Recent works by several groups have pushed direct numerical simulations of turbulent channel flows up to Re_γ ? 4000-5000. However, these values of Re_γ are still insufficient to discuss the multiscale characteristics in a logarithmic layer, and it is necessary to achieve a turbulent state with a wide range of scales. Numerical simulations using polynomial expansions in wall-normal direction often encountered a serious problem caused by their ill-conditioned characteristics. We report here that this problem does not occur by using a appropriate spectral expansions and that we realize turbulent flows at Re_γ up to at 12000.

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Peta-Scale Direct Numerical Simulation (DNS) of wall turbulence are conducted by taking advantage of "K Computer". In the previous DNS of turbulent channel flows, Reynolds number based on the friction velocity and the half height of channel, Re_τ, has reached about 2500 owing to developments of supercomputers and numerical algorithms, while bulk Reynolds number, Re_b, is at least hundred thousand, which is corresponds to Re_τ ? 5000, in real thermal and fluid machines in industrial application. In this study, DNS of turbulent channel flows are carried out at high Reynolds number up to Re_τ = 5000 to reveal dynamic interactions between large- and small-scale structures and construct DNS database as the "standard solution" to verify turbulent model calculation in industrial utilization.

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To verify Large Eddy Simulation (LES) analysis for large scale structures in high-Reynolds number (Re), the LES based on the pseudo-spectral method were adapted for the turbulent channel flow in Re based on the friction velocity and the channel half-width 2000. Total grid numbers of the present LES were a one-eightieth of those of Direct Numerical Simulation (DNS). Compared with DNS database in the same Re condition, results of pre-multiplied spectra and quadrant analysis for large scale structure were quantitatively fitted with each other, except for the contribution of Reynolds stress in inner layer.

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In pipe flow, a streamwise-localized periodic solution of Navier-Stokes equation was discovered by Avila et al (2013). Their solution is an edge state in the sense that it and its stable manifold can a form laminar/turbulent basin boundary. The edge state play a crucial role in the appearance of transient turbulence via a boundary crisis. As Reynolds number increases from that for laminar flow, the occurrence of turbulence and transient turbulence is observed. If the onset of transient turbulence is related with the boundary crisis, there should be close relationship between the edge state and relaminarization. Therefore, we report the association of the process of relaminarization and the flow represented by the edge state.

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Recently, a relation between the mean velocity profile (MVP) and the turbulence intensity distribution have been reported as these have logarithmic portion in the almost same range of distance from the wall. We focus on the relation between MVP and probability density function (PDF) of measured velocity. We found the two characteristic regions in the Kullback-Leibler divergence distribution in the high Reynolds number turbulent boundary layer at Re_τ =7100. These regions have self-similarity of PDF, but each similarity is not equal. So, these regions have different statistic characteristics each other. We found that these regions are connected to two characteristic regions of quasi logarithmic region and classical logarithmic region in MVP.

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In this study, two types of micro-scale hot-film sensors to measure wall shear stress fluctuation are fabricated. The one consists of a polyimide film and silicone rubber as the substrate and the other has a thin silicon wafer as its substrate to increase the frequency response of the sensor. Calibration results show that both of the sensors can measure the time-averaged wall shear stress as expected. However, the frequency response of the sensor whose substrate is silicon wafer is 10 to 100 times better than the other one. In addition, measurement results of the wall shear stress and streamwise velocity fluctuation in the turbulent wall jet indicates that the sensor whose substrate is silicon wafer may be able to measure wall shear stress fluctuation up to 100-1,000 Hz which is enough to discuss the relation between the fluctuating wall shear stress and velocity in this experiment condition.

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Effect of favorable pressure gradient on the structure of turbulent boundary layer has been investigated experimentally. The wall shear stress measurement was made with direct drag balance and mean and turbulent velocity components were obtained from hot-wire measurement with constant temperature anemometers. The new velocity scale for turbulence proposed by considering momentum budget was applied to the similarity in the wall layer. The logarithmic velocity profile normalized with the friction velocity apparently reasonably agrees with the standard log-law in the wide area of the boundary layer, In addition, a modified log-law with the new velocity scale agrees well with experimental results. The new velocity scale reduces difference between normalized streamwise turbulent intensities in zero and favorable pressure gradients.

