Large-eddy simulations of the separated flow over NACA0006, NACA0012 and NACA0015 airfoils, which are controlled by a DBD plasma actuator, are conducted to investigate the effect of airfoil configuration on separation control. In these simulations, position and operation conditions of a DBD plasma actuator, such as the burst frequency, the degree of induced flow, are varied as simulation parameters. It is clarified that the control effects are different from each airfoil even if same numerical parameters are used. Effective position of actuator is near separation point to suppress the separation for all airfoils. The effects of separation control become smaller for cases with larger separation regions, and the separation development significantly influence on the control.

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Vortex generator(VG) is one of the most successful flow control devices. A conventional VG is a passive control device; it does not adapt various velocity conditions. As an alternative to the conventional VG, we propose to use a plasma actuator(PA) as a VG. Since few studies have been made on such a vortex generator-type plasma actuator(VG-PA), many questions still remain open, e.g. , the mechanism of vortex generation and the magnitude of generated vortex. In the present study, we experimentally characterize and evaluate a VG-PA and examine the effect of burst mode. We also apply this VG-PA for suppression of vortex shedding from a panhead of used for high-speed trains. The present experiment shows that a VG-PA generates a distinct vortex and that flow separation around a panhead can be delayed by using VG-PA. It is also shown that a VG-PA operated in the burst mode works differently as compared to that in the continuous mode.

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Development of the optimization system for aerodynamics control using plasma actuator has been conducted. The system which uses the Efficient Global Optimization method was designed to explore the optimum value with a small number of sampling. By using the current optimization system, the Lift maximization for bluff body using plasma actuator, with multiple design variables, was successfully carried out. The results of experiment that indicates the optimization method developed in this study is evaluated as effective and can reduce a numerous number of sampling during wind-tunnel experiment.

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Present paper investigated control of separated flow over an NACA0015 airfoil by a single dielectric barrier discharge(DBD) plasma actuator installed at the leading edge using large-eddy simulations with high-order accurate and high-resolution numerical scheme. A chord-based Reynolds number of 260,000 and an angle of attack of 18.8 degrees were considered. A phenomenological DBD plasma actuator model was employed to provide the spatial body force distribution. The unsteady operation so-called a burst mode actuation was introduced and two burst frequencies of 1 and 6 with constant burst ratio of 0. 1 were analyzed. Results showed that the DBD plasma actuator could change dynamic behavior of shear layer separated from the leading edge and lead to reattachment near the leading edge when the actuation with burst frequency of 6. However, it was not able to lead to fully attached flow on the upper surface of the wing due to the adverse pressure gradient. Lastly improvement of time-averaged aerodynamic performance attained by flow control was also discussed.

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This study is concerned with the flow control around airfoil when a dielectric barrier discharge(DBD) plasma actuator is mounted on the leading edge. Lift force and velocity field around the airfoil are measured for the on and off modes of the plasma(pulse modulated drive). As a result, the behavior of the variation in the lift force is different depending on the modulation frequency. Over the angle of maximum lift, there is the most effective driving time period to avoid decreasing the lift force, and the strong vortex structure are formed in the shear layer.

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About the flow around an airfoil, it has been known that flow separation occur behind it. And we have used various actuators such as riblet and vortex generator to control the flow. But these actuators have some drawbacks, for example they have complex structure, noise and low energy efficiency. Recently, as an alternative of these actuators, active controlling devices such as DBD(Dielectric Barrier Discharge) Plasma Actuator have been studied, which can overcome some drawbacks mentioned above. The purpose of this study is to suppress flow separation around the airfoil with DBD Plasma Actuator by generating longitudinal vortex and to confirm the effect of drag reduction acting on airfoil. The experiments were conducted into wind tunnel at constant temperature. The airfoil type is NACA0021. The flow velocity is measured with a Constant Temperature hot-wire Anemometer(CTA), pitot tube and precision micro manometer. The mainstream velocity is 1.8[m/s], Reynolds number is 10000, angle of attack is 12[deg], applied voltage is 5.0[kV], applied frequency is 4.0[kHz]. It was found that the longitudinal vortex generated by DBD Plasma Actuator enabled suppression of separation around the airfoil. The maximum drag reduction rate was about 9[%].

