Ablators with lightweight and high performance thermal insulation property are required in order to suppress the weight of thermal protection systems for re-entiy capsules of next-generation spacecrafts. Conventional ablators have been mainly made of phenolic resin matrix CFRP. In this study, we are aiming at development of new ablators with lightweight and high thermal insulation performance, and for this purpose, we employed porous carbon materials, which have a three-dimensional network structure. Porous carbon materials were made by carbonizing porous resin which can control the diameter of the pores. Experimental results showed that thermal conductivity of this material got smaller when the pore diameter decreased and it was relatively low value compared with other porous carbons. Ablators were manufactured by impregnating polyimide resin into the porous carbon material, and by curing them. However, the curing proceeded non-uniformly. In order to obtain uniformly cured ablators, an optimal diying process was studied. Then, thermal conductivities of the manufactured ablators made of the porous carbon material with various pore diameters were evaluated. The thermal conductivity depended on the pore diameter similar to the material before curing, and was less than 0.3 W/(mK). These results suggested that this material is promising candidate for a new lightweight ablator.

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This paper deals with a model to estimate an internal stress during sintering of ceramics laminates. This model was discussed previously, however, the authors have modified it into a more general form recently(especially cooling process during sintering). In this model, a symmetrical 3-layered laminate is considered, and one-dimensional elastic analysis is carried out. For heating, soaking at the sintering temperature, and cooling processes, the elastic stress in each constituent is given by using its sintering strain, thermal expansion strain, Young's modulus and volume fraction. Compared with the strength of each constituent sintered at the intermediate temperature, crack formation during sintering can be discussed.

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The 3.11 East Japan huge earthquake brought people the importance and countermeasure against a sudden natural accident not only in Japanese that lives in the technical advanced country but the collapse of the artificial technical safety myth around the world, and it will serve as a historical big warning to the future social technology development. For that purpose, the revolution of the design viewpoint of the mechanical system technology in our society becomes indispensable, that is to say, the machines which should correspond to flexible, adaptive and with more smart functions, i.e., a disaster prevention sensor, high performance, efficient energy conversion actuator device, the automation controlling method, the man machine interface robot, society's infrastructure management engineering system etc. with IT wireless communications network etc.. Based on the above situation, the possibility of the engineering innovation creation, social and economic effect by the fusion technologies based on smart material and system component will be outlined by combining the research-and-development of disaster reduction and sustainable technology.

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Combining the new Fe-based magnetostrictive alloy for high-output oscillating power generation (Hirosaki University), the piezo-electric fiber containing a metal core(Chiba University and AIST) having stress-direction detection sensor and wireless module are installed inside of the rotation tire, a prototype wireless tire-sensor for wheel vibration and the distortion action from a road surface with vibration energy harvesting devices was developed as an preliminary experiment. From the information on modification and the vibration state of the grounding wheel side can be collected and analyzed in real time, the time-dependent changes of tire-condition and the dangers on the street such as a freeze, snowfall and road surface quality will be detected. It can be contributed to driving safety as well as an intelligent transport system for near future automobile society.

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In this work, TiO_2/Ti composite films were fabricated by 2-setp MCT and the following high temperature oxidation. The microstructures of the surface and cross-section were observed by SEM. Photocatalytic/antibacterial activity of the composite films treated by ultrasonic cleaning to increase the performance reliability was examined. The results revealed that 2-setp MCT is a simple and useful process to prepare TiO_2/Ti composite films on alumina balls. Relative high photocatalytic activity was still kept after ultrasonic cleaning. The prepared TiO_2/Ti composite films showed high photocatalytic activity in the degradation of methylene blue solution. It is obvious that TiO_2/Ti composite films have antibacterial activity under UV irradiation.