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Subcritical transition to turbulence in wall-bounded shear flow is known to be characterized in terms of turbulent patches bounded by laminar regions. In circular pipe flow, it is observed that turbulence is localized only in the streamwise direction at marginal Reynolds numbers. Such a structure is a so-called turbulent puff. A turbulent puff is known to decay according to a memoryless process, so that its lifetime has an exponential probability distribution. In rectangular-duct flow, when the aspect ratio is small, i.e., As < 4, a turbulent puff is observed; however, it would exhibit difference from a usual puff as in a pipe. In this study, the decay of a turbulent puff in rectangular-duct flow is measured experimentally by using LDV(Laser Doppler Velocimeter) and PIV(Particle Image Velocimetry). It is found that the survival probability of a turbulent puff is exponential as in pipe flow, but its lifetime is very different from that at the comparable Reynolds number in pipe flow.

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Most of resistance of a transport equipment, such as shipping, is caused by the fluid frictional resistance. Decreasing the fluid frictional resistance may improve the fuel consumption of a transport equipment. The fluid frictional resistance increases if the surface has the roughness. In this research, we measure the velocity profiles in zero-pressure-gradient boundary layer over the two dimensional wave rough surface, and calculate the friction coefficient by using the integrated boundary layer equation. We compare the frictional resistance on rough surface with that on smooth surface. We will discuss how the roughness affects a frictional resistance and a velocity profile.

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Fluid frictional resistance is caused on the surface in the flow. This fluid frictional resistance causes the energy loss, which shares the large part of resistance of a transport equipment, such as shipping. The fluid frictional resistance incleases if the surface has the roughness. It was shown that the coherent structures in turbulent boundary layer affect on turbulence transport and enhance turbulence. In this research, we measure the velocity profiles in zero-pressure-gradient boundary layer over the two dimensional rough surface, and we perform the spectral analysis. We will discuss relation between the resistance increase caused by roughness and the coherent structure.

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Investigation of tripping influence on a turbulent boundary layer was attempted by means of five different tripping devices including classical circular rods and 'V' shape embossment. Spatiotemporal correlation between the wall pressure and the streamwise velocity fluctuations was focused as well as basic statistics such as mean velocity and fluctuation profiles. Measurements were made with a MEMS microphone sensor array that was recently improved. The result shows that pressure distributions capture the local pressure fluctuations due to turbulent disturbances, and its auto-correlation indicates that there exist disturbances of the small spanwise scale. This modified array is expected to reveal the tripping influence on a turbulent boundary layer.

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Disturbances in turbulence are cause and effect of non-linear interactions, so that turbulence itself is known as a non-linear phenomenon. Recently, it was surprisingly found that there exists a linear disturbance excited by a periodic vibration in a two-dimensional turbulent jet. Amplitude of the disturbance normalized by that of the initial disturbance is constant when the initial disturbance amplitude is not considerably strong. In this study, artificial periodical disturbance from a wall surface is introduced to a flat-plate turbulent boundary layer, and development of the disturbance is investigated using a hot wire anemometry. The periodical component, extracted from the streamwise velocity signals with ensemble-average technique, indicates that the existence of a linear disturbance in a turbulent boundary layer, where strong non-linear interaction among turbulent disturbances occurs. It is worth noting that the excited disturbance structure is similar to a hairpin vortex that is generally observed in turbulent shear flows, suggesting that the point-like initial disturbance generates an artificial hairpin vortex.

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Experimental investigation of relationship between flow resistance and a rough wall surface having regular two-dimensional semi-circular ribs was performed. A concentric cylinder device was used to carry out the experiments. This device allows to measure the flow resistance of the inner cylinder directly using a torque meter and the velocity distribution around the ribs by LDV. In the case of Taylor Couette flow, the logarithmic velocity distribution of the hydraulically smooth surface deviate from classical log-law and ? and ? change depend on Reynolds number. The downward shift from mean velocity distribution for smooth wall to that of rough wall, called roughness function (?U1^+) was examined. It was found that the roughness function was independent on the Reynolds number. Finally, ?U1^+ was correlated by frictional coefficient regardless to smooth or rough wall. The correlation formula is usable to another case having different rib geometry and size.

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Asymptotic process of turbulent pipe flow has been investigated experimentally in relaxation process after sudden change in wall roughness from smooth to rough. k-type rough wall was placed at the position where the fully developed smooth pipe flow is established. Mean velocity and turbulent quantities were measured with hot-wire anemometer, and velocity and length scales were obtained from experimental data. Behavior of boundary layer thicknesses are considerably difference between for rough to smooth and smooth to rough. However, development of internal boundary layer thickness and streamwise distance to reach the asymptotic equilibrium situation are roughly the same for smooth to rough and rough to smooth.

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Direct numerical simulations (DNSs) are used to analyze a flat-plate turbulent boundary layer with separation and reattachment. In the present DNSs, the strong blowing and suction are imposed at the upper boundary for producing a large turbulent separation bubble, thus dealing with massive separation. Particular attention is given to Reynolds number dependence in the bubble, streamline curvature effects and similarity to a mixing layer.

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In the transitional channel flow, the large-scale intermittent structure of localized turbulence, which is called turbulent stripe, can be found in the form of stripe arrangement. The structure of the turbulent stripe is laminar-turbulent banded pattern being oblique with respect to the streamwise direction. We performed the direct numerical simulation at the transitional Reynolds numbers and very low-rotation numbers and focused on the turbulent stripe in the plane Poiseuille flow subjected to spanwise system rotation. We captured the turbulent stripe in rotating channel flows and found the augmentation and diminution of the features characterizing the turbulent stripe by the spanwise rotation. The turbulent stripe is enhanced by the Coriolis instability: that is, the magnitude of the spanwise velocity component is intensified, while the quasi-laminar region is widened at low rotation numbers.

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Direct numerical simulations were carried out to study turbulent-laminar pattern in the Poiseuille flow at low Reynolds number. The turbulent-laminar pattern consists of turbulent and quasi-laminar regions that are alternatively arranged in the streamwise direction and form striped pattern. Streamwise vortical structures identified by the second invariant of the deformation tensor are detected and conditionally averaged. As a result, the number of the vortices in the downwind turbulent region was much smaller than that in upwind turbulent region when approaching the wall. Moreover, asymmetry in the numbers of clockwise and counterclockwise vortices occurred in the upwind and downwind turbulent regions. This is due to the existence of the mean spanwise flows in each region.

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Direct numerical simulation was performed for a spatially advancing turbulent flow in a two-dimensional curved channel. The radius ratio of the curved part, α , was set at 0.92, the same as Kobayashi et al.'s experiment. And the friction Reynolds number, Re_<τ0>, was set at 550. Numerically solved mean velocity field showed trends consistent with the experiment. As a result, the validity of the simulation was confirmed. Instantaneous flow field implied that micro-scale structures near the outer wall were related to the birth and growth of large-scale vortices.

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Pressure fluctuations are measured in turbulent boundary layers using a small pressure probe. We find that the measured pressure data are contaminated by the artificial background noise induced by test section and are also affected by the flow boundary conditions. In the presentation, we discuss the effect of solid wall on the pressure data and report the method how to correct the data with the of the wall.

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We measure concentrations of reactive species near the turbulent / non-turbulent (T/NT) interface in a planar liquid jet with a second-order chemical reaction (A + B → R), and investigate the characteristics of chemical reaction and mixing near the T/NT interface. Reactants A and B are premixed into the jet flow and the ambient flow, respectively. We use the optical fiber probe based on the light absorption spectrometry to measure the concentrations of reactive species. We focus on the two interfaces perpendicular to the streamwise direction, which are referred to as leading edge and trailing edge. We derive the conditional statistics conditioned on the distance from the interface. The results show that the conditional mean concentrations and chemical reaction rate have drastic change near the T/NT interface, and the changes near the leading edge are larger than those near the trailing edge.

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Recently, low cost cleaning technique has been demanded to remove small particle that causes quality and yield ratio loss in manufacturing process. In this study, in order to investigate the particle removal characteristics of suction and jet flow in terms of energy saving, we performed particle removal experiment. Furthermore, to enhance the particle detachment, we investigated the effect of surface vibration for particle detachment. For consideration of the experimental results, we analyzed the flow field by using FLUENT. As a result, the particle removal efficiency of jet flow is higher than that of suction flow, even jet flow rate is about 80 percent lower than that of suction flow rate. And the wall shear stress generated by jet flow acts on wide region compare to the suction flow. It was also found that the inertia force due to vibration could assist the particle removal.

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In this study, simultaneous measurement of the temperature at two points with cold-wire sensors is performed at three different downstream locations of a heated plane jet. The measurement apparatus consists of a wind tunnel, a skimmer, a side-wall, and a heater set at the blower intake of the wind tunnel. The temperature of the jet is controlled to become 5 K higher than the ambient fluid. A thin tungsten wire whose diameter is 3.0 μm is used as a sensor and is connected to the self-made constant current circuit. The output of the cold-wire sensor is compensated theoretically to increase the temporal resolution in the measurement. By applying the Karhunen-Loeve (KL) expansion in space and time, the development of the structure in the heated plane jet is investigated from the viewpoint of both space and frequency. Measurement results show that the dominant mode of the fluctuating temperature field in a plane jet expresses and relates to a flapping motion, which is the large-scale coherent vortex structure in the plane jet.

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When a low density fluid is discharged from a round nozzle, side jets that are radial ejections of jet fluid may be generated at the initial region of the jet. The density ratio between the jet fluid and the ambient fluid is a main parameter for the side-jet formation. Since the side-jet formation is also related to the instability of shear layer, it depends on the velocity gradient of the shear layer in the jet. The velocity gradient is evaluated by a ratio of the momentum thickness and the nozzle diameter at the nozzle exit. Compressibility suppresses the instability and the generation of the side jets. The compressibility is evaluated by a Mach number, which is a ratio defined by an issuing velocity of the jet and a sound velocity in the ambient fluid. Influence of these three parameters on the side-jet formation was examined experimentally. Existence of side jets was confirmed by flow visualization using a laser sheet. Moreover, velocity fluctuations in the core region were measured using a hot-wire anemometer during the side-jet formation.

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The authors investigate a self-excited oscillatory phenomenon of a two-dimensional confined jet with a cylinder as a downstream target, especially for both the effects of a streamwise target size a and an aspect ratio. As a result, the authors find that the jet's dominant frequency ?D can be approximately predicted by the proposed empirical formula (Hirata et al., 2011), whenever the jet stably oscillates at various values of the non-dimensional streamwise target size a/b where b denotes the length scale of the jet's breath. The effect of a/b upon the occurrence of the stable jet's oscillation is negligible at a/b≦10. Then, the occurrence can be predicted by the proposed empirical formula (Hirata et al., 2009). On the other hand, at a/b > 10, the a/b effect is not negligible. Furthermore, the authors find that the effects of the aspect ratio h/b upon both the dominant frequency and the occurrence of the stable jet's oscillation are negligible even at such low h/b as 3.

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The three-dimensional time dependent compressible Navier-Stokes equations are numerically solved to study transitional structure in a supersonic round jet at high convective Mach number (M=2.0) using high-order compact upwind schemes. The numerical results indicate that the growth of a pair of helical modes play a significant role for transitional structure and expansion of jet shear layer in a round jet. The growth of a pair of helical modes is responsible for discriminative transitional structure in the downstream of the jet, which yields various decay pattern of the jet centerline velocity.

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The present study clarifies some thrust characteristics of synthetic jets by conducting experiment and numerical simulations. In the paper type synthetic jet thruster is proposed for medical micro-machines or micro air vehicles. It is found that the fluid force and the velocity distribution around a synthetic jet thruster depend on the non -dimensional stroke of the synthetic jet.

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A circular synthetic jet issued from a contraction nozzle was investigated experimentally by using a hot-wire anemometer. The mean and turbulent velocity profiles were measured for a condition of alternating flow at a nozzle exit that is non-dimensional stroke L/d =1.42 and Reynolds number Re =2380. The flow was compared with a circular synthetic jet issued from a circular orifice. The results indicate that the maximum velocity and jet width with the contraction nozzle have different evolution in downstream direction from those with an orifice. These differences are attributed to different lifetime of vortex rings in the synthetic jets. A coaxial annular alternating flow imposed on the circular synthetic jet with a contraction nozzle has almost no effect on the velocity distributions and flow momentum of the synthetic jets.

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A synthetic jet device is a tool for generating a jet, and a synthetic jet actuator is a useful tool for active flow control. The synthetic jet actuators are low operating power, zero-net-mass-flux and very compact devices which have demonstrated their capability in modifying the subsonic flow characteristics for boundary layer flow control. In the present study, the effect of the strength of the synthetic jet on the three-dimensional behavior into a crossflow was investigated. In this experiment, two case of jet-to-crossflow velocity ratio VR were used. The deformation of the vortex ring produced by the synthetic jet into the crossflow is affected by the VR. For VR=0.1, the vortex ring exists at the outer edge of the boundary layer and connected to the wall via a pair of counter-rotating legs (trailing legs). It was confirmed that the boundary layer mixing was promoted for VR=0.1 in contrast to the case of VR=1.0.

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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 order to catch the flow feature the flow visualization was performed by the LIF method. And the velocity measurements of the jet flow issuing from the pentagonal duct with and without the synthetic jet were also carried out using the X-type hot wire sensors and the constant temperature anemometer. 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 clarified that the jet width with synthetic jet becomes large, comparing with that of the jet without one. Moreover it has been also found that the jet is induced by the synthetic jet.

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The present study attempts to clarify flow characteristic in a synthetic jet by a discrete vortex method, particularly focusing on the streamwise mean velocity along the centerline of jets. The onset condition of the synthetic jet was simulated reasonably and depends on the normalized stroke length. The streamwise mean velocity distributions along the centerline of jets agree quantitatively well with the experimental results. The acceleration region, where the streamwise velocity is increasing partially, was observed downstream of slot lips. This is caused by the reductions of the decreasing rate of the induced velocity from the shedding circulations and the increasing rate of the induced velocity from the wall circulations. The upstream streamwise mean velocity is induced from the wall and shedding circulations and the downstream streamwise velocity is mostly supplied from the shedding circulations.

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It is interesting to study flow field around a moving body and flow force acting on it. Studies on vortex flow and vortex structure have been conducted actively. Here are introductions on two kinds of vortex flows around moving boundaries, one of which is experimental results on motion of vorticies around an elastic airfoil surface and the its wake flow as an example of external flow. Another of which is an example of internal flow that is an effective usage of vorticity as a parameter to characterize flow condition. Simulation results on internal flow in a piston head chamber of an oil-hydraulic cylinder show that there are characteristic two kinds of flow patterns, three-dimensional vortex flow pattern and one-dimensional parallel flow pattern.

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It is important to understand and control the wake structure behind three dimensional bluff bodies for various engineering applications. The purpose of this study is to investigate the effect of disturbances on the wake structure behind a circular disk. Small attack angle of the circular disk was added as a static disturbance. Also the plasma jet generated by a dielectric barrier discharge (DBD) plasma actuator was used as a dynamic disturbance. Mean velocities of streamwise, circumferential and radial direction were measured by X-type hot wire probe. Wake structure behind a circular disk was educed from these three velocity components.

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This study investigated the use of a coaxial dielectric barrier discharge plasma actuator at a nozzle exit for jet diffusion control. In order to achieve enhanced mixing of the primary jet flow, the influence of the input voltage and frequency to the plasma actuator was examined. Intermittent control using the plasma actuator was also attempted by varying the driving frequency and the duty ratio. Based on the results of a PIV analysis, the optimum conditions for jet diffusion control were found to be a driving frequency that matched the preferred frequency and a duty ratio at 50%.

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We have developed new multi-sensor hot wire probe in order to measure all components of velocity gradient simultaneously. Simultaneous measurement of all components of velocity gradient is important for understanding dynamics of non-linear energy transfer. Our probe uses less sensors (8 wires) than the previously proposed 12-sensor probe so that size of probe can be more compact. The new probe was tested against wake of circular cylinder.

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The PIV-based evaluation of pressure field and the direct single-point measurement by a miniature static-pressure probe (SP-probe) are combined for further improvement in the velocity-pressure correlation measurement.In order to improve the signal-to-noise ratio of the PIV-based pressure evaluation, the proper orthogonal decomposition (POD) was applied to the pressure gradient evaluated from the PIV results, and the pressure signals directly measured by the SP-probe was used as a reference to determine the number of POD modes to be used in the pressure evaluation. Fluctuating pressure obtained by the present method was in good agreement with that directly measured by the pressure probe, and the improvement was also observed in the velocity-pressure correlation measurement.

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In turbulent mixing of liquid, mixing takes place even in a smaller scale than the Kolomogorov length scale,because of high Schmidt number. In the present study, nearly isotropic turbulence at low Reynolds number was created by a pair of oscillating grid so that the Kolmogorov length can be large. Instantaneous spatial distribution of Rhodamine B concentration under constant mean concentration gradient was obtained by LIF (Laser-Induced Fluorescence) method of which spatial resolution is comparable to the Batchelor length. Noise contained in the measured data is removed by Wavelet decomposition/reconstruction. Some aspect of turbulent mixing within viscous convective range is also observed and further investigation is needed.

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PIV measurement using microbubbles as tracers was attempted. Mean diameter of employed microbubble is around 20?m. Specific gravity of air differs from that of water. It is, therefore, needed to confirm if microbubble can use as tracer. Separated reattaching turbulent flow over a backward-facing (Re=3700) was chosen for test case. Distributions of time-averaged velocity and Reynolds stress obtained using microbubble tracers were generally consistent with those obtained by others. However, careful visualization is needed for turbulent quantity measurement.

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Flow visualization technique using a photochromic dye was applied to investigate the wake vortices behind a rising bubble in a still liquid. A spiropyran dye TMINBP was dissolved in a kerosene-paraffin mixture and the solution was activated by UV-LED projectors. The activated dark blue liquid was subjected to the fluid motion caused by a zigzag rising bubble of which Reynolds number is 255. A hairpin vortex loop shed from a bubble was clearly visualized. A stereo display system was constructed using a commercial stereo display and used to examine the complex three-dimensional vortices in the bubble wake. The concentration distributions of activated dye were deduced from the visualized images using Photochromic Concentration Measuring (PCM) technique. These concentration distributions can be used to evaluate the liquid mass mixing quantitatively. A water-soluble triarylmethane dye 'Acid Violet 19' was also applied to visualize the wake vortices behind an air bubble in water.

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The purpose of the present study is to enhance measurement accuracy of a Single-Tip Optical fiber Probe (S-TOP) in droplet measurement. The S-TOP only with a wedge-shaped tip enables simultaneous measurement of the diameters, velocities and number density of bubbles/droplets. To accurately measure randomly-sprayed droplets, a determination of a touched position by the S-TOP on the droplet surface is essential. In this study, we focused on a characteristic peak (a post-signal) contained in an output signal of the S-TOP. First, We computationally clarified the post-signal characteristics; why and how the peak appears. Basically, the post-signal intensively appears when the S-TOP penetrates a droplet at its pole. Second, we experimentally quantified the relationship between the intensity of the post-signal and the touched position. Then, we established new detection method by using of the post-signal. Consequently, this new detection technique successfully improved the accuracy of the S-TOP droplet measurement.

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The unsteady three-dimensional flow in the junction of circular cylinder and end wall has been investigated experimentally by the moving visualization and PIV measurement. The relative boundary layer thickness ?/d defined as the ratio of the laminar boundary layer thickness against the cylinder diameter was varied widely under the Reynolds number Re=1000. As the results, the three-dimensional flow includes the streamwise vortices near the end wall. In the case of large ?/d there cannot exist Kantian vortex shedding in the three-dimensional flow. But the case of small ?/d, the streamwise vortices are affected by Karman vortex shedding.

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Wake flow behind a permeable disk is visualized, which phenomenologically simulates far-wake aerodynamic characteristics of a horizontal axis wind turbine. Smoke wire method and hot wire anemometer are used to evaluate periodic fluctuation of the flow in the region from 5 to 25 times the disk diameter downstream to the permeable disk. The experiment has shown that there causes a significant three-dimensional spiral-like vortical fluctuation that long persists downstream within the wake. Decrease in solidity of the permeable disk, thus, increase in aerodynamic permeability of the wind turbine, lowers Strouhal number for primary frequency of the velocity fluctuation and decreases the time averaged velocity and turbulence intensity of wake behind the disk.

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There are two types of vertical axis wind turbine, drag-type and lift-type. The drag-type has a small starting torque, but its peripheral velocity does not exceed the wind velocity. As for the lift-type, its peripheral velocity exceeds the wind velocity, but starting torque is large. A hybrid vertical axis wind turbine that has both these advantages was examined in this study. The blade cross-section that has been specially designed for the hybrid vertical axis wind turbine was proposed. Aerodynamic force generated by this blade was evaluated by wind tunnel experiments and numerical simulation in range of 9000<Re<120000. Results obtained this examination shows suppress of separation and generation of lift force in adverse wind condition, which results in improvement of blade performance.

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The purpose of this study is to understand the wake characteristic of two parallel flat plates separated by narrow space. The vortex formation process in either case of "overshoot" or not was shown by using the phase average technique. As the result, it was found that maximum vorticity during the vortex formation process increases temporarily.

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The flow field around the butterfly wing becomes a complicated vortex flow structure. This is because the elastic deformations of the wings and changes in the flow field have significant bi-directional impacts, and the fluid structure interactions are strong. Moreover, the vