We investigate the performance of a DBD plasma actuator to control the aerodynamic characteristics of a flat plate airfoil. To confirm effects of the actuator, the smoke wire method was applied to observe the flow field. The velocity measurements with a hot-wire anemometer were also done to predict the decrease of the airfoil drag. Our results show that maximum drag reduction was 44 percent at the angle of attack of 5 deg.

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The performance of the plasma actuators for wake control and resulting drag reduction is examined and the optimization of the driving conditions of the plasma actuators were carried out by using the robust design method for wake control at high dynamic pressure conditions. The parameter design method that we used is feasible for the optimization of the control variables for flow control, under the situation that has multiple input parameters, requiring robustness, and complexity in flow phenomenon. The result of the design method gives the predicted optimal condition for reduced control parameters and that is confirmed to be robust and stable to the application test.

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The experiment revealed the effect of the enable voltage characteristics on the flow induced by the plasma actuators. Conventionally, the flow was induced only in the direction from the upper electrode to the bottom electrode in general conditions, but it was enable to reverse the flow direction in certain conditions. We controlled the flow by offset voltage. We have experiment under those conditions; normal type, positive-offset type, and negative-offset type. Using the positive-offset, the flow was stronger than normal type. Using the negative-offset, the flow was induced in the direction from the bottom electrode to the upper electrode. The direction of the flow was reverse in the condition of negative offset. Not only the flow velocity but also the flow direction can be controlled by controlling the supplied voltage.

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Velocity distributions of flow produced by dielectric barrier discharge plasma actuators (DBD-PA) were investigated by a particle image velocimetry (PIV) system. Real time measurements of input voltage and current were carried out to optimize input signals and structures of DBD-PA and to minimize the electrical power consumption for realizing the net drag reduction of turbulent flow.

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Magnetorheological fluids(MRF) behave like a Bingham fluid having yield stress which can be rapidly changed in a reversible manner by applying magnetic field, and are anticipated some applications of industrial devices such as damper, a clutch, a brake, and so on. In these applications, one of serious problems is the sedimentation of dispersed particles in the MR fluid in an off-working state. In this research, for the purpose of preventing the particles from settling, an MR fluid composite made of a sponge containing the MR suspension and an MR rubber composite made of the silicone rubber containing ferro-magnetic particles have been developed, and their rheological properties in oscillatory shear mode have been investigated. In addition, a wire tension control system for coil winding using MR sponge composite brake and a damping force-variable damper using the MR sponge composite have been developed, and their performance characteristics have been evaluated.

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Dynamic behaviors of magnetic fluid adsorbed on the permanent magnet subject to vertical vibration or alternating magnetic field were examined with a high speed video camera system. In the experiments, the electrodynamic shaker was used to produce the vertical vibration, and the Helmholtz coil was used to generate the alternating magnetic field. The generation process of capillary jets and droplets of magnetic fluid was observed. It was confirmed that capillary jets of magnetic fluid can be produced both by the vertical vibration and by the alternating magnetic field. The dynamic characteristics of magnetic fluid surface to the vibrations were revealed experimentally.

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In order to solve the various energy problems and the global enhancing temperature in recent years, as one of the various methods, the idea of utilization of a magnetic fluid (MF) has been shown theoretically, and that clarified experimentally. For the phenomena, we can also realize the rotating state of a permanent magnet. We clarified the electric characteristics theoretically and experimentally by utilizing a single electromagnetic induction.

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Accelerated flows are induced between parallel electrodes under an alternating electric field in insulating fluid dispersed dielectric particles. This accelerated flow has many advantages for manufacturing process and bio medical applications. In this study, the effects of the particle cluster length on the inducing mechanism of the accelerated flow are investigated using an experimental measurement and a numerical simulation. The micro particle imaging velocimetry and the micro particle tracking velocimetry were employed for the measurement of the velocity of the flow field and the particles motion. The Eulerian-Lagrangian method was employed to simulate the particles dynamics and the flow structures. As the result, it is clear that the length of the particle cluster near electrode surface has a critical role to induce the accelerated flow.

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In this study, we investigated the effect of the motion direction of the abrasive particles on the polishing inner capillary walls by MCF (Magnetic Compound Fluid) flow. We used an experimental apparatus for polishing inner capillary wall by controlling the flow rate of MCF and the rotational number of magnetic field. We clarified that the relation between the traces left inner the capillary and the motion direction of the abrasive particles which influence the polishing.

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A magnetic refrigerator is thought, with that the magnetocaloric effect gives the system performance. A model device is considered by taking a reverse cycle of Rosensweig energy converter. The preliminary calculation is conducted for the model device on ideal situation, and reported in the present study

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A TMFD (Tuned Magnetic Fluid Damper) is a dynamic absorber using a magnetic fluid. The TMFD dampens oscillations of structures around natural frequency of the TMFD. A magnetic field of vertical direction changes natural frequency of the TMFD. Thus the TMFD dampens oscillations effectively in wide frequency area by using magnetic field. The natural frequency of the TMFD with a coaxial cylindrical container changes lower than that with a cylindrical container. However, it is found that an iron core in a central hole of the coaxial cylindrical container improves the change of the natural frequency. The effect of the core is studied experimentally.

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It is known that the effect of the boundary edge arises on the various modes in the structure and the generating number of Taylor vortex flows with low aspect ratios. In this study, our purpose is to investigate the method to control a Taylor vortex flow (TVF) with a small aspect ratio by using magnetic fluids. Flow field of magnetic fluid under the magnetic field is investigated by numerical analysis. The numerical model device has a radial ratio of 0.667, aspect ratio of 3 and the gap length between the inner and outer cylinders of 25mm. The magnetic field is applied to the flow field using coils put in electric current located on the outside of the vessel. The flow structure of magnetic fluid is controlled by the optional magnetic field

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Magnetic functional fluids are magnetizable suspensions and they are widely studied for various industrial applications. Physical properties of magnetic functional fluids depend on the properties of suspended magnetic particles. In this report, damping force properties of damper utilizing magnetic functional fluids are investigated experimentally; especially we focus on the effects of mixture ratio of volume fraction of nano-sized magnetic particles to that of micron-sized magnetic particles. When the mixture ratios are different, the damping properties are different even if the total volume fractions are equal.

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In the present study, flow structure behind a sphere falling through aqueous solutions of CTAB/NaSal are examined using a dye visualization and a PIV. Visualized dye patterns indicate that aqueous solutions of CTAB/NaSal forms multi layered structure behind a falling sphere. At relatively low salt concentrations, it is observed that the dye detaches from a sphere with its end moving upward where the velocity of fluid in the wake is in the opposite direction to the sphere sedimentation. On the other hand, at relatively high salt concentrations, these phenomena are not observed and the velocity distribution forms wedge like shear layers. At the sudden acceleration of the sphere during sedimentation, it is observed rapid stretching of dye and rapid increasing of upward velocity inducing strong flow behind a sphere.

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Aqueous solutions of cetylrimethyl ammonium bromide and sodium salicylate form wormlike micelles and show shear-induced structure, which causes the change in rheological properties. When a shear-induced structure occurs, white turbidity appears in a flow channel and viscosity changes depending on it. We researched the time required for the emergence of white turbidity, its moving speed, and their dependence of shear rate. As a result, the required time of the emergence of white turbidity depends on only the shear rate independent of the position of measuring point. On the other hand, the moving speed depends on both the position of measurement point and the shear rate.

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Rheo-optic behavior of the shear -induced structure change of wormlike micelles solution on start-up shear flow was investigated. An aqueous solution of CTAB/NaSal was used as a test fluid and it is known that it exhibits one-mode Maxwell type viscoelasticity and also causes flow-induced structure change by shear. Shear stress and flow birefringence were measured using concentric cylinder flow cell and microscopic observation by high-speed CCD camera was carried out on parallel plate flow cell. The micelles were oriented to the flow direction quickly as seen on birefringence behavior, but the viscosity increase that was related to the SIS occurred slower than the micelles orientation. The strip structure was observed at the time region when the SIS occurred.

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Experimental study on the contribution from the surfactant structure to the shear stress characteristics of drag-reducing cationic surfactant solution has been performed. The contributions from each structure were estimated while the surfactant concentration and the counter-ion molar ratio to the surfactants were widely changed. From the results, it was found that the structure having shortest relaxation time well corresponds to the shear stress characteristics. Form the comparison with the drag reduction occurrence map, the shortest relaxation structure was concluded to be the main cause of drag reduction occurrence.

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Brownian dynamics simulations of polymer/clay nanocomposites were carried out. Oblate spheroid particles were applied as a model of clay such as montmorillonite and polymers were modeled by FENE chains. The Gay-Berne potential was used to model inter-particle forces. The behavior of the particles and rheological properties under simple shear flows were numerically analyzed.

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The dynamic motion of a gas bubble rising in shear-thinning fluids with strong and weak elastic properties is experimentally examined. The effect of both elastic and shear-thinning properties on the bubble motion is discussed. It is shown that the bubble rise motion can be systematically explained using modified Morton and Reynolds numbers based on the effective viscosity, Eotvos and Deborah numbers. It is revealed that the bubble rise speed is largely influenced by the effect of the shear-thinning property, whereas both the elastic and shear-thinning effects govern the shape of bubble.

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Two-dimensional unsteady flows of power-law fluids past a circular cylinder are studied by means of numerical simulation. Effects of the power-law index, n=0.7-1.1, on the drag and the near-field flow pattern are investigated in detail. The Reynolds number based on the freestream velocity and the cylinder diameter is set to be 100. The total drag is found to consistently increase with the power-law index, n, similarly to the previous results of steady flows at lower Reynolds numbers.

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We develop the Pressure-Oscillating Defoaming for removing air bubbles from shear-thinning fluids. When rising velocity of an air bubble is fast, the cusped air bubble can be observed only at the period of the contraction, which is induced by local flow due to the expansion and contraction itself. We think that elastic stresses may play a role for enhancing the rising velocity of the bubble. With a help of flow birefringence technique with CTAB/NaSal solution, we try measuring the stress in the vicinity of a small air bubble under pressure-oscillating field.

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It is known that the rheological properties are significantly changed by their chemical characteristics such as pH in some non-Newtonian fluids. We have recently found chemical recipes involving some non-Newtonian fluids which can change the viscosity by chemical reactions. These include an increase in the viscosity by a very fast reaction between a polyacrylic acid solution and a base solution, and a decrease in the viscosity by a very fast reaction between a sodium polyacrylate solution and an acid solution. We have succeeded in experimental investigations on a reacting liquid flow involving changes in the viscosity by means of the chemical recipes.

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Effects of ionic species on flow behavior of aqueous solutions of polyacrylamide (PAM) were experimentally investigated. Elastic property of PAM solution is transiently increased by addition of Fe^<3+> solution and then it is decreased to initial value. In order to elucidate this phenomenon, we investigated the Weissenberg effect of the solution. The phenomenon was explained by the interaction between Fe^<3+> and PAM solution.

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We report various types of coherent structures in suspensions of spherical particles swimming in a suspension. We solve the fluid dynamics precisely from far-field hydrodynamic interactions to lubrication between two near-contact surfaces. The simulation results clearly illustrate that coherent structures, such as aggregation, meso-scale spatiotemporal motion and band formation, can be generated by purely hydrodynamic interactions.

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The boundary layer theory developed for high Reynolds number Newtonian fluid flow is essentially based on the simplification of the N-S equation using the fact that a lateral dimension of the flow field is much smaller than the longitudinal dimension. Hence, it is applied to non-Newtonian vsicoelastic fluid flows with low Reynolds numbers when the geometry of flow field satisfies the same condition.

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Drag reduction caused by cationic surfactant solutions is considered to be an effective way to reduce the running cost in closed-loop district heating and cooling systems. Conversely, much research has pointed out that heat transfer reduction occurs simultaneously for drag reducing flows. In this study, heat transfer characteristics were measured for drag-reducing additives with two cationic surfactants (Ethoquad O/12 and Ethoquad O/13) using a test loop equipment and a practical air conditioning system. From the results, significant decreases of heat transfer coefficients were observed for drag-reducing additives, however, temperature difference between the inlet and outlet of the test section can not be decreased compared with that of water.

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The most of previous works only showed dependence of viscosity of the magnet fluids on magnetic field. The relationship between magnetic viscoelastic fluids used in this study and magnetic field is not yet studied fully. The measurement was taken by a rheological device, which can measure the rheological characteristic of magnetic viscoelastic fluids on the magnetic field.

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This paper describes the flow phenomena of unvulcanized rubber in pressure molding of oilseals. We conducted experiments and unsteady numerical analysis about these oilseals and investigated the intenal flow. The results of the unsteady numerical analysis represent approximate characteristics of flow phenomena and internal flow in pressure molding of experiments. The results of the unsteady numerical analysis show that shear stress acted when the unvulcanized rubber flowed in narrow channel and the relation of pressure and velocity.

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We have numerical investigated the backflow effect of a nematic liquid crystal between concentric cylinders, using the Leslie-Ericksen continuum theory. When an electric filed is applied between the cylinders, the nematic liquid crystalline flow called the backflow is induced due to the reorientation of the nematic liquid crystalline molecules. For the low curvature of flow channel, the induced backflow profile is anti-symmetric with respect to the center of the channel. As the curvature increase, the profile changes to asymmetric, and finally becomes one-directional. It is also found that the shear stress on the inner cylinder becomes higher with the increase of the curvature.

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We have investigated transient responses in start-up large deformation of smectic-A liquid crystal (8CB) whose yield stress can be controlled with electric field strength and its current type. Shear rate change in the transient behavior with constant stress applied had been measured. Apparent viscosity responses were estimated and those strain dependency was examined. When larger stresses than the yield stress were applied, the viscosity changes were almost corresponded with the strain regardless of the stress applied. In the case of the nearly the same stress with the yield stress, typical response with high constant apparent viscosity was obtained in the small strain region before the large deformation started. Very small deformation and increase in the resistance to deformation had been observed when smaller stress was applied.

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Compression tests of foods were numerically simulated using a finite element method. Since the deformation was large and includes fracture, Arbitrary Lagrangian-Eulerian method was applied to a soft tofu. On the other hand, a tiebreak model was applied to simulate the fractures of a banana and a cookie. A linear plasticity model was used as the rheological model for all foods. Reasonable agreements were obtained on the behaviors of compression and fracture between the simulations and the experiments including the reaction forces on the plunger.

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This report describes experimental results on the supersonic flow phenomena in rectangular ducts which are the models of isolators of cramjet engine, using the pressure-vacuum type Mach 4 supersonic wind tunnel. This investigation shows the effects of duct cross-section aspect ratio and length on the supersonic flow structure in the rectangular ducts by schlieren photographs, duct wall pressure fluctuation measurements and detailed total pressure distribution measurements.

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Shock wave compression prefer to a piston process in the rapidity and the spatial homogeneity on compression of a combustible gas mixture. In the present study, the ignition phenomena by numerical analysis are examined under the interference between a shock wave and disturbance induced due to an obstacle. Hydrogen gas mixture with a dilution [Argon or Nitrogen] are used as fuels which are comparatively advanced with other fuels. There exist some detailed chemical reaction mechanisms for the gas mixture. Used numerical method is the second order semi-implicit MacCormack-TVD scheme.

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A blunt body in hypersonic flow is subjected to severe aerodynamic heating and drag. This is one of the most critical problems of designing the hypersonic vehicles such as Reusable Launch Vehicles(RLV). It is well known that the spiked-nose(aerospike)concept is effective to reduce aerodynamic drag on asymmetric blunt bodies in hypersonic flow. In this study, we investigated the heat flux distribution on a blunt-nosed body with an aerospike in hypersonic flow. The flow field around a blunt-nosed body is calculated by the full Navier-Stokes simulations to compare with the experimental data such as Schlieren photographs and TSP(Temperature Sensitive Paint)images. It was found that the heat flux distributions changes widely with the angle of attack. Moreover, the correlation between heat flux and the flow and the flow field exists due to the shock/shock interaction patterns for various angle-of-attacks.

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In this paper, we experimentally verify a new model to predict the predominant frequency of acoustic oscillations in supersonic flows over a rectangular cavity. This model was developed previously in order to understand why the jump in the predominant frequency occurred when the length-to-depth ratio of the cavity was gradually varied. In the experiment, the target flow is supersonic flows over a rectangular cavity with the inlet Mach number of 1.7. The length-to-depth ration of the cavity is varied by changing the depth with the length constant. The oscillation in pressure is measured by the semiconductor type pressure sensor mounted on the wall downstream of the trailing edge of the cavity. The power spectral density is calculated from the time-dependent pressure signals and then the predominant frequencies are obtained for each cavity depth. Also, the predominant frequencies are calculated by using the model for each experimental condition. The results obtained by using the model are found to agree with the experimental results with respect to both the frequency jump and the variation in frequency with the length-to-depth ratio.

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The interaction of a normal shock wave with a turbulent boundary layer at a low Mach number in a square straight duct is investigated experimentally. Wall static pressures have been measured in the interaction region and flow visualization by the color schlieren system with tricolor filter has been performed to observe a variation of the shock structure by the interaction. It is shown that a weak normal shock wave interacts with a turbulent boundary layer to form a shock train for a large blockage ratio.

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Sonic conductance is an important quantity that represents choked flow rate of compressible fluid through pneumatic fluid power components. This paper analyzes compressible flows with friction(Fanno flows)through straight pipes, and makes clear the correlation between sonic conductance and total pressure loss in Fanno flows.

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A laser-induced micro shock wave was observed with shadowgraphic technique. The shock wave generated on a metal surface due to laser irradiation. In this paper, a micro shock wave was induced within a low intensity energy region in the vicinity of the energy threshold. Shadowgraphic images were acquired within 1μs from laser irradiation. Under this experimental condition, in the case of in irradiation laser intensity of I_0=250GW/m^2 or less, the shock wave 1μs from laser irradiation was not able to be observed. Energy conversion efficiency was estimated by ratio of the shock wave energy to input laser energy. Here, the shock wave energy was estimated by self-similar analysis. The energy conversion efficiency increases in proportion to irradiation laser intensity.

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When the underexpanded supersonic jet impinges on the obstacle, the self-induced flow oscillation occurs at the specific condition and this oscillation is related with the noise problems of aeronautical and other industrial engineering. The investigation for the self-induced flow oscillation was carried out during and the underexpanded supersonic jet impinged with the cylindrical body. The wave structure formed in the flowfield and the pressure change with time at the cylindrical body were obtained by the experiment. From the result of this investigation, it is cleared that oscillated shock wave differs by the pressure ratio of flowfield and the peak frequency of an oscillation depend on the pressure ratio of flowfield.

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The numerical result of supersonic jet is non-dimensionalized by the nozzle e exit diameter for analysis of jet structure. In recently, the micro-nozzle as like milli-m or micro-m size is used in industrial engineering. In this case, it seems that whether to compose the similarity of jet structure may be cleared so that this paper aims to clear the influence of the nozzle diameter for the structure of underexpanded supersonic jet by numerical analysis. In the numerical calculation, the nozzle diameter decreases from 12 mm and the jet structure, the location and diameter of Mach disk, the sonic line and the boundary layer in nozzle are analyzed in this study.

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An underexpanded jet is utilized in industries to cool a heated material, to blow the dust away from the product and so on. When the jet impinges on such objects, the jet oscillates and a noise radiates from it. Thus, it is necessary that flow patterns of the jet at impingement, which greatly affect those efficiency, is analyzed in detail. In this paper, the underexpanded jet impinges normally on a thin plate. Behaviour of the jet is expected by analyzing a vibration of the plate at different nozzle-plate spacings. As a result, one of the jet flow patterns, a lateral oscillation mode, was observed and the oscillation plane of the jet was found to rotate.

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In order to control the vertical structure in the wake of a sphere, the active flow technique using acoustic excitation was utilized. The vertical structure depend on the intensity of excitation, frequency and excitation mode. The structures depended on not only the frequency, but also the acoustic mode. The excitation mode is the most important parameter to control of the wake structure of a sphere. In the natural condition, both of helical and alternative modes are existed. The wake structure can be controlled with the acoustic excitation. Moreover, the acoustic excitation seems to be effective for the flow control with small energy.

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In order to clarify the generation mechanism of aerodynamic sound from a cavity, aerodynamic sound and flow fields around a cavity were measured with a high-speed flow visualization system. In this experiment, we investigated flow pattern around downstream edge of the cavity in sharp edge and round edge. The flow visualization results showed that the amplitude of sound pressure become maximum when the center of the vortex core through the edge. At that time, the vortex core strongly deformed. On the other hand, the vortex deformation is slow in the case of round edge cavity. Then the sound pressure level was smaller than that of the sharp edge. In the case of the large curvature edge, the formation region of vortex core moved to downstream direction and then undeveloped vortex collided with the edge. As a result, aerodynamic sound become much smaller than that of the original cavity.

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The three dimensional structure of the wake vortex was investigated in relating to the aeolian tone from the inclined flat blade, which is installed in the uniform flow from zero to thirty degree of the inclined angles with upper and lower wall. It was pointed out that the aeolian tone becomes large at ten degree of the inclined. At small inclined angle, the formation of wake vortex is occurred at the same time in wide span location. The scale of the wake vortex in span direction becomes large at small inclined angles. The span wise correlation of the wake vortex at zero inclined angle is only restricted near the position of the vortex formation, but the correlation at small inclined angle is spread in span direction and becomes large. At the large inclined angle, the formation of wake vortex starts near the lower corner of the blade and this is traveled toward to the upper side of the blade. The structure of the wake vortex is weak and does not have strong periodicity. Then the correlation of wake vortex becomes small with the inclined angle.

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An experimental analysis was done about the influence of the unsteady flow on the aerodynamic noise of the ring fan. The relative velocity of the ring fan was decelerated than the current propeller fan, because the swirl of the blade tip vortex is controlled by the shroud assembly at the tip side. From results of this experiment, it clarified that the aerodynamic noise of the ring fan is decreased by the decelerating of the relative velocity in the wake and the weakened potential of the wake vortex.

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