The purpose of the present study is to investigate effects of rear-diffuser for upper-surface inclination in the rear of car models. The Ahmed body with variation of upper-surface inclination angle α in the rear is used as a trial model, where variation of lower-surface inclination angle γ of the rear diffuser is constructed. The wind-tunnel experiments have been carried out with a moving belt to measure the lift and drag coefficients. As the result, 1) at any α, for variation of γ the lift coefficients decrease with minimum value at γ=20° and rapidly increase for γ>20°, and 2) at any γ, the lift coefficients decrease as α is made smaller. Flow visualization by the tuft grid, five-hole Pitot tube, and oil flows suggested the causes of lift reduction for the former that the wind from the lower surface is straightened by the rear diffuser and for the latter that the flow from the upper body interferes with the flow from the lower body.

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The delta-type wicker is an aerodynamic device for lift reduction, and the present study aims to investigate quantitatively aerodynamic characteristics of a car model with a delta-type wicker by wind-tunnel experiments. As the results, as the delta-type wicker is made higher, the down force (negative lift) is increased, but at the same time the drag is also increased When using the wicker together with a wing, however, the down force is further enhanced and the drag is restrained, compared with the case without a wing. The reason is considered that the wing suppresses the longitudinal vortices on the trunk deck and changes the wake to upward direction.

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The purpose of the present study is to improve the aerodynamic performance of a road vehicle by deflectors and splitters. The wind tunnel experiments have been carried out with a moving belt for a 1/5scale car model. As results, deflectors reduced the drag by 32% and splitters reduced the drag by 33%, compared with the normal model without them, and combination of deflectors and splitters reduced the drag by 38%. Furthermore, flow visualization by oilflows showed the factors of drag reduction that airflows avoid direct impingement against the tires by influence of deflectors and splitters

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When we take account of the environment surrounding, the development of vehicle with low energy consumption is required. Under these conditions the solar car races which develop the better performance energy are held. In these races, the factors which decide the winner are how the air resistance can be reduced. In addition, since vehicles for a solar car race are a lightweight vehicle, crosswind stability of the vehicle is important.

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Boundary layer transition is one of the most important phenomena to reduce aerodynamic drag. In JAXA, aFJR project has started from 2013. In this project, it is one of the important research task that expanding laminar boundary layer region on fan rotor blades surface to improve aerodynamic efficiency of fans. To realize that, prediction of boundary layer transition by CFD is important. Flow angle in boundary layer on rotor blades surface is sometime different from that of main flow (outside of boundary layer). This situation, called as crossflow, induces boundary layer transition. The transition induced by crossflow is important to design high aerodynamic efficiency fan rotor blades. We develop a turbulence model to predict transition induced by crossflow. In this paper, we adopted three shapes of nose cone for Supersonic Transport (SST) to verify our turbulence model. Numerical results have been compared with those in experiments. From the results, it was confirmed that the prediction accuracy of our turbulent model depends on the nose cone shape.

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Wind tunnel tests of flows around a railway vehicle were conducted to investigate unsteady vehicle underfloor flows. Numerical simulations conducted in the past indicated that pressure fluctuations observed on the side surface of the train were caused by these underfloor flows, which could cause flow-induced vibrations of high-speed trains affecting their riding comfort. The object of this research is to execute an experiment to validate the numerical simulation. The results of this study demonstrated that large lateral velocity fluctuations were generated in the underfloor of a train and that the previous numerical simulations were valid.

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An unvented tunnel entrance hood whose effect is equivalent to a vented tunnel entrance hood with open windows distributed along its length is proposed. The vented hood is a principal countermeasure for reducing the micro-pressure wave, and it can reduce effectively the micro-pressure wave by the suitable distribution of its open windows. Because the optimized windows distribution depends on the train nose shape and the train speed, it is necessary to readjust the distribution when the train speed increases or the new type train put into operation. Here, the influence of the cross-sectional area of hood on the effect of reducing the micro-pressure wave is investigated, and the suitable cross-sectional area of the unvented hood, which does not need to be readjusted and its effect is equivalent to the conventionalvented hood with windows, is estimated by the analytical calculation and the model experiments.

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For ensuring the stable train operation, it is important to estimate accurately the aerodynamic forces acting on a train vehicle. In this study, the aerodynamic forces acting on a vehicle model standing on a coast configuration model were measured by wind tunnel experiments. The coast configuration model consists of an embankment on a windward side and a cutting on a leeward side. The coast configuration model was so prepared that the cutting height, the gradient of slope of the cutting and the distance from the vehicle to the cutting can be varied. The aerodynamic forces acting on the vehicle model standing on the coast configuration model were compared with the aerodynamic forces acting on vehicle standing on the normal embankment. The aerodynamic force coefficients were smaller as the cutting was higher, steeper and nearer the vehicle. This showed the possibility that the cutting reduced aerodynamic forces acting on vehicle standing on the coast configuration than that acting on vehicle standing on normal embankment.

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In recent years, there are many researches about aerodynamic characteristics on the various cross sectional shape of the bluff body. For example, the shapes of edges of square cylinder are splay, roundish and cutout edges. It is known that the drag force of these cylinders reduce compared with the normal square cylinder. The purpose of this research is to clarify the aerodynamic characteristics of the square cylinder with the concave shape. The drag is measured by using wind tunnel experiment. The concave shapes are made by acrylic plates which are affixed on the both sides of the square cylinder. The acrylic plate has 3mm thickness. The lengths of the concave are 3, 6, 9mm respectively. The concave is attached in the front or rear of the square cylinder. As a result, the drag coefficient decreases as the length of the concave increases. The drag reduction of the square cylinder with the front concave is lower than that with the rear concave. The square cylinder with the length of 9mm and the rear concave has the highest reduction rate of drag coefficient with 13.1%.

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The objective of this study is to experimentally investigate the effects of the orbital velocity on the boundary layer flow over a rotating disk under orbital motion. The disk diameter is 300 mm, and the orbital radius is one third of the disk radius (50mm). The velocity field in the boundary layer flow is measured by the hot-wire anemometers. The effects on the transition Reynolds number from a laminar flow to a transition flow and the turbulent transition Reynolds number are shown by comparing the mean tangential velocity profiles. It is found by the frequency analysis of tangential velocity fluctuations that when the orbital velocity is more than +300 rpm, or when the ratio of the orbital velocity and the rotational velocity is 1/6 or more, in the case of coinciding rotating and orbiting direction, the generation of transient vortices is suppressed. However, in the case of the opposite direction, the transient vortices still exist even though the ratio of the orbital velocity and rotational velocity is 1/6 or more.

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We can affect various fields by studying the cylinder. We presents the results of the PIV in the boundary layer with a rotary cylinder put during the smooth flow. Unlike the boundary layer which developed on the fixed wall, it was revealed that a Gortler vortices developed in the boundary layer. In addition, I knew that a detachment position, a detachment shape and the shape of the whirlpool changed by the circumferential speed ratio, having ditch or not of the cylinder, a direction and a measurement section.

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High-speed rotation of various rotors such as motors for electric vehicles causes a problem that a windage loss increases significantly. Our group has proposed a self-evacuating pump with spiral grooves as a windage-loss-reduction method. It is important to maintain the gap between the rotor and the outer wall quite narrow such as 10 μm. In this study, an "Omusubi-shaped" floating bush is proposed to keep the gap narrow even under the condition that the rotor vibrated and thermally expanded. We examined the required gap value between bush and rotor which is necessary for a high-performance depressurization function. In order to demonstrate the feasibility of this method, we evaluated the levitation ability of the "Omusubi-shaped" floating bush.

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The flow generated by the rotation of the disk in a stationary cylindrical casing is investigated by the numerical approaches. In the flow around the rotating disk in the cylindrical casing, the normal and anomalous Taylor vortex occurs in the radial gap between the casing and the disk in particular conditions. When the normal vortex appears, jet-flows are exist between a upper cell and a lower cell. The anomalous Taylor vortex appears, beads-like vortices, ring-like vortices and polygonomical vortices are generated along the edge of the casing. The flow with steady Taylor vortices emerges in the radial gap at relatively low Reynolds numbers. At the higher Reynolds numbers, the turbulent Taylor vortices appear in the radial gap. We investigated steady, wavelet and turbulent vortices by the numerical analysis. According to the disk accelerate is increasing, flow instability is changed to more steady with same Reynolds number and same geometrical condition.