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In nature, flight organisms change flow field around the wing and produce fluid force according to flapping motion of flight organism wing. Therefore, the flow field around the flight organism wing and fluid force are remarked academically. We clarified a vortex ring generated over a butterfly wing in downward and upward flapping motion using PIV measurement. We estimated the dynamic lift from the circulation of a vortex ring generated over a butterfly wing. After that, we measured the dynamic lift to verify the estimation result. The estimation and measurement result are almost same in downward flapping motion. However, estimation result of dynamic lift doesn't correspond to the measurement result of dynamic lift. The reason is that we just evaluated a vortex ring over the butterfly wing but we didn't evaluate a vortex ring generated wake field of the butterfly. So we estimated the dynamic lift using the vortex ring over a butterfly wing and wake field of the butterfly. Therefore, we clarified that estimation result of dynamic lift correspond to the measurement result of dynamic lift.

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There has been considerable research on unsteady rigid airfoils that are different configuration and thickness. However, dynamic fluid forces and flow fields about moving elastic airfoils have not been understood. Because, these flow fields around moving elastic bodies are treated as fluid-structure interaction(FSI), and increase considerable parameter about structure division. Especially, bending stiffness of elastic body has a lot value depending on young's modulus, cross-sectional shape and thickness. As a result, flow fields around the elastic airfoils with same bending stiffness value are thought that are different. In the present paper, we simulate the flow field around the elastic heaving airfoils by fluid structure interaction simulation using ANSYS 14.0/ANSYS CFX 14.0.

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The purpose of this study is to show the determination of drag coefficient in polygonal plates. The shape of polygonal plates were equilateral triangle, square and equilateral pentagon. The drag of plate was measured by using a load-cell at Reynolds number(Re) about 3.0×10^4 to 6.0×10^4. The drag of polygonal plate was compared with the drag of circular disk, which has same area with polygonal plate. The determination of drag coefficient in polygonal plates was showed by using the number of corners of the plate as a parameter.

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Tokai University and King Abdulaziz University(KAU) in Kingdom of Saudi Arabia has developed a solar powered unmanned aerial vehicle(UAV) under the collaborative project between the universities. In this study, in order to obtain the detail aerodynamic data of main wing, the wind tunnel tests of the three-dimensional wing model, which is based on the same airfoil, SD7037, as the actual main wing of our solar UAV, was performed by using the low speed wind tunnel in Tokai University and its aerodynamic characteristics such as lift coefficient and drag coefficient were obtained. From the results, it was cleared that the roughness is effective to control the boundary layer on the surface of the wing and the aerodynamic characteristics were improved by attaching the roughness using the carborundum, which are two types of size, #100 and #1000.

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In order to understand the aspect of the mutual interference flow from two circular cylinders, the visual observation experiment was performed. The steady case experiment was performed by making three kinds of distance ratios (L/d=1.5, 2.5 and 5.5), and seven kinds of arrangement angles(α=0, 15, 30, 45, 60, 75 and 90 degrees) into experiment parameters. The oscillating case experiment was performed by making two kinds of amplitude ratios(2α/d=0.25 and 0.5), and the oscillation frequency ratio f/f_K in 24 steps. The Reynolds number was about 640. As the result of experiment, even if the distance ratio was the same, the vortex shedding characteristics changed with arrangement angles. The mutual interference will become remarkable if the distance ratio is small. In the arrangement angle, 30 degrees and 45 degrees are carrying out mutual interference most. Even when a forced in-line oscillation was performed under the conditions in which two circular cylinders are carrying out mutual interference, it was found that a lock-in phenomenon occurs. The vortex shedding characteristic was obtained.

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The mixing phenomena of density stratified fluid by jet flow in a tank are experimentally investigated. The jet issues vertically upward from a circular nozzle mounted at the bottom of the tank into the density stratified fluid composed of water and salt water. The jet Reynolds number Re varies from 80 to 4200, and the salt density ranges from 2 to 8 percent. This study classifies the jet behavior into three patterns according to the Re and the density difference between the two fluids. The patterns are discussed in relation with the mixing phenomena caused by the jet.

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Structures of vortex rings in circular synthetic jets are studied by smoke visualization. The smoke particles engulfed by the vortex rings are illuminated by thin sheet of laser light and the motion the mushroom shaped smoke patterns by vortex rings are recorded by a high-speed digital camera. The experiments are carried out for 5 driving conditions of dimensionless stroke L/d range from 0.725 to 4.74 at Reynolds number Re ≈ 2500 and 6660. The visualized images show that the vortex rings rolled up from the orifice form an array of vortex rings and travel to downstream. In some distance from the orifice, the vortex rings are collapsed. During the collapse of the vortex ring, no direct interferences with other vortex rings are observed. The visualized cross sections normal to jet axis indicate that there exist small and irregular pattern inside the vortex rings.

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The decay characteristics of grid turbulence were investigated by means of laboratory experiments conducted in a wind tunnel. A turbulence-generating grid was installed at the entrance of the test section for generating nearly isotropic turbulence. Five grids(square bars of mesh size M= 15, 25 and 50 mm and cylindrical bars of mesh size M= 10 and 25mm) were used. The solidity of all grids is σ=0.36. The instantaneous streamwise and vertical velocities were measured by hot wire anemometry. The mesh Reynolds numbers were adjusted to Re_M = 6,700, 9,600, 16,000 and 33,000. In each case, the result shows that the decay exponent of turbulent intensity is close to the theoretical value of -6/5 for Saffman turbulence. Furthermore, each case shows that streamwise variations in the integral length scales L_<uu> and L_<vv> and the Taylor microscale X grow according to L_<uu>〜2L_<vv>∝(x/M-x_0/M)^<2/5> and λ∝(x/M-x_0/M)<1/2>, respectively, at x/M > 40-60(depending on the experimental conditions, including grid geometry), where x is the streamwise distance from the grid and x_0 is the virtual origin. We demonstrated that in the decay region of grid turbulence, u_<r.m.s>^2L_<uu>^3 and v_<r.m.s>^2L_<vv>^3., which correspond to Saffman's integral, are constant for all grids and examined Re_M values. Consequently, we conclude that grid turbulence is a type of Saffman turbulence for the examined Re_M range of 6,700-33,000 regardless of grid geometry.

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In this study, we aim to construct a finite difference method, which spatially and temporally conserves the kinetic energy, for the vorticity equation on the two-dimensional flow field. In order to achieve the temporal kinetic energy conservation, a space-time staggered grid is used for the discretization of governing equations and implicit mid-point rule is applied to the time integration. The method is applied to simulate a two-dimensional homogenous isotropic turbulence. The simulation results show that the method can conserve the total amount of kinetic energy regardless of the time interval, clarifying the usefulness of the method. In addition, the solution methods for the nonlinear simultaneous equations which are obtained from the discretized equations are investigated. The results show that the SOR method is much faster than the Jacobian-free Newton-Krylov method with the GMRES method for the Krylov iteration.

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Lift and drag of a symmetric airfoil with miniature electromagnetic actuators have been measured in the low Reynolds number region from 30,000 to 100,000. The effect of the operation of the actuators has also been demonstrated under the condition that a wind speed has suddenly been decreased and that should have leaded to the stall if no-actuation. It was found that both of the coefficient of the maximum lift and the stall angle of attack increased as the Reynolds number was increased. The actuation made the coefficient of the maximum lift and the stall angle of attack larger than those in the no-actuation case for each Reynolds number. Even in the case of the wind speed decrease, it was demonstrated that the actuation was effective to avoid the stall and to keep the high lift equivalent to each wind speed. Feedback control using increase/decrease of angle of attack was also effective to maintain the high lift in the case of the wind speed decrease and the additional feedback operation of actuators worked well to suppress the abrupt decrease of the lift.

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This paper describes the experimental study of the dynamic characteristics of a new non-contact type suction device. The present study has been carried out for handling technology in various environments. The main aim was to obtain high suction force in non-contact. We propose a new non-contact type suction device. The jet of nozzle ring flows along surface of device by coanda effect. Eject effect caused by the coanda effect decreases pressure in inside area of nozzle ring. The pressure brings strong suction force. This time, we examined the dynamic behavior by traverse equipment mounted the suction device. As a result, the behavior to upward is depended on vertical vibration. That is suggested that we have to consider dynamic characteristics with vibration.

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This paper describes the experimental study of the characteristics of a non-contact type suction device using Coanda effect. The present study has been carried out for flow analysis around a non-contact suction device. The main aim was to obtain the useful data for CFD analysis by suitable visualization. TiO_2 particle shows the difference of the flow pattern around the non-contact suction device with work and without work well. It is found that the range of the flow velocity is too wide to fix the suitable photography condition. Constant Temperature Anemometer (CTA) is also applied to measure the flow velocity. The strong turbulence of air flow is observed around the non-contact suction device.

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A work dynamics with non-contact suction device is studied by computational simulations. Assuming suction force, drag force and gravity force act on a work, the dynamical model is derived. By calculations of this model, it is shown that a conveyed work generates a vibration. This vibration is occured by the potential energy of suction force and gravity force. The more massive work for same suction force, the amplitude of vibration is higher. The relationship between suction force and inertia is relative, it is expected that the vibration is reduced by controls of suction force of the device.

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Flow separation is mostly an undesirable phenomenon and boundary layer control is an important technique for the separation problems on airfoils. A synthetic jet actuator is considered as a promising candidate for flow control applications because of its compact nature and ability to generate momentum without a need for fluidic plumbing . In the flow fields where the separation control is not needed, parasitic drag can be avoided with the jet flow turned-off. If the control device operates only when it is necessary and can adaptively suppress flow separation, the ideal flow corresponding to the flow under its design condition is always attained without any changes in design of airfoils. In this study, wind tunnel tests for an airfoil installed active boundary layer control system using the synthetic jet were performed. The experimental results indicate that the maximum lift coefficient increases 11%, and the stall angle is to rise by 4 deg in contrast to the case under no control. It was confirmed that our proposed system can suppress stall on the NACA0012 airfoil and the aerodynamic performance of the airfoil can be enhanced.

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This paper described on the controllability of jet shear layer excitation by sound wave to which apply an argon atmospheric-pressure plasma jet. Our previous study showed periodic swing and stretching motions of the plasma jet by the excitation, but the bound condition of the method is still not clear. We, therefore, investigate the limit of the control. A visualization of the plasma jet was conducted by use of a high speed video camera, and we analyzed spatial and temporal motions of the jet via image processing, and then its controllability was estimated. As a result, the asymmetric mode enhances the jet oscillations as increasing with the sound amplitude, but the symmetric mode only affects the jet stretching. The excitation conditions; amplitude and frequency show significant influence on the jet behavior. The detail phenomenon which focused on nature of the working gas and the surround fluid will be presented in the conference.

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A dielectric barrier discharge (DBD) plasma actuator has been investigated as a device for flow control by many laboratories. In this study, we try to use it for jet diffusion. Up to now, to promote the diffusion of the jet flow, we had examined the influence that the generation flow exerted on the jet flow by continuously generating plasma. This time, we examined what influence the generation flow exerted on the jet flow by giving plasma an intermittent control. In the actual experiment, we examined what influence the generation flow exerted by controlling intermittent by using coaxial type DBD plasma actuator set up at the nozzle exit, and changing the value of intermittent ratio duty and intermittent frequency f_d in the early region of the jet flow. As a result, it was able to be confirmed that a center speed decelerated by controlling intermittent in the early region of the jet flow.

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In order to improve the performance of heat transfer with multiple impinging jet(MIJ), we investigate the DNS (direct numerical simulation) of four round impinging jet arranged at an inflow of flow field. As a control parameters, a separation between each jet is varied. From view of instantaneous vortical structures and time-averaged velocity distribution, it reveals that the generation of vortical structures are enhanced due to an interaction between each jet, compared to that of a single impinging jet, and that various type of upward flow which does not exist in the single one, appears according to the control parameter. In addition the heat transfer performance of MI J is numerically turn out.

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The purpose of this work is to control the diffusion and the direction of the jet flow issuing from the pentagonal duct. In this study, the velocity measurements of the jet flow issuing from the pentagonal duct with and without the synthetic jet were carried out using hot wire sensors and the constant temperature anemometer. In order to grasp the flow feature the flow visualization was also performed by the LIF method. And decays of the maximum velocity and the jet half value widths were investigated by analyzing the velocity distributions. As a result, it has been found that the jet width with synthetic jet becomes large, comparing with that of the jet without one. Moreover it has been also clarified that the jet is induced by the synthetic jet.

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An impinging jet on lquid free surface is experimentally studied. It is clarified that the depth of the cavity produced by the jet is proportional to the flow rate. Time oscillation of the cavity depth is estimated to be 10 % of the time average.