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Chemical interface controlled dispersion and high speed shearing(CDS) washing verification test of high level radioactive contaminated soil over 570,000Bq/kg was conducted using three kinds of radioactive contaminated soils of school ground, moor and road in FUKUSHIMA and the following results was obtained. (1) Washing rate of three kinds of contaminated soils reached up to 60-98% after 60minitues CDS water washing. (2)Recovered amounts of reclamation soils of three type of soils(<8,000Bq/kg) were 60-82wt.%, Especially, 506Bq/kg×33wt.% was achieved in the case of contaminated soil of moor. (3) Volume reductions of 60-85wt/% were achieved in every case of contaminated soils. (4)Contain recoverable quantities of total radioactive sources contained in soils was over 90%. (5) Main FP trapping minerals contained in contaminated soil of school ground is lamellar silicate and that of moor and road is mordenite.

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It is proposed that the technique to generate planar elongational flow with high elongational rate by using core/sheath flow. In this study we carried out experiments to observe flow behavior for both viscous fluid and viscoelastic fluid in the flow. In case of viscous, we compared experimental results of velocity distribution along a centerline of the flow cell to analysis results under the two-dimensional Poiseuille flow and they show good agreement. On the other hand, it is observed for viscoelastic fluid that flow behavior of the core fluid shows four kind of flow patterns from result of flow visualization and velocity profile, that is, swelling, stretching, stretching before conjunction region and instable flow. Next, we evaluated molecular orientation profile of elongated fluid by using crossed nicols method. As the results, measure of molecular orientation doesn't depend on the distance to sidewalls of the flow cell in elongational flow region. It is shown that contribution elongational property to the flow can be discuss from results of distribution of molecular orientation along center line of the flow cell.

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In the present study, we report and discuss that an apparent slip on a wall of a microchannel has been observed with polymer solution flow. The aqueous solutions of polymer, which are non-Newtonian fluids, used in our experiments are anionic and nonionic ones, respectively. An aqueous solution of glycerin, which is Newtonian fluid, is also used for comparison. The wall of microchannel is made of two types of glass: normal glass and ITO(indium tin oxide)-coated glass. The ITO-coated glass is also transparent. The flow channel is constructed by having a glass plate and PDMS chip (silicone rubber) bonded. In the experiment of anionic polymer solution, the apparent slip was observed on the wall of normal glass, but not with the one of ITO-coated glass. For the nonionic polymer solution, the apparent slip was observed both on the normal and ITO-coated glasses. These phenomena are caused by the interaction between the polymer and the wall.

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Flow structures of a polymer solution in a planer channel with a 4:1 abrupt contraction have investigated utilizing an optical rheometric device which is combined with a microscope. Distributions of flow-induced birefringence and velocity field were measured with Xanthan gum solution. The measurement of the birefringence was conducted in every 100μm step along the width direction of the channel. The birefringence measured around the centerline of channel became larger in the converging flow generated in the upstream region of the abrupt contraction. Moreover, in this region, average orientation of the polymer molecules were agree with the flow direction defined with velocity vectors. It is considered that contribution of the elongational flow and the shear flow generated in this region of the planer channel to stretch the polymer molecules has same direction.

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The flow properties and structure of polymer solutions through a slot channel with abrupt contraction were experimentally investigated. We have measured pressure drops and visualized the flows with vortices before the slot. 200ppm and 300ppm aqueous solutions of polyethylene oxide(PEO) were tested and the results were compared with those of water. The normalized pressure drop was plotted against Reynolds number and it was shown that the data curve of the pressure drop deviated from that of water when vortices were generated. After gradual increase in the pressure drop, the curve became parallel to that of water. The increasing ratio after the deviation of PEO 300ppm solution was larger than that of PEO 200ppm. Vortices occurring at low Reynolds number were relatively stable and only show small fluctuations in the span direction. As Reynolds number increased, the vortices became very unstable and moved spirally to span direction.

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The characteristics of oxygen-dissolution accelerated by use of micro-bubbles in a viscoelastic fluid have been studied. An aqueous solution of a combination of a cationic surfactant and of a counter-ion supplier was used as a viscoelastic fluid. Flow visualizations and the time-variation of oxygen concentration measurements were performed. From the results, it was found that the dissolution of oxygen rapidly occurs by use of micro-bubbles, but that the dissolution becomes slow in a high elastic fluid. The flow observation of bubbles in a high elastic fluid showed a chaining effect with the bubble ascension. The bubble chaining accelerates agglomeration of bubbles and decreases apparent gas-liquid interface area. Thus, such a chaining effect was concluded to disturb the dissolution of oxygen.