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A small hydropower generator harnessing the waters of a river, an agricultural waterway and city water services is a power plant that generates 1,000 kilowatts of electricity. A small hydropower generator using river water and agricultural water is inefficient, due to the restriction of flow resulting from fallen leaves and garbage. Using city water services takes advantage of a cleaner flow free of fallen leaves and garbage. In addition, the advantage of the small hydropower generator using city water services is that the rate of operation is higher than a photovoltaic power generator, which depends on daylight hours. The small hydroturbine is able to turn continuously, and it can generate electricity at all hours, but the output is smaller. The final aim is to generate electricity by setting up small hydroturbine in pipes of small internal diameters, like are present in city water services. This study is on the manufacture of a small hydroturbine and an analysis of the flow field with a high-speed camera.

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The present paper reports on an experimental study for underwater shock wave generation using high-pressure gas in order to trigger bubble motion in water. Shock waves are generated by an original diaphragmless shock tube. This shock tube produces a shock wave of Mach number 1.38 using an initial compressed air of 0.5 MPa in a driver section. A shock wave is discharged into an acrylic pipe provided with a silicone film. This acrylic pipe is set slightly above water surface. Excessive pressure and density increasing behind an incident shock wave have the silicone film rapidly deformed. Underwater shock waves are produced by impingement of a silicone film on water surface. Optical visualization is carried out using a high-speed camera, and a number of hemispherical underwater shock waves are observed with impact of the silicone film against the water surface. In addition, the impact velocity of the silicone film is considered to be over 20 m/s for generation of underwater shock waves.

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In order to investigate the shock wave modulation effect by the discharged plasma, the 2-dimensional CFD simulation was conducted. The results were also compared with the one-dimensional model which describes the shock wave through the temperature modulated field theoretically. The CFD result agrees with the theoretical model.

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The effect of the shock wave propagation Mach number and the discharged power on the shock wave modulation due to the discharged plasma was investigated experimentally. The shock wave acceleration and the shock wave attenuation was suggested with increasing the shock Mach number and the discharge power. In order to improve the measurement accuracy, the laser schrieren measurement system is newly developed.

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From a safety engineering viewpoint, it is important to predict the motion of flying fragments generated during accidental explosions. In our previous work, a special shock tube system to study the shock-induced motion of a solid body suspended in the air was constructed, and then the shadowgraph images of the shock-induced motion of a solid body were acquired by using a high-speed camera. It was found from the previous work that the body's motion was affected by the flow between the body and the floor, and the initial attack angle of the solid body. In the present study, we have observed the shock-induced motion of a solid body with relatively large, initial attack angle by Schlieren photography technique. The present results show how the initial posture of the solid body and the flow field around the body influence the body's motion.

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With recent increase of cars, the noise problem is caused by the exhaust sounds generated from exhaust pipes, which consist of weak pressure waves called blast waves. To diminish die noise, silencer is installed in front of the exhaust pipe. In the present study reflectors were installed in the high pressure portion of the shock tube to generate blast waves, and six types of expansion region were presented, combined with acoustic materials (glass wool). The pressure decay was investigated by transmitting factor and reflection factor of the incident blast wave, together with pressure sensors and high-speed movies by the Schlieren method As results, it was confirmed that acoustic materials greatly contribute to attenuation of blast waves: the one stage expansion model with glass wool shows the highest decay of the peak over pressure for transmission, and other models with glass wool show the second highest. They also contribute to decay of reflected shock waves propagating toward the upstream tube.

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In this report, we show CFD analysis around a two-step collector on a wind tunnel. Although previous study showed that the two-step collector is effective for pulsation suppression on circular wind tunnels, its mechanism should be realized for optimal design. SCRYU/Tetra^[○!R] was adopted for a CFD analysis tool and the turbulence model was DES. The equivalent diameter of nozzle in the analytical model was 4.3 m and the mean velocity of the jet was set to 27.8 m/s. The analytical results show the difference of vortex movement between a two-step collector and a usual collector. The vortex didn't influence inside of the two-step collector, though the vortex run into the usual collector. Furthermore, the velocity fluctuation in the two-step collector was smaller than it in the usual collector. Then the pulsation is suppressed by the two-step collector.

