BPF) noise and carried out the experiment and the unsteady simulation of the flow in the blower. To clarify the cause that BPF noise occurs, we investigated the pressure fluctuation at the trailing edge of the blade and the generation mechanism. We also compared characteristics of the pressure fluctuation with those of the other airflow region. It was found that the pressure fluctuations obtained by the numerical simulation became large in the case of small and large airflow regions as well as the experimental results and the noise measurement, however the generation mechanisms of the pressure flactuation are different between the airflow regions.

To reveal the mechanism of a flying pipe, we conduct field observations of the flying pipe in rotation using a pair of high-speed video cameras, together with 3D motion analyses based on their recorded images. Moreover, we attempt numerical analyses. As a result, the field observations show the statics of flying-pipe aerodynamics for both commercial and simplified laboratory models. The numerical analyses reveal details of the flow around the flying pipe.

Die-casting, which is able to cast mass production by high speed and pressure casting, cause characteristic defects by trapping air in molten metal. In this investigation, a runner shape that was not influenced by the injection speed and was able to decrease blow holes was obtained in die casting. Mold filling processes of the aluminium casting, using two types of runner shape, the basic model and the claw model, was simulated with the JSCAST. A metal flow and bubbles positions were solved numerically by a three-dimensional numerical model, based on the direct finite difference method and the Volume of Fluid method for treating the free surface. The simulation results indicated that to change runner shape was considerably effective against air volume. In the basic model under even flow condition, bubbles are densely packed in the upper and lower portions of the cavity. However, air bubbles increase toward the upper part of the cavity under two steps condition. On the other hand, in the claw model under both conditions, massive bubbles were found in the upper part of the cavity, and it was confirmed that fine bubbles are distributed over a wide range. It was also confirmed that the amount of bubbles decreased by about 38.5% depending on the difference in injection conditions of the basic model, however the amount of bubbles was reduced by about 73.1% depending on the difference in shape. In other words, we confirmed that the mold method can reduce about 56.3% than the velocity method.

In order to realize the wind and hydro power generation by using flow-induced vibration, Multi-articulated flat plate was devised. Multi-articulated flat plate is constructed plural shafts and plates and it flutters very periodically in the uniform flow. The objective of this study is to clarify the fluttering characteristics of Multi-articulated flat plate. The fluttering frequencies of Multi-articulated flat plate were measured in various flow velocity by the wind tunnel experiments. Multi-articulated flat plates were tested in various dimensions and density. The fluttering frequencies were increased with increasing the uniform flow velocity and were discontinuously changed when the fluttering modes would be changed. From the results of the dimensional analisys, it was found that the Strouhal number of fluttering frequency depended on Reynolds number and mass ratio.

In this study, the propagation of the reaction front in the aqueous solutions of acetic acid (CH₃COOH) and sodium hydroxide (NaOH) has been investigated. First of all, we developed the measuring system of refractive index distribution using laser speckle method because of our objective. When the densities of CH₃COOH aq. and NaOH aq. were almost same, the mixing layer of CH₃COOH aq. and sodium acetate (CH₃COONa) aq. with relatively low density could be formed. Then the reaction front had small disturbances and big swell due to Rayleigh-Taylor instability. As time elapsed, the disturbances united and transformed to the large plumes. As the downward flows generated between the plumes, the configuration of the reaction front became more complex.

Influence of the external heating on the particle adhesion and specific charge in the fluidized bed has been investigated. The adhesion amount on an internal wall of the fluidized bed had a maximum value along the distance from the inlet up to T_S = 60°C. The specific charge increased with the heating temperature up to 60°C. On the other hand, the particles agglomerated at almost softening temperature (80°C) and then both the adhesion mass and the charge were lower than that at 20°C < T_S < 60℃. Dependence of the water content in the particles on the particle adhesion and specific charge in the fluidized bed has been also investigated. The initially humidified particles agglomerated due to the liquid bridge force and motion of them could be suppressed at T_S = 60°C. So that, the adhesion mass and the charge of the initially humidified particles were lower than that of the initially dried particles.

In this study, the temperature measurement of the DC discharged plasma has been conducted by an emission spectroscopy with the spectrum matching method. The calculation code which was developed by our group was used for the theoretical spectrum database construction for the spectrum matching method. The second positive band of the nitrogen molecule and the first negative band of the nitrogen molecular ion were under consideration as the electronic transitions in the present calculation. Before constructing the theoretical spectrum database, the verification has been conducted by the comparison between the calculated theoretical emission spectrum and the literature results. As a result, the calculated theoretical emission spectrum generally agrees the overall shape of the spectrum of the literature results. The temperature was determined from the measured spectrum by applying the spectrum matching method under the condition in the initial pressure 2 [kPa] for air as a test gas. As a result, the rotational temperature of N₂ was 1900 [K]. This temperature is valid from the view point of the comparison with the other experimental result using the similar experimental facility.

In this study, the temperature estimation method in the discharged field by using the shock wave propagation velocity was investigated. By using the visualization results for the shock wave propagation velocity measurement, we conducted the temperature estimation. For the case without the discharge, the estimation temperature was almost the initial temperature (~300K). On the other hand, in the case with the discharge, the higher temperature (~1000K) was estimated. Therefore, this temperature estimation method is promising method for the future temperature measurement method with some improvement.

Advanced oxidation processes (AOPs) are considered as a promising remediation technology for water treatment due to the fast decomposition rate and environmental friendly. Generally, the advanced oxidation processes refer to methods generating OH radicals in water for the decomposition of persistent organic pollutants. However, since the lifetime of OH radicals is considerably short, they need to be generated and react with other pollutants simultaneously in water or near the water surface. Discharges in multiphase environments such as discharges inside bubbles in liquids attract attentions for the easy discharges in a gas phase and the simultaneous diffusion of OH radicals from bubble to liquids through bubble interface just after generating. A discharged bubble jets system has been constructed to investigate the decomposition ability for acetic acid by generating OH radicals inside nanosecond pulse discharged bubbles. However, the complex generation and diffusion processes of chemical radicals are still unclear in the experiment. Therefore, the purpose of this research is to clarify the physicochemical factors which are favorable for the generation of OH radical in water by a discharged bubble. A two-dimensional plasma-liquid two-phase model for a nanosecond pulse discharged bubble is developed by considering chemical reactions in liquid phase as well as the diffusion from bubble to liquid. It is found that OH radicals can diffuse to only several micrometers in liquid from bubble interface and are most generated under low applied voltage and high frequency conditions.

The turbine gas inflow in a turbocharger exhibits pulsating behavior because of the opening and closing of engine valves. Turbocharger data for engine design is usually computed for steady flow conditions. However actual turbochargers operate under pulsating flow which is reported to decrease turbine efficiency. In this study, experimental investigation and Computational Fluid Dynamics (CFD) under pulsating flow condition were performed. Unsteady performance measurement and Particle Image Velocimetry (PIV) measurement were performed by using a model turbine test rig. RANS and DES were used. On the computational side, it was noted that DES is needed to simulate the flow pattern of a turbine outlet under pulsating flow.

The purpose of this research is to clarify the change of characteristics of aerodynamic drag and lift of a car by the engine loading system (engine arrangement) and the air inlet system (opening area and position) with and without a radiator in wind-tunnel experiments. A simplified car model with 1/5 scale is generated with reproduction of the engine room with the transparent acryl externals for visualization. In the wind-tunnel experiments, the moving-belt ground board is adopted to capture ground effects with force measurements by use of load cells. Flows are visualized and measured by a smoke method. As results, with enlargement of the opening area, the drag increased overall although depending largely on the engine loading system and the opening position, the front lift increased and the rear left decreased; the effect of the radiator was to relieve the change of the drag and lift.

In this paper, the water wave metamaterial is studied to realize the negative refractive index. Shallow water waves propagating to the water channel are analogized to electric waves flowing through the distributed constant circuit, and thus the circuit theory based approach is extended to water waves. We propose the design method of the water channel that characteristics of both inductance- and capacitance- equivalents are negative. We also derive that the refractive index and the phase velocity become negative values at that time. Water channels are periodically cascaded and consequently, the water channel network is constructed. The water channel network acts as the water wave metamaterial. The proposed theory is validated by the numerical computation and there is a good agreement between them. The numerical simulation shows that waves incident to the water channel network are refracted at the negative angle and the phase velocity propagates against the group velocity, that is, backward waves are observed.

It is known that sinusoidal leading edge is effective in low Reynolds number region. However, the effect of the wavelength and the amplitude of the sinusoidal leading edge on the wing performance has not been clarified yet. In this study, we carried out the wind tunnel experiment and numerical simulation to investigate the effect of the wavelength and the amplitude of sinusoidal leading edge on the wing performance. As a result, it was found that amplitude-to-wavelength ratio λ/A can be used to estimate the increase amount of the lift force in λ/A≦4, however, in λ/A≧4, the increase amount of the lift differs depending on the changing parameter.

Drive is the most common ball type of table tennis1, but there is a high-bouncing general drive and a low-bouncing drive. In order to clarify the mechanism of the latter drive, we used a table tennis machine and a digital camera (960 frames per second), and examined changes in the angle, rotation number, and velocity speed of the ball before and after the ground contact. As a result, it was found that a ball with a large number of revolutions before the ground contact does not bounce greatly, part of the rotational energy is converted into velocity energy, and it becomes a low-bouncing and fast drive.

In order to clarify the frequency response characteristics of a lean methane-air premixed flame to sinusoidal equivalence ratio oscillation, we developed a new burner with a wall-stagnating flow that allowed measurement of the flow field by using particle image velocimetry (PIV). To create fluctuations in the equivalence ratio only in the direction of flow without varying the velocity field, fuel and air flow rates were controlled by alternately vibrating two sets of speakers. Fluctuation frequency f ranged from 5 to 50 Hz. Following results were obtained: (1) The oscillation amplitude of flame position of dynamic flame took an approximately constant value at beginning with respect to the increase of f, and then decreased. (2) At f > 20 Hz, the oscillation amplitude of burning velocity of dynamic flame became greater than that of the static flame, over the same equivalence ratio fluctuation range. This means that when the flame moves against (along) the fuel flow, the mass flux at the flame front increases (decreases) as compared with that of the steady flame.

In this study, the relationship between the nanoparticle formation during premixed flame at high oxygen concentration and the temperature has been investigated when the molar fraction of oxygen X_O2 changed from 0.28 to 0.40. We produced a silica dioxide nanoparticles by the chemical flame method. We use a methane for fuel and air and oxygen for oxidizer. In addition, hexamethyldisiloxane was used as a particle precursor. For X_O2 = 0.28, as the particle size decreased firstly with the distance from the burner exit, the particle formation process could be controlled by the surface reaction below the melting point of SiO₂. Secondary it could be controlled by melting and densification of the particle when the temperature was higher than the melting point. On the other hand, for X_O2 = 0.40, the controlling step of the melting and densification appeared faster than that for X_O2 = 0.28 because the temperature was higher than that for X_O2 = 0.28. After that, the primary particle size increased with the distance from the burner exit because the particle formation could be controlled by surface reaction on the particle.

Effects of ambient oxygen concentration and ambient density on combustion of diesel spray under high temperature and high pressure ambient were experimentally examined using a constant volume combustion chamber of 60cc that simulates the combustion chamber of automobile diesel engine. The heat release rate was calculated from combustion pressure using a pressure gauge. The KL factor was quantified through an image analysis technique using two-color method. The values of ambient density and oxygen concentration were changed from 10kg/m³ to 15kg/m³ and 13% to 21%. It is confirmed that the ambient oxygen concentration and density has large effect on the shape of heat release rate and the total KL factor. As the decrease of ambient oxygen concentration and as the decrease of ambient density, the heat release rate decreases and total KL factor increases. In comparing with heat release rate and total KL factor, the peak of total KL factor was located in after burning period in the case of low ambient oxygen concentration.

Bioethanol is well known that the oil-alternate fuel for automobiles as carbon neutral fuel adapted to environmental problem. Furthermore, ethanol water solution is thought effective to depletion problems of fossil fuel resources. The research so far shows that continuous combustion is archived in a wide range of air ratios using low concentration ethanol water solution. This study aims to examine that the influences on spray combustion characteristics by using a swirl burner. The exhaust gases and combustion temperature are measured in combustion chamber and exhaust pipe by using K type thermocouples. The main conclusions are as follows: 1) The combustion temperature decreases with increasing the air ratio for the ethanol water solution. 2) It is possible to achieve the over 90% combustion efficiency at the low concentration for ethanol water concentration(E45). 3) The CO emission decreases with increasing the air ratio at the low concentration for ethanol water concentration(E45). 4) The NOx emission decreases with decreasing the ratio of ethanol addition at any air ratios.

An attempt to develop a scale model to estimate extinction limits of spreading flame over electric wires in opposed flow under microgravity has been made. Ethylene tetrafluoroethylene (ETFE) insulated copper (Cu) wire is chosen as the sample wire because of the availability of its experimental data. The results showed that the estimated extinction limits given by the scale model developed in the present work corresponded well with experimental results qualitatively. However, further modifications of individual sub-models are expected to provide quantitative estimation.

It is needed to greatly modify fuel component because of strengthened sulfur component regulations in fuel oil for ships by IMO (International Maritime Organization). Light Cycle Oil (LCO) which contains less sulfur component has been focused as a base fuel. The increase of the LCO mixing ratio in fuels for diesel engines is expected in the future. Evaporation characteristics which are one of a physical process in spray combustion affect flame stabilities and combustion emissions. The objective of this study is to clarify the relationships between evaporation characteristics and fuel characteristics of LCO by conducting evaporation experiments of LCO. The evaporation experiments of LCO were conducted by single LCO droplets at various ambient temperatures (473~873 K) and pressures (0.1, 0.5, 1.0 MPa). Moreover, the evaporation characteristics of 5 types LCO were compared to clarify how the fuel properties affect the evaporation characteristics. As a result, it was found that the difference of the droplet lifetimes between fuels is large at low ambient temperature. This is because high boiling components in LCO make the droplet lifetimes of LCO longer from the middle to the late of evaporation. The pressure dependence of evaporation coefficient of some LCO at high ambient temperature was different from that of single component fuel. This is possibly caused by effect of multicomponent of LCO on the behavior of the evaporation coefficients.