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The shape of a rising bubble in static non-Newtonian media was presented and discussed in many articles.As for the relation between moving direction and symmetrical axis of the bubbles,most of experimental results show the same direction with the exception that the axis of bubble wobbles slightly in a certain condition.In the case under pressure-oscillating field in 0.8wt% SPA liquid at 300Hz,the cusped shape appears cyclically,in which the 1μL bubble is compressed and rising much faster than its natural rising velocity.However,the moving direction and symmetrical axis are the same.In this study,we observed motion of a 1.8μL bubble in 6wt% CMC liquid under pressure-oscillating field by use of a couple of synchronized high-speed cameras attached to microscopes,respectively.We found that as increasing in pressure-oscillation,the shape of rising bubble changes from spherical to vertically aligned oblate ellipsoid,in which the symmetrical axis is stably horizontal and the axis rotates slowly.

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We have investigated responses of concentrated suspension of non-Brownian spheres dispersed in viscoelastic carrier liquids under stress-sweep test after flow reversal. The concentrated suspensions have showed transient responses after the flow reversal in the shearing direction regardless of the kind of dispersed particle and carrier liquids. In order to evaluate this transient response quantitatively, two typical strains in the transient response were defined. Mono-dispersed suspensions in the particle size were tested with different volume fraction. Influences of the particle volume fraction and particle size on the strains were clarified. Each typical strains was reduced with the volume fraction was increased. The effect of the volume fraction was observed regardless of the kind of carrier liquids. Although there was no size effect in the case of the suspension with Newtonian carrier liquid, the strains were affected with the particle size in the case of viscoelastic suspensions.

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Penetrating flows of an aqueous solution of NaSal into an aqueous solution of CTAB in a circular tube were experimentally studied. When an excess of counter ion is added to a CTAB solution, network structures of wormlike micelles are formed. Thus gelation due to the network formation occurs at the interface between these solutions, and a core part of a penetrating fluid advances with gelling. The behavior of the core part was classified into 5 patterns based on flow visualization experiments, and its dependence on both the molar concentration ratio S of NaSal to CTAB and the penetration velocity was investigated. Furthermore a characteristic behavior such that a necked part of the core region shows elastic recoil was observed at high velocities for S=3.0 and 5.0. The tip of penetrating fluid tends to be more stable for higher molar concentration ratio and for lower penetration velocity.

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We examined the opaque phenomenon of surfactant solutions in an oscillating shear flow. Experiments of flow visualization were performed in a rectangular cavity channel constructed with glass plate. We used the mixtures of CTAB and NaSal as test fluids. From experimental results, it was found that emergence of opaqueness in shear flows was restricted within the neighborhood of a moving glass. Furthermore, in the opaque region, the streak lines synchronizing with an oscillating flow were observed.

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A surfactant, cetyltrimethylammonium bromide (CTAB) forms wormlike micelles in aqueous solutions with additive of sodium salicylate (NaSal). Wormlike micelles can self-organize under flow to form higher-order flow-induced structures (FISs). In this study, flow patterns and a FIS formation are investigated experimentally in the microchannel flow past obstructions. Test fluids used were entangled worm-like micelle solutions of CTAB and NaSal. Steady laminar flow patterns were observed in a water flow, where the flow can be considered as the Hele-Shaw flow. The Hele-Shaw flow pattern was altered drastically in a worm-like micelle solution (3mM, molar ratio 1:1), where the flow was no longer steady. The flow pattern change was accompanied by a formation of FIS in the worm-like micelle solution, which we observed directly with a phase-contrast microscopy. We observed sticky, viscous, transparent streaks of FIS in the fluid flowing down from the obstructions, where the apparent property of the fluid was locally changed. The streaks are having a refractive index different from that of surrounding fluid, but they were hardly observed with bright field images. The streaks were mostly observed in the stagnation flow behind each obstructions as well as the entry flow into the gap between obstructions. The flow with the streaks was heterogeneous and highly unsteady. The fluctuations of the streaks were observed downstream of the obstructions, where the difference in flow velocity across the streak plays a crucial role in the deformation of the streak.

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Basic flow behavior of supercritical CO_2 in solar water heater using supercritical CO_2 is studied for a flow of supercritical CO_2, a small change in temperature or pressure can result in a large change in density and specific heat capacity, especially in the state close to the critical point. Natural convective flow of the supercritical CO_2 can be easily induced by solar heating in the system, when flow characteristics and heat transfer of supercritical CO_2 natural convection are important. An experimental study was carried out to investigate basic flow behavior and thermal transport characteristics of density-driven supercritical CO_2 in a solar water heater using supercritical CO_2.

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A multiphase flow, for example gas and liquid flow, in the mm-μm scale is often used in industrial equipment, and development of prediction technology is important to determine the complicated behavior of a free surface transform. OpenFOAM, one of the open source computational fluid dynamics(CFD) softwares, has recently attracted attention to using in industrial applications. We examined the possibility of using OpenFOAM in the development process of fluid machinery products. First, we started out by a continuous-inkjet simulation. We compared the simulation results for the breakup length of a liquid column with theoretical results. Next, we evaluated a distribution ratio of a refrigerant distributor by another simulation. The simulation results for each model qualitatively agreed well with the theoretical or experimental results. We found that OpenFOAM was effective for the simulation of gas and liquid free surface flows.

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Flow properties of several types of surfactant solutions passing through various sizes of small apertures were investigated in this study. Different fl w properties were found for the various surfactant solutions depending on the charge of the solute. For an anionic surfactant solutions, the resultant pressure drops were similar to those for water, whereas in the case of a cationic surfactant solutions, pressure drops decreased greatly in comparison with the other surfactant solutions. A non-ionic surfactant exhibited a steep rise in the pressure drop at a particular value of the Reynolds number. In explaining this behavior, the liquid-solid interface and alignment of the surfactant micelles are considered, and consequently, it is strongly suggested that the elastic stress is a contributing factor.

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Precession is the motion that the spin axis of a rotating object rotates about another axis. A precessing sphere generates and sustains turbulence of a confined fluid. Using particle image velocimetry, we investigate turbulent velocity fields on the equatorial plane of the precessing sphere. With the additions of cationic surfactant(CTAC) and counterion, sodium salicylate(NaSal), turbulence suppression is observed in a central region of the sphere. When themolar concentration of CTAC(C_D) is kept constant and that of NaSal(C_S) increases, in the range of C_S/C_D &gsim; 1, turbulence is suppressed, while such a suppression is not observed for C_S/C_D = 0.5. For C_S/C_D &gsim; 1, there are fully entangled threadlike micelles in the solution. Moreover, free salicylate ions exist and they promote reconnections of threadlike micelles. This may be the reason why turbulence suppression in a precessing sphere is sustained for a long time in the cases with rich free salicylate ions.

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For cooling systems, adding surfactants to the flow is an effective way to reduce the energy consumption. We investigated the effect of brine(ethylene glycol) on drag reduction in nonionic surfactant(oleyldimethylamineoxide) solutions by measuring the pressure drop in the circuit pipe flow. As the concentration of brine increases, the maximum drag reduction ratio decreases. It is found, however, that the surfactant solution with brine can keep the high level of drag reduction even at the high Reynolds number.

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Nata de coco suspensions reduced the pressure loss in circular pipe flow, and the effect of the drag reduction strongly depends on mixing time of blender for preparing nata de coco suspension. In this study, with respect to the mechanism of the drag reduction, the relation between viscosity, drag reduction phenomena and fiber form of nata de coco was investigated. We found that the nata de coco suspension has a shear-thinning viscosity. The viscosity fluctuation and the drag reduction were observed for the short mixing time (1.5 and 3 min) of blender. A large network of nata de coco fibers formed in this case. In contrast, the viscosity fluctuation and the drag reduction were not observed in the case of long mixing time (10 min) of blender.

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Drag reduction of bio fiber suspensions of silken threads, cotton yarn and hemp fiber in a circular pipe has been investigated experimentally. It was clarified that the wall shear stress of pipe decreases about 15% compare to that of water and it is a proportional to the power of 1.75 of the mean velocity. The pressure drop measurements indicate that the drag reduction depends on Young's modulus, and also the friction factor of bio threads suspensions for Re is classified into the type-B in the drag redaction phenomena as similar to that of bio polymer.

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Aspiration, which is often caused by an incompetent swallowing mechanism, is a serious disorder. One of the solutions for aspiration is using thickener or grated yam in liquid food. The aim of this study is to find the rheology of them and a relationship with swallowing. In this study, we made a extensional flow simulation of grated yam to find out a suitable rheological model, and we also took X-ray videofluorgroaphy (VF) using ten of liquids with different viscosities. We found out that the grated yam has a high extension viscosity and discussed the reason for safe swallowing. We also discussed the shear rate range of liquid food at oral and pharynx which can be used when making a thicken food.

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The purpose of this study is to clarify characteristics of the micro processing utilizing magnetic compound fluid (MCF) inner wall of a horizontal pipe and to investigate flow characteristics of the circumference of a tool. A ring-shaped permanent magnet between spacers stacked in the processing tool with MCF is inserted and rotated in the pipe. In the experiment, the changes of their internal diameter, their material removal and their surface roughness were investigated using the tool with different structure. In order to clarify the processing mechanism, we performed visualization experiment of magnetic clusters without the feed motion of the tool. And the velocity distribution was measured. In addition, the pressure distribution on inner wall of the pipe was measured.

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Numerical simulations of liquid crystalline flows in a rectangular tube have been performed using the Leslie-Ericksen theory. The unsteady profiles of the velocity and director fields at a cross-section of the tube are obtained for both aligning and tumbling nematics. For the aligning nematic, the change in the director field is small and the averaged angle between the director and the flow direction is found to be 11.74deg at the steady state. For tumbling nematic at low pressure gradient, the tendency of the director and the velocity field is quite similar to those for the aligning nematics. On the other hand, for the case of high pressure gradient, the angle between the director and the flow direction becomes larger with time, and finally shows the spatially complex profile, causing the complex profile in the velocity field.

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The flow near the free surface of the meniscus region behind an applicator in application process of a chromonic liquid crystal was investigated. In the case of the applicators that have a knife-edge shaped back wall, the velocity distribution on the surface of the meniscus region is not affected by the gap of the application area. In the case of the traditional shaped applicator, which has a back wall with about 50 degrees angle, the height of the wet line on the back wall of the applicator climbs up during application process and is closely related with the thickness of the dry thin film. The part near the back wall in the meniscus flows reversely and a stagnation line is formed on the surface of the meniscus.

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A parallel disk viscometer was used to investigate the solidification of a photopolymer under shear. Micro-encapsulated thermo-chromic liquid crystal was used to detect the solidification through temperature increase. Under the shear flow, delay of solidification was observed at the radial outer region of the disk, where the shear rate was higher than the inner ragion. In progress of the solidification, the delay was recovered. This delay was induced by the radial non-uniformity of the velocity gradient between the parallel disks.

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At the fields of robotics, sensing for artificial arm and leg, and investigating surface property, the sensor that is applicable to response for shear force as well as normal force has been developed. For the development of the haptic sensor by combining metal particles, we used silicon oil and balloon crude rubbers as naming MCF rubber. The MCF rubbers also involve MCF as one of intelligent fluid constituted by magnetic fluid. The sensor used by the latter rubber has higher quality of sensing for 0.01 N ordered force and of responding at the case of scrubbing any bodies than the one by the former rubber. The difference of the electric characteristics between them is caused by the difference of the electric mechanism depending on oleophilicity and hydrophilicity.

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We numerically examined the induction of spoke pattern on Rayleigh-Benard convection(diameter/vessel height=10, Pr=6.0, Ra=1.0x10^4) varying the vertical and redial components of magnetic force. We investigated the influenceof the magnetic force by using 2 turns coil as well as the actual conventional magnet of 1800 turns coil. As the results, the radial component was found to be so important to induce the spoke pattern on convection.