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The experimental and numerical studies were performed to clarify the fundamental flow characteristics of a fan with forward-inclined multi-blades. A Sirocco fan and crossflow fan are rotated in the open space, i.e. without casing. The crossflow fan simulates a Sirocco fan with a closed inlet. Using fan's height is 115mm, the inlet and outlet radii are 160 and 180 mm, respectively. The inlet and outlet blade angles are 90 and 150 degrees, respectively. The impller includes 52 blades. The rotational frequency is set to 24 Hz. The radial velocity fluctuations at the impeller outlet are measured using a hot-wire anemometry. The experimental and numerical results show good agreements with respect to frequencies and cell numbers. The FFT spectra of the experimental and numerical results show two peaks in the Sirocco fan and one peak in the crossflow fan. The two- and three-cell oscillations occur for the Sirocco fan, and the one-cell for the crossflow fan.

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The two dimensional unsteady structure including the interaction between a normal shock and turbulent boundary layer in a transonic diffuser is quantitatively and qualitatively visualized using a high-speed Mach-Zehnder interferometry. The experiment has been performed over a range of operating pressure ratios from 1.4 to 1.6 where the free-stream Mach number just ahead of the normal shock is below around 1.3. The shock oscillatory characteristics in the diffuser are also investigated by a high-speed schlieren method. Streamwise static pressures on the diffuser side wall are measured and the time-mean flowfield in the diffuser is compared with that from the RANS equation with the k-ω SST turbulence model. The dominant frequency of the normal shock oscillation obtained from the Mach-Zehnder interferometry is quantitatively identical to that from the schlieren method.

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Preliminary experiments of Planar Doppler Velocimetry (PDV) have been carried out for the development of two-dimensional velocity measurements in shock containing jets. Experiments have been performed using an intermittent indraft supersonic wind tunnel including an axisymmetric convergent nozzle with an inner diameter of 10 mm at the exit. The PDV with seeding particles over a range of 0.5-1μm in diameter and Nd-YAG laser are used in velocity measurements in an underexpanded sonic jet issued. Furthermore the RANS simulation with k-ωSST turbulent model of the jet is conducted to confirm the validity of the experimental results. It is found that the centerline velocity distribution from the PDV is in good agreement with that of the numerical simulation.

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Effects of valve lifts on jet angles of fuel sprays from a fuel injector with an outward opening valve were studied. We previously developed a fuel spray simulation that combined an inner flow simulation in a fuel injector, a fuel breakup simulation near nozzle outlets, and an air/fuel mixture simulation. The fuel spray simulation was applied to study the effects of the valve lifts on jet angles of fuel sprays. The simulated results were validated with measure ones, and the jet angles quantitatively agreed well with measured ones. The jet angle near the nozzle outlet was determined by valve-surface taper angle y, and the jet angle in the air/fuel mixture region was done by the Re number.

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This paper describes a mission outline and a design concept of an Autonomous Underwater Vehicle (AUV) for monitoring marine ecosystem and physical microstructures. The key point of this AUV development is to build a monitoring platform with low vibration at slow cruising speed, because the main target of the monitoring is the plankton environment with physical microstructures i.e. turbulences. For this need, the vehicle will be equipped with a newly developed water jet propulsion system. To increase an efficiency of the propulsion system, a duct is mounted covering the outlet of the water jet. The experimental date and the predictions were compared for the future design of AUV.

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In this paper microwave heating a liquid rotated and stirred by paddle wings is investigated numerically. In order to feed electromagnetic energy into this rotating system directly, we proposed to use the rotating metal shaft as a coaxial antenna. A set of multiphysics equations representing this system was solved by using finite-element method. In the actual computation, commercial software, COMSOL Multiphysics, was utilized. This software enables us to simultaneously solve frequency domain Maxwell equations and time-dependent Navier-Stokes and heat-transfer equations. The flow and temperature fields were extensively visualized as a result of this investigation.