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The present study focuses on both the effects of an aspect ratio AR and a tip-speed ratio Ω^* upon the tumbling of a flat plate with a low depth-to-width ratio λ = 0.067 - 0.167. The authors carry out measurements using a torquemeter together with the synchronised measurements of a plate's attack angle a for the analyses with a phase-averaging technique, in addition to measurements using a hot-wire anemometer and flow visualisations. As a result, we confirm that there are two torque modes T-modes I and II, as well as two flow-velocity modes V-modes I and II.

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Experimental study was carried out on the flow created by a sphere moving along the axis of a rotating container filled with a viscous fluid. The measurements of the terminal velocity and angular velocity of a sphere, and the three-component velocity fields around the sphere were performed using a PIV system. Flow in a rotating system is governed by the Reynolds Re=w_<s∞>α/v, Taylor T=2Ωα^2/v and Rossby Ro=w_<s∞>/2Ωα numbers, where Ω is the angular velocity of the basic solid-body rotation, wsco and a are the sphere velocity and radius, respectively, and v is the kinematic viscosity. As predicted by the Taylor-Proudman theorem, the so-called Taylor-Proudman column is evaluated quantitatively. For low N (=1/Ro), the drag coefficient C_D is less than the value for N=0, and for large T and N, C_D becomes larger.

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In this paper, the numerical investigation is employed to compute the heat flu on the surface of the heat exchanger. The Prandtl number sets to be 0.71 and the Reynolds number based on the infl w velocity and height of VG is taken to 250. The effects of fl w and heat transfer by two types of VG (delta shape, rectangular shape) and install conditions of the rectangular shape fi is investigated by numerically. The vortex generator of rectangular shape fi is mounted on the bottom wall of the channel, their angles with respect to main fl w are taken to 30°, 45° and 60° and their punched out angles with respect to bottom wall are set to 45°, 60° and 90°. The effects in the wake of VG are examined in above condition and the Nusselt number, pressure drop, bulk temperature, velocity distribution and vortex strength are compared with the various VG conditions, we survey relationship between the vortex strength and heat transfer enhancement.

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The transport of solid particles by a vortex ring launched into water is experimentally explored. A vortex ring launcher, composed of a cylinder and a piston, is mounted at the bottom of a water tank. Small polyacetal particles are placed on a mesh stretched on the cross-section of the cylinder. The water in the cylinder is discharged vertically upward into the tank by the piston to launch the particle-laden vortex ring. The Stokes number is 0.75, and the number of particles is 99. Immediately after the launch of vortex ring, the particles are entrained into the vortex core, and the particles are transported with the convection of vortex ring. The entrained particles drop out from the vortex core, and fall vertically with the convection of vortex ring. The strength of vortex ring reduces due to the entrained particles, and the convection velocity also lowers. At the displacement of the vortex ring where the marked reduction of the strength occurs, the vortex ring loses its transport ability.

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Turbulent jets are utilized in various industrial devices such as combustors and ejectors. To control jets and enhance mixing, several devices have been developed, and mixing process also has been studied. For the practical applications, such devices should be simple, reasonable and durable. Oscillating jets are effective to enhance mixing. In this study, a flapping jet is focused for mixing passively. The flapping jet is a self-excited flow which emerges from a fluidic device. The fluidic device consists of a slit nozzle with a rectangular chamber. From the flow visualization, it is found that the jet flaps inside a chamber accompanying with reverse flows from the outside of the chamber, and it becomes a periodical large-scale motion outside the chamber, the configuration of the nozzle and the chamber for the stable oscillation is also found. From the measurement of mean velocity profiles, the flapping jet is found to have a large spreading angle and shows remarkable decay rate of mean velocity. In addition, it is noticed that the frequency of the flapping jet varies depending on the chamber size.

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The flow characteristics of a plane jet with serrated tabs were investigated experimentally. Serried isosceles triangle shaped tabs are lined 6mm pitched and have a slant angle of β=45, 90, 135°. The effect of slanted serrated tabs on the mean and fluctuating velocity profiles of jets were measured by hot-wire measurement and flow visualization using oil mist. The mean exit bulk velocity of the plane jet was changed approximately 7.4 m/s and 11.3 m/s. Serrated tabs breaks up the large scale vortical structure and suppress the spread of jet. When tabs are slanted to downstream (β=45°), longitudinal vortices generate around the tabs and interact with the adjacent vortices which leads to the increase of turbulent intensity. For the jet with the mean exit bulk velocity of 7.4m/s, tabs slanted to upstream (β=135°) suppressed the spread ofjet at x/H<8.On the other hand, tabs slanted to downstream (β=45°) suppress the spread of jet at x/H>8.

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Velocity fields of parallel circular jets were investigated experimentally. Air jets were issued from circular orifices arrayed at an equal interval in a line. The interest of the present study is to know an influence of the interval of the parallel jets. Velocity was measured by a single normal hot wire probe, and fundamental properties such as jet width, jet cross-sectional area, flow rate and entrainment ratio of jets were discussed. The experimental results suggest that the streamwise variations of mean velocity and turbulence intensity, and the jet cross sectinal areas are almost same among the parallel circular jets with different intervals. And flow rate seems to increase in proportion to number of jets, and the jet entrainment is increased with increasing the interval of the jets.

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The laminar-turbulent transition of a mixing layer excited by oscillating flat plates at an exit of a two-dimensional nozzle was experimentally investigated. The mixing layer was formed between the jet issued from the nozzle and the surrounding quiescent fluid. The plates oscillated vertically in relation to the mean flow. Upper and lower flat plates oscillated anti-symmetrically. The oscillation frequency, 5 Hz, was two orders of magnitude smaller than the fundamental frequency of the velocity fluctuation. Mean and fluctuating velocity components in the streamwise and normal directions were measured by hot-wire anemometers. The results were compared with the previous case in which the plates oscillated symmetrically. Anti-symmetrical oscillation promoted the expansion of the mixing layer and promoted the disappearance of the potential core more than symmetrical oscillation. The fluctuations from time and phase averages in the anti-symmetrical oscillation were larger than those in the symmetrical oscillation. The contribution of periodic fluctuation disappeared downstream in the symmetrical oscillation but persisted longer in the anti-symmetrical oscillation.

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Experiments were performed to investigate the effect of a line of roughness elements on a flat-plate boundary layer transition. Each of 11 roughness elements was a cylinder 2 mm in both diameter d and height k, forming a row with an interval of a 22 mm in the line of elements in the spanwise direction. Wedge-shaped turbulent regions ("turbulence wedges") developed downstream from the respective roughness elements. Farther downstream, two adjacent wedges merged and a two-dimensional turbulent boundary layer was then formed. Turbulent energy production rates, Reynolds shear stress, turbulent energy dissipation rates and fluctuating velocities were measured by hot wire anemometers inside and outside the wedge regions. The relationship between the turbulent energy production rates and the turbulent energy dissipation rates was examined.

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The effect of localized external disturbances on the receptivity of a fla plate boundary layer is investigated by a wind tunnel experiment. The disturbances are introduced in the free stream using the combination of the optimally designed airfoil and the jet ejections from the trailing edge. The experimental results show that the velocity fluctuatio in the boundary layer grows up rapidly when the disturbances comes close to the outer edge of the boundary layer. When the jet is pulsated at 10 Hz and 30 Hz, the velocity fluctuation of the same frequency is observed in the boundary layer.

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In this paper, we investigate the mechanism of velocity pulsation on circular wind tunnels with open-type test section and propose a pulsation suppression method. The test section of wind tunnel was lengthened for generating the strong pulsation in the air flow. The pulsating flow was visualized with a smoke-wire technique and the velocity was measured by hot-wire anemometer. The experimental result explains that the vortices in the mixing layer have an influence on the pulsation, because the frequency of vortices striking the collector is the same as that of pulsation. For the reduction of the pulsation, we placed a resistance object near the collector. As a result, the turbulent intensity was suppressed by 59%, and the distinguished frequency, the characteristic of the pulsation, disappeared.

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Elucidation of turbulent diffusion phenomena are of practical importance with many engineering and environmental fields (e.g.,in the combustor design and the prediction of pollutant diffusion). In order to clarify turbulent diffusion field experimentally, it is useful to measure instantaneous concentrations of multiple species simultaneously in a turbulent flow. In the present study, measurement system for concentrations of three species using absorption method has been developed, and instantaneous concentrations of three species in a turbulent jet were measured. Three laser diodes (LDs) with different wavelength are used as light sources; red LD (635 nm), green LD (532 nm), and blue LD (488 nm). It is confirmed that the instantaneous concentrations of three species in the turbulent jet can be measured by the present measurement system.

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Conditional statistics, conditioned on mixture fraction, are experimentally investigated in a planar liquid jet with a second-order reaction (A + B →R). The reactant A is premixed into the jet flow, and the reactant B is premixed into the ambient flow. Concentrations of reactive species and mixture fraction are simultaneously measured by using an optical fiber probe based on the light absorption spectrometry. The results show that the conditional mean concentration of product R on the jet centerline increases in the downstream direction because of the progress of chemical reaction. It is also found that the conditional mean concentration of product R does not depend on the lateral position of jet flow in the downstream region and the outer region of jet in the upstream region.

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A fuel injector with multi-swirl nozzles for producing fine atomization of a fuel spray was developed. The multi-swirl nozzles were composed of swirl chambers placed in the upstream of orifices. A swirl flow produced by the swirl chambers forms thin liquid films on orifice walls by centrifugal force, and these films break up into small droplets outside the orifices. We related thin-liquid-film properties to the droplet size of the fuel spray. The fuel flow within the swirl nozzle was simulated by using the Volume of Fluid (VOF) method, and the simulated velocities and the width of thin liquid film were used to predict the droplet size and spray angle of the fuel spray. Miyamoto's atomization model was applied to connect a circumferential velocity and the width of the liquid film at the orifice outlet with the droplet size. It was found that the droplet size and spray angle of multi-swirl nozzles were predictable by using the VOF method and Miyamoto's atomization model.

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A shear coaxial injector is widely adopted for liquid rocket engine because its structure is exceedingly simple and it has excellent combustion efficient. In general shear coaxial injectors for liquid rocket engine which uses LOX/LH2 as propellant, LOX is injected slowly from central tube (LOX post) of injecter and fast GH2 jet is injected annularly from around the LOX post. Even though shear coaxial injector has excellent characteristics of combustion stability, however, it is considered that combustion instability can be induced under specific condition. For this reason, we investigated behavior of LOX jet under hot fire condition by using high-speed shadowgraph imaging. As a result of this investigation, it was found that there is a relationship between instability of LOX jet and pressure situation in recessed region. Furthermore, it was confirmed that length of LOX core shorten by increasing ratio of injection velocity of each propellant.

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The three-dimensional time dependent compressible Navier-Stokes equations are numerically solved to study acoustic emission nature in a supersonic round jet at high convective Mach number (M=2.0) using high-order compact upwind schemes. Two cases for Jet Mach number M=2.0 are presented. The first case is the jet flow forced randomly. The second case is the jet forced by random disturbances and first helical modes with the counter rotating direction relative to the dominant helical modes in the acoustic field for the random disturbance case. The numerical results show that the jet forced by random disturbances and first helical modes can restrict the emission angle of Mach waves due to the modes interference in the jet potential core region.

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Steady, periodic and traveling-wave solutions of the flow through a curved square duct are obtained numerically, and their linear stability to two- and three-dimensional disturbances is investigated. It is found that a steady traveling-wave (STW) solution bifurcates from the symmetric steady solution branch and is linearly stable in the intermediate range between low and high pressure gradient regions. Two stable periodic traveling-wave (PTW) solutions are also found, which have oscillating components with different symmetry. One keeps the same symmetry as the STW solution and the other breaks it. It is strongly suggested that a two-dimensional time-periodic (2DP) solution is created via heteroclinic bifurcation, not from local bifurcation. 2DP solution is always linearly unstable against three-dimensional disturbances though it has linearly stable region to two-dimensional disturbances.

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An accelerated flow through a curved pipe has been studied experimentally. It is very useful to investigate such an unsteady flow experimentally for improvements of mechanical efficiency or early detections of disease. In the present experiment, for an abruptly-accelerated flow from rest to Reynolds number Re=2x10^4 in a curved pipe, we measured distributions of axial velocity, wall static pressure and wall shear stress using a hot-wire anemometer and a static pressure gauge simultaneously

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The micromixer, which has a rotor with a curved channel, is studied experimentally. The Taylor-Dean flow in a curved channel of rectangular cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods. Two walls of the channel (the inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. The non-dimensional channel curvature δ=α/R is taken to be about 0.1, where 2α is the width of the channel, R the curvature radius of the channel. Other non-dimensional parameters concerned are the Dean number De=Reδ^<1/2>, where Re=qd_h/v is the Reynolds number, q the mean flow velocity in the channel axis direction, d_h the hydraulic diameter of the channel, v the kinematic viscosity, and the Taylor number Tr=2α^2Ω(2δ)^<1/2>/(δv), where Ω is the angular velocity of the rotor. Photographs of the flow in a cross-section at 180° downstream from the curved channel entrance are taken by changing the flux (De) at a constant rotational speed (Tr) of the channel walls. It is found that good mixing performance is obtained in the case of De %le; 0.1|Tr|. This tendency appears more strongly if aspect ratio is large. And then we have confirmed the occurrence of reversal of the mean axial flow.

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An experimental study is performed for dividing turbulent channel flow in 90 degree T-junction with sharp and various shape corners. Experiments are conducted for flow rate ratios of 0.2, 0.4, 0.6 and 0.8 (ratio between the flow rates in the branch and main channels) keeping the Reynolds number of the main flow at 4.0x10^4. The width of main channel H_1 is kept to 30mm, and the width of the branch channel H_2 is changed 15mm, 30mm and 45mm. The wall static pressure is measured and loss coefficient is evaluated. The velocity profiles are measured by a PIV system. The results show that rounding the corner reduces the pressure loss in the branch flow. As the ratio of width of the main channel to branch channel decreases, the reduction of pressure loss in the branch flow becomes large. It relates that the reattachment length is shorter compared with that of the sharp corner. Whereas the pressure loss in the main flow basically remains unaffected.

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The cleaning process of a silicon wafer is important in the manufacturing of semiconductors, which determines the quality of the final products crucially. In the so-called single wafer cleaning, a wafer washed with cleaning solution and rinse liquid is dried up by rotating at a high speed. We made an experimental apparatus which has a similar structure to the single wafer cleaning chamber, and measured the velocity field in the chamber by the particle image velocimetry(PI V) method.

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The power consumption of an air conditioner in an electric vehicle has a considerable impact on the cruising range. A high-performance magnetic refrigerator is therefore one of the important technologies needed for future electric vehicles. The requisite conditions for an in-vehicle magnetic refrigerator are higher with respect to cooling power density, temperature difference between the hot and cold sides, transient properties, and coefficient of performance than those of household refrigerators or home air-conditioners. We have devised a new model without a refrigerant in which heat is transported from the cold to the hot side through well-controlled thermal switches. A test rig to verify a heat transfer mechanism of the model and its numerical model have been created. The thermal resistance characteristics of the test rig have been experimentally derived. The characteristics have been input into the numerical model. The heat transfer mechanism and heat transport characteristics have been verified both experimentally and numerically.

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In relation to the efficiency of heat pump system, basic experimental researches have been carried out on frosting and defrosting phenomena under forced convection at various level of humidity. Effects of surface properties on frosting and defrosting phenomena were investigated. Copper fin is coated by hydrophobic paint. In frosting process, surface temperature of coated fin showed higher temperature, compared with uncoated fin due to the thermal resistance of the coated material. Using hydrophobic paint mixed with material having high thermal conductivity, temperature rise of coated fin is considerably suppressed. At early stage of frosting process, configuration of frozen droplets at cooled fin is considerably different between coated fin and uncoated fin. Time needed for defrosting process is shortened about 30seconds for coated fin compared with uncoated fin.

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A power system demand analysis toward a year of 2030 has been performed on the basis of Japanese government strategy formulated in 2012. We have quantified the effect of an introduction of a large amount of renewable energy over power supply operation by incorporating an evaluation of frequency control capacity into our optimization results. We reveal the critical shortage of the frequency control capacity available in whole power system, which is caused by the penetration of renewable energy. We also discuss the measures to resolve this issue from the practical viewpoint of power supply operation.

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A technology of carbon dioxide capture and storage (CCS) is the one of global warming countermeasure. As an oxidizer in advanced integrated coal gasification combined cycle (A-IGCC), the utilization of mixture gas including carbon dioxide (CO_2) and oxygen (O_2) is discussed. In the present study, a coal gasifier with two-stage entrained bed was numerically simulated to investigate the adaption of O_2/CO_2-blown system in gasifier. Thermal loss on the gasifier furnace wall was considered in this simulation. Because the reaction of coal gasification was promoted by CO_2, we can operate the gasifier system for low oxygen ratio compared with the conventional system. By the control of the reactor/total coal ratio, we can easily operate the gasifier system. At the O_2/CO_2-blown system, high level gas heating value was obtained and the operation range with safety combustion became wide. We can expect the enhancement of thermal efficiency of power generation and the reduction of reductor length for the operation of low oxygen ratio.

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