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We applied a fuel-spray simulation to sprays from fuel injectors with multi-hole nozzles for direct injection gasoline-engines. Both fuel flows within the flow paths of an injector and liquid column at the injector outlet were simulated by using a grid method. The liquid-column breakup was simulated by using a particle method. The motion of droplets within the air/fuel mixture region was calculated by using a discrete droplet model. To verify the simulation model, simulation results were compared with measurements. Simulated spray penetrations agreed relatively well with measured spray penetrations. Effects of velocity distribution on spray penetration were studied. We found that high-speed region within nozzles increased the spray penetration.

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Detonation is a combustion wave that propagates at the supersonic speed in a stationary reactive mixture in the form that consists of a precursor shock wave and a reaction region induced by the shock. In addition, the detonation front is known to have shock triple points which are composed of an incident shock, reflected shock and Mach stem shock. In this study, a one-dimensional detonation was analyzed at first. Second, the three-dimensional detonation at a rectangular tube was analyzed in the moving coordinate system, using the one-dimensional result as an initial condition. And last, the three-dimensional detonation propagating in the tube with a right corner was analyzed in the stationary coordinate system, using above-mentioned three-dimensional results as the part of initial condition. The results of this study are as follows: Results due to a change of coordinate system are no large difference, but the detonations in over-driven condition propagate a short while at the start of calculation. When the detonations propagate into a large space, its configurations collapse by the Prandtl-Meyer expansion and the long induction length. When the detonation propagates into a narrow space, part of the triple points disappear once, but its configuration re-generates by interference with the reflected wave and collisions with the wall. No large differences are shown on results of the propagation behavior due to location of the triple points just before diffraction.

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This study is a numerical analysis on propagation behavior of a three dimensional detonation in a square tube and, influence on motion trajectories of high pressure region(shock triple points) due to the change of aspect ratio of tube was solved by a finite difference method which consists of the semi-implicit MacCormack method and TVD scheme in order to prevent numerical stiffness and Gibb's phenomena. Gas utilized in this computational study is the stoichiometric hydrogen and oxygen gas mixture. It was found from numerical results that Change in propagation mode can be explained from the relation between the geometric form of a section and the behavior of triple points. Moreover, it was shown that the instability of the propagation form and propagation mode may not be settled causing the aspect ratio of the section.

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PSJA(Plasma Synthetic Jet Actuator) is an electric device for flow control utilizing barrier discharge phenomenon. To avoid electromagnetic interference with other devices, it is important to analyze electromagnetic waves emitted by PSJA. This paper carries out a simulation of electromagnetic field distribution by FDTD method using barrier discharge model, where the electromagnetic field is assumed to be generated by discharge current between the electrodes. The result shows that the electric field is directed from exposed electrode toward insulated electrode, and the magnetic field component parallel to discharge current is very small relative to the other components.

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Gas-liquid plasmas for medical treatments have been developed and it includes many physical phenomena such as discharge, flow dynamics, chemical transport and heat transfer. Thermal flow field induced by a gas-liquid plasma is one of the important phenomenon though the mechanism of the flow drive was not clarified yet. In this study, we focused revealing the effect of directions of electric fields on the direction of the induced flow experimentally. It was found that the direction of the electric field govern the formation of the gas flow.

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The induced jet characteristics of trielectrode(TED) plasma actuators on quiescent air were analyzed. To mitigate the non-uniform discharge nature for sliding discharge on the TED plasma actuator, the notched, saw-tooth electrode was employed for their DC electrode. The observation of the discharge and visualization of the jet revealed that the discharge start from the apices homogenized the density of sliding discharge, resulting the mitigation of two dimensionality of the induced jet of the TED plasma actuator.

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In this paper, an experimental evaluation of a burst wave induced plasma actuator(BWPA) as a flow control device adding a periodic disturbance was performed. The periodic operation mode of a dielectric barrier discharge plasma actuator(DBD-PA) is expected to be a promising way to control the separated flow in low Reynolds Number, in which the share layer has an acceptance frequency for excitation. A transient behavior of velocity induced by BWPA was measured in quiescent air using particle image velocimetry(PIV). The results indicates that the velocity response has approximately an exponential behavior and the time constant of the response is independent of the burst frequency and duty ratio. As an application of BWPA for separation control, a reduction rate of reattachment over a backward facing step flow in low Reynolds Number was examined. It is classified that BWPA is more effective than continuous-wave based PA in the separation control. The velocity amplitude in the modulation is considered to be one of the most important parameters to control the flow. As a result, approximately 40% of the reattachment length reduction was achieved in Re = 500 under the velocity amplitude = 0.4[m/s].

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We change applied voltage waveform of a plasma actuator in numerical simulation, and analyze how ion transport and body force change. When applied voltage waveform of a PA is changed, body force of a PA is changed. Especially voltage waveform between the positive peak value and the value that voltage is zero from positive effects to keep body force of a PA and to make back flow.

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In this study, we numerically investigate the flow induction process of DBD plasma actuator, which consists of the plasma evolution, the body force generation by the particle collisions and the flow induction by the body force field. In order to understand comprehensively these processes, coupling simulation of discharge plasma and induced flow is necessary. As the start of this study, incompressible Navier-Stoke simulation and discharge plasma simulation are alternately conducted; flow field is simulated using the body force field obtained by the plasma simulation, and the effects of the flow field obtained by the Navier-Stokes simulation is taken into account in the plasma simulation. As a result, although the flow velocity induced by the DBD plasma actuator is low(up to 10m/s), the discharge plasmadynamics is affected by the induced flow field. It is considered that the convection of plasma ions by the induced flow affects the discharge characteristics, especially in the positive-going voltage half cycle.

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Modeling of minute plasma formation is of great importance around electrodes of a plasma actuator(PA) utilizing dielectric barrier discharge(DBD)with a relatively low computational cost. Although electrons need some distance to acquire sufficient energy causing impact ionization, such a transient phenomenon cannot be described in a conventional fluid model because of local field approximation. In order to simulate appropriate discharge process in the DBD-PA, a hybrid code coupling with a particle model was constructed, which treats high-density region as the fluid model but high electric field region as the particle model. The hybrid simulation reproduced spreading of the high-density region from the exposed electrode for the positively biased case as well as the full-particle simulation.

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In present study, the performance of plasma actuator for aerodynamic control was evaluated by means of numerical analysis using RANS and the Suzen model. The flow field of Semi-Circular Cylinder using plasma actuator was analyzed and compared to the data from wind tunnel experiment. As a result, the flow field and the drag reduction obtained from the numerical simulation were in good agreement with the experimental data qualitatively.

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Dielectric barrier discharge(DBD) plasma actuators were applied to the horizontal axis wind turbine to improve the aerodynamic performance. The axis torque and pressure distributions on the wing of the wind turbine were measuremed to evaluate the effect of flow control by plasma actuators. The difference of the flowfields between plasma on and off was also visualized by the tuft and pressure-sensitive paint. These results indicated that plasma actuators could improve the performance of the wind turbine.

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A feedback control system for mitigating periodic flow separation on the NACA0024 airfoil was constructed by using string-type dielectric barrier discharge plasma actuators(string-type DBD-PAs) and fiber Bragg grating flow sensors(FBG-FS). A tangential jet is generated from a string-type DBD-PA placed at 5% chord from the leading edge of the airfoil. An FBG-FS is mounted near root of the cantilever beam interior surface, which detects the vibrations of the cantilever tip forced by wake flow around the trailing edge. The TTL signal to control a HV-RF power supply was output when standard deviations of Bragg wavelength fluctuations(λ_<B'>) are larger than a threshold value(γ), λ_<B'> &ge; γ=0.0028. The durations of flow separation under periodic wall oscillation were significantly reduced by the feedback control system. Tube type DBD-PAs using insulating tubes were also develop to extend utilities of string-type DBD-PAs for practical applications in turbomachineries.