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Due to the current downsizing trend and improvement of cycle efficiency, the demand for the restriction in low flow rate becomes to be expected. In order to enhance the heat transfer in this region, an assessment of the tube geometry has been conducted for an effectiveness of saliences on inner surface. This salience promotes the starting of turbulence and encouragement of heat transfer under the laminar flow region. In the present paper, experimental measurement of convectional heat transfer of tube, where Re = 420 - 1670, has been carried out for 6 different saliences and two channel heights. The effect was evaluated with mean heat transfer coefficient overall obtained by transient measurement with thermos-couples. As a result, case D, which has 4 rows and symmetric small salience, and whose channel height is 0.9mm showed best performance. Furthermore, for case D, Numerical simulation is executed and continuous turbulence structure is seen.

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Cold spray can make a coating on a wide variety of mechanical parts by spraying solid particles accelerated by a high speed gas flow through a converging-diverging nozzle. In cold spray, the stagnation temperature upstream of nozzle throat is one of the most important parameters which governs the coating quality, however, accurate measurement of the stagnation temperature, in a two-phase gas-solid flow, is impractical using a conventional way, such as thermocouple. In this study, the stagnation temperature is estimated by gas dynamic method using the mass flow rate, the stagnation pressure, and the accuracy of the estimated values is discussed.

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When solid fuel particles are heated, injection of pyrolysis gas occurs. This study calculated drag and lift acting on a heated particle in a uniform flow field. OpenFOAM-2.3.1 was used for the calculation. A rigid sphere was placed in the center of a rectangular parallelepiped calculation domain. The calculation domain was divided into 24373 meshes or 198342 meshes. Velocity of surface outflow changed from 0 to velocity same as the mainstream. Temperature of the particle changed in the range of 300-800 K. A Reynolds number was changed by changing the kinematic viscosity. Validity of a calculation method to obtain drag was examined from the calculation result of drag acting on a particle with uniform outflow from the surface. It was revealed that drag and lift increased with increase in temperature. Friction lift markedly changed.

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In this paper,the heat transfer enhancement of the vortex generator is investigated by the numerical analysis using the STAR-CCM+ commercial software. Vortex generator is installed in a rectangular channel, the shape of the vortex generator are trapezoidal, triangular and rectangular. The analytical conditions, Reynolds number based on the trapezoidal fin height is 2500, Prandtl number of the fluid is 0.71. Performance of the vortex generator was evaluated by bulk mean temperature gradient and pressure gradient from the channel inlet to outlet. Three shapes of the effective vortex generator are compared and it has shown the relationship of the the vortex structure generated by the vortex generator and the Nusselt number.

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In this study, we studied the heat transfer and fluid characteristics of vertical rectangular channel having grooved pattern; used as solar heat collection wall device, on conditions of natural and forced convection. A vertical rectangular channel (H=785mm, W=672mm) was used and the heat flux (100,200,300,400W/m^2) was given to the wall. Sheathed thermocouples were set at 8mm above on the inner wall, and at height from inlet z = 40, 372.5, 745mm to measure gas temperature, and they were also set under inlet to measure room temperature. On the condition of forced convection, the air was blown into only center channel and the average velocity was set to 0.18m/s at an inlet. On the condition of natural convection, the average velocity of air was measured using PIV system. On the forced convection, the velocity was estimated using the hot wire anemometer and the velocity profiles measured by PIV system. The heat transfer rate was calculated by the equation; Q=CpVp(T_<out>-T_<in>) {Q ; heat transfer rate [W], Cp; Specific heat at constant pressure [J/(kg・K)], V; Outlet volumetric flow [m^3/s], ρ; Density of air (293K) [kg/m^3], Tout; outlet gas temperature (z =745mm) [K], T_<in>; room Temperature [K]} As the result, when the heat flux was between 300 W/m^2 and 400W/m^2, heat transfer rate on forced convection was increased for 17% and 26% compared with natural convection. It was found that the heat transfer was significantly improved using forced convection.

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Experimental investigation has been carried out on natural convection induced around heated horizontal square cylinders. Main concerns were the influence of inclination angle on the flow and heat transfer characteristics. The inclination angles from horizontal θ and the side lengths d were varied systematically as θ = 0, 15, 30, 45° and d = 10, 20, 30, 50 mm. The experiments were performed in the range of modified Raleigh numbers, Ra_d^*, from 2×10^5 to 1×10^9. The flows around the square cylinder and the surface temperatures were visualized with dye and liquid crystal thermometry, respectively. The result shows that the onset of three-dimensional separation is delayed with increasing the inclination angle. The local heat transfer coefficients were also measured. The results showed that the heat transfer of square cylinder is enhanced with increasing the inclination angle.

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The present paper deals with the longitudinal heat transportation by oscillatory flow in small grooved tubes. The heat transportation experiments were conducted for the grooved tubes fabricated by a 3D printer. The internal diameters of the contraction and expansion sections of the grooved tube were 2 and 4 mm, respectively. The lengths of the contraction and expansion sections were respectively 3.3 and 2.3 mm and the total length of the grooved tubes was around 165.7 mm. The frequency and stroke length of oscillatory flow were varied from 0.1 to 3.0 Hz and from 15 to 20 mm, respectively. As a result, the effective thermal diffusivity in a grooved tube reached a value 2.3 times greater than that of a straight tube when the frequency was higher than 0.5 Hz, whereas no significant effect was observed when the frequency was lower than 0.5 Hz.

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This research investigated the influence of partition on the heat transfer characteristics in the corners of the vertical heated plate and the inclined heated flat plate attached to its top end in open space using real-time holographic interferometry and laser sheet method. The partition was set parallel to the vertical plate. The interval between the vertical plate and partition was varied from 5mm to 70mm. Then, the gap between the top of partition and the inclined plate was varied from 20mm to 40mm. The experiment was made at the angle of the corner 60° and the surface temperature of two plates 70℃. As a result, it was found that heat transfer at the corner may be increased under certain specific conditions between partition and the circulating flow produced by interference of upward flow along each plate

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The main object of this study is to grasp the heat transfer characteristics of the flow over a backward-facing step in a rectangular duct having side walls. In this experiment, distribution of the local heat transfer coefficient on the bottom wall was measured. The duct tasted has 15 mm height and 240 mm width at the inlet. The aspect ratio and the expansion ratio of the stepped duct were 16 and 2, respectively. Temperature measurement of the wall downstream the step was done using thermo-sensitive liquid crystal method. Reynolds number based on the step height was changed from 200 to 1000 as a parameter. Local heat transfer changes not only in the streamwise direction but also in the spanwise direction. The maximum heat transfer coefficient always appears near sidewall at each Reynolds number due to the downwash flow from the step near the side wall. When the Reynolds number is low, the ratio of the maximum heat transfer coefficient of the entire duct to the maximum one at the center of the duct becomes high. As the Reynolds number increases, the location of the maximum heat transfer coefficient at the center of the duct moves to downstream from Re=200 to 400 and moves to upstream from Re=400 to 1000. This tendency is the same as the behavior of the reattachment point. It was also found that the maximum heat transfer coefficient occurs more downstream than the reattachment point at each Reynolds number.

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Buoyancy and Marangoni convections were analysed both experimentally and theoretically. We investigated two-dimensional natural convection in a horizontal layer of incompressible fluid. 10 [cs] and 100 [cs] silicone oils were used as the test fluids (1 [cs] = 1×10^<-6> [m^2/s]). The temperature and velocity fields were visualized using liquid crystal capsules. The government equations of buoyancy and Marangoni convections were solved by the finite difference method. The numerical calculation agreed with the experimental result.

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Thermo-graphical method, Mach-Zehnder interferometer method, temperature-sensitive liquid crystal and so on could be given as representative examples for the visualization method of flowing gas temperature field. In these methods, however, high setup costs and/or hard-to-use operational skills are usually required. Therefore, when it comes to obtaining an approximate gas temperature field simply and quickly, those kinds of methods are not necessarily suitable. To overcome this problem, the authors have proposed a simple visualization method by combining a mesh screen and infrared thermograph, and have examined relation between aperture ratio and apparent emissivity of the mesh screen. In this study, the proposed simple method has been applied to the natural convection around heated vertical plate, and from experimental results, its availability has been shown. To use this method as a simple practical visualization tool, however, the effects of thermal conductivity of the mesh screen, heat transfer between the heated plate surface and the mesh screen on the temperature field, and the installation effect of the mesh screen on the flow field and so on have to be clarified in a quantitative way.

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It is necessary to predict the flow of hot gases generated by an emergency fire in a railway tunnel in order to establish a method for evacuation of passengers from the fire. Therefore, it is important to improve the precision of prediction. In this study, the results by three-dimensional large eddy simulation (LES) were compared to the experimental results of fire test in a full scale tunnel to verify the simulation accuracy. We calculated velocity, temperature and concentration of CO_2 by using the general-purpose fluid analysis software (Advance/FrontFlow/red Version 5.1). Calculations were performed under the condition of a compressible fluid and without consideration on radiative heat transfer. It is shown that a heat release rate or the heat transfer coefficient of air and a tunnel wall have a large effect on the behavior of the hot gases, while the thermal conductivity of a tunnel wall has little influence on the result.

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Influence of turbulence fluctuation of temperature and gas composition was examined based on absorption line database, in relation to the radiative heat flux toward the wall of large-scale industrial furnaces. Though some kinds of contrivance were included in the evaluation of radiative heat flux for relieving computation load, results obtained in this examination are equivalent to line-by-line analyses pursuing turbulence fluctuation. Combining our method about radiative heat flux with the governing equation solver for obtaining the spatial distribution of time-averaged values of velocity, temperature and so on, we can evaluate the heat flux both by radiative transfer and by turbulent transfer. As results, though the negligence of turbulence leads to obvious changes both in the distribution of radiative heat flux and in the spatial distribution of time-averaged temperature, influence on the total of wall heat flux is not so remarkable.

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The purpose of this study is to elucidate flame propagation behavior of homogeneous propane-air mixture under application of non-uniform electric fields. The non-uniform electric field was generated between the needle-shaped electrode and plate electrode, and a positive polarity single pulse high voltage was applied to the needle-shaped electrode (pulse width was 2 [ms]) and plate electrode was grounded. When the high voltage of 8 kV was applied, a thin air layer was effectively formed between the bottom of flame front and surface of plate electrode as the flame front approached to the plate electrode. This is because the induced current was generated in the flame front, so that the flame front and plate electrode repelled each other. The maximum combustion pressure was slightly higher than that of conventional combustion due to reduction of heat loss. However, when the high voltage was 16 kV, an electric discharge generated from the bottom of flame front, therefore the high voltage of 16 kV was too high and was not suitable to form the thin air layer. When a pulse width of 8 kV and/or 16 kV was more than 2 ms, the maximum combustion pressure lower than that of conventional combustion because the electrical potential was too strong and the flame front was deformed. The deformed flame front early reached to plate electrode and the heat loss was increased. Therefore, in this experiment, the single pulse non-uniform electric field of 2 ms width was the most desirable for formation of a thin air layer.

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The purpose of this study is to develop an ultra-micro annular type combustor that uses two types of coaxial cylindrical flames, rich premixed flame and diffusion flame. The combustor consists of inner and outer porous tubes, and rich C_3H_8-air mixture and air issued, respectively, through the inner tube outwardly and through the outer tube inwardly, forming a cylindrical stagnation plane sandwiched by the inner rich premixed flame and the outer diffusion flame. Petal type flame was also observed in the downstream of the cylindrical flames. Keeping the equivalence ratio φ_i and flow rate q_i of the rich mixture constant, an overall equivalence ratio φ_<all> is controlled by varying the air flow rate q_a of the outer tube. As a result, the minimum values of exergy loss and heat loss rates were found to be 0.57 and 0.31 respectively.

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This paper presents a numerical simulation study of the supersonic combustion at Mach number 2.48. Hydrogen fuel is injected into a combustor at sonic speed from the rear of hyper-mixer strut that can generate streamwise vortices. Although, for equivalence ratio 0.4, hydrogen is well consumed, it remains partly as unburned fuel for equivalence ratio 1.0. The property shows that the amount of combustion is saturated at equivalence ratios over 0.4, although there is a slight increase beyond 1.

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One-dimensional integral model for the non-uniform scalar variable profile with low frequency equivalence ratio oscillation has been developed. When the equivalence ratio of premixed mixture is oscillated, the gradient of fuel concentration in the upstream side of the reaction zone and of temperature gradinet in the downstream side of the reaction zone varies. It results in the additional fuen and het transfer to/from the reaction zone by the molecular diffusion of fuel and heat. When excess fuel is supplied from the upstream side and the excess heat is supplied from the downstream side, the flame is intensified. On the other hand, the flame is weakened when the fuel and heat are lost from the flame zone. When one is supplyed and the other is lost, both effects are canceled each other and no variation occurs at the flame zone. These results indicates that the equivalence ratio oscillation of premixed mixture plays an important role for the premixed flame dynamics.

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Experiments have been carried out to examine the performance of radiation cooing by new radiation materials, which is produced by mixing the very fine polar crystal metals into the high efficiency heat radiation paints. This concept is caused by increase of the surface area due to the rough surface generated by nano-size polar crystal metals. The best choice of mixing ratio between polar crystal powder and the radiation paints is 33.3% in weight. The results obtained show that the radiation effect of new radiation materials developed in the study is superior to those of existent radiation paints such as high efficiency heat radiation paints.

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We have developed the new energy saving technique using the electro-magnetic wave in the regime of far infrared rays. The technique is named as spectrum heat absorption method, which is achieved by the absorption of CO_2 spectrum emitted from the combustion exhaust gas through the radiation materials composed of very fine polar crystal metals. The technique makes it possible to accelerate the temperature exchange efficiency at the heat exchange region. The results demonstrate that the energy saving rate obtained from the technique is greater than 10% in house boiler used in agriculture field.

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We devised the Subchannel void sensor (SCVS), which consists of 6-by-6 wire electrodes and 5-by-5 rod electrodes to acquire boiling two-phase flow dynamics in a 5-by-5 rod bundle at high-pressure and high-temperature conditions. SCVS can acquire a time series data of local void fraction at 32 points of central subchannel region and at 100 points of near rod surface regions. The experimental results exhibit the axial and cross-sectional distributions of void fraction, which are suitable to validate the CFD and subchannel codes.

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While electric vehicles (EV) have the advantage of emitting no carbon dioxide, their cruising distances are relatively short compared to vehicles with an internal combustion engine. That has often been pointed out as the primary reason that prevents EV from becoming popular. The use of EV during the winter in the cold region depletes the battery faster because of the use of a heater, making the cruising distances even shorter. Therefore, this research examined an alternative of using a combustion-type hot-water heater in place of a vehicle-mounted heater (PTC) to see how much improvement could be achieved in the interior environment as well as the cruising distance during the winter. The goals of our test were to obtain information on what kind of influence a hot-water type heater for the EV may have on the cruising distance and compare that with a heater using BDF, and also to assess what kind of problems a BDF heater may present us.

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Cryopreservation technique has attracted special attention from those interested in food shortage in near future. However, because plant is fundamentally preserved with living, it is said that cryopreservation of plant is very difficult. Therefore, the estimation of plant damage is very important under low temperature in order to develop the cryopreservation technique of plant. This research investigated the possibility of damage estimation to plant in terms of normalized difference vegetation index (hereafter NDVI). This research consisted of two experiments. First experiment measured NDVI change of plant (leaf) under room exposure for several days in order to understand the relationship between NDVI and plant damage. Second experiment measured NDVI change under the exposure of low temperature. As a result, it is clear that there is the possibility of damage estimation of plant using NDVI.

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Ice adhesion force to a cooling solid surface caused many troubles accompanied by larger economical loss. Thus, the methods to reduce ice adhesion force to the solid surface were studied from various viewpoints. However, most of those methods were based on surface modification of the solid. In this paper, paying attention to adsorption of hydrophobic group of surfactant molecular to a copper surface, pure water with much smaller surfactant was frozen on the copper surface at -5℃, after which it was clarified that addition of the surfactant caused decrease in the ice adhesion force from comparison with ice adhesion force without the surfactant.

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This study aims to investigate the melting behavior of the ice plate with a calcium chloride solution in a rectangular container. When the ice layer is melted by the calcium chloride solution, the ice layer melts while absorbing the latent heat of fusion, and both the concentration difference and the temperature difference occur in the aqueous solution. Consequently, it occurs double diffusive convection, the melting behavior is expected to be complex. In this study, the melting behaviors in the case where the initial temperature of the ice layer and the aqueous solution is uniform, have been examined by three-dimensional numerical calculation. The effects of double diffusive convection on both the temperature and the concentration profiles in a rectangular container have been revealed from the present investigation.

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