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Newly developed ring-type dielectric barrier discharge(DBD) plasma actuators were used for the active control of the tip leakage flow of an axial-flow turbine rotor. Hot-wire anemometry was used to obtain the turbulence intensity distributions at the annular turbine rotor exit at various input voltages. The plasma lighting in the tip clearance region rotated with the motion of tip of the turbine rotor. The high turbulence intensity region near the tip endwall due to the tip leakage flow was reduced by the active control using the ring-type plasma actuator.

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Plasma Synthetic Jet Actuator(PSJA) is a jet generating device composed of anode-cathode pair and an insulator, and is used for drag reduction and lift augmentation. The synthetic jet is generated by electromagnetic forces produced by AC high voltage between the electrodes. In this paper, we present a Computational Fluid Dynamics(CFD) analysis for the separatio ncontrol of the NACA0015 airfoil using PSJA. In solving the Navier-Stokes equations, we use a two-dimensional body force model based on the Maxwell's equations and Lorenz equation. We obtained the body force distribution and flow velocity distribution around the PSJA. Moreover, the result shows that separation vortex is suppressed by flow control. Simulation result of the value of drag was close to experimental data.

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Plasma actuator has been remarked for active flow control devices that do not contain mechanical moving parts. However, since velocity of induced flow is slow, performance of the plasma actuator was investigated experimentally for variety of parameters including alternating high voltage wave form, electrode thickness and dielectric plate material. The aim of this study is to investigate how design parameter affects the performance improvement of the actuator. Three types of electrode, Line [Span Type], Slot [Stream Type] and Porous [Porous Type], was tested and velocity of induced flow was measured by PIV system. Especially, Span Type electrode showed the best performance at fixed condition.

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An experimental study is performed for multi-passage channel flow with the dielectric barrier discharge plasma actuator(DBD-PA). The multi-passage channel is a reverse flow type, and consists of the five branch passages. The position in which the actuator is installed can be changed in four positions of the outside wall in main channel. The Reynolds number based on the bulk velocity and channel height at the main channel is varied from 600 to 2000. The wave form with voltage of 5 kV and frequency of 2.5 kHz is applied to the electrode of actuator. The wall static pressure is measured, and the pressure loss and flow rate are evaluated. The results show that the pressure loss decreases and the flow rate in each branch passage improves by the effect of induced flow with the plasma actuator. The effect is remarkable in the low Reynolds number region.

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In this study, the concentric DBD plasma actuator was applied the diffusion control of the round jet. The induced flow by the plasma actuator was used as a secondary flow that controls a round jet. It was examined the change of the induced flow and the change of the jet structures by the continuous operating the intermittent operating of the plasma actuator. When it is continuously operated the plasma actuator, the induced flow was annular flow the circumference of the circular jet. And the velocity of the primary jet was increasing by the contraction effect of the induced flow. But, when it is intermittent operated, the induced flow becomes half velocity in the case of continuous operating, and the diffusion of the jet was suppressed.

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To understand the effects of working parameters of the DBD plasma actuator, investigation with a Multi-Objective Design Exploration(MODE) framework is performed. Experiments with a NACA 0015 airfoil fixed to the stall angle of 12 degrees are conducted at Reynolds number of 63,000. The optimization objectives are to maximize the lift coefficient C_l and minimize the power consumption P. The design variables consist of input power parameters. Despite the small population size, an approximate Pareto-optimal front is found. In the objective function space, a region where there exists a linear relationship between C_l and P is found. After a threshold value, the value of C_l seems to saturate. This paper concentrates on this linear region of the objective function space. We use numerical simulation results with similar parameters to several Pareto-optimal experiment cases to compliment our discussion.

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The aim of this study is to introduce streamwise vortex pairs generated by plasma actuator jet into separated shear layer from a circular cylinder. The electrodes of the plasma actuator installed on the surface of the circular cylinder were arranged in the spanwise direction. Induced jets by the actuators collided each other and roll-up into streamwise vortex pairs. Flow visualizations in still air and in the wake region of the cylinder were performed by a high speed camera and PIV analysis. It was found that the streamwise vortex pairs interacted with the vortex structure in separated shear layer from the circular cylinder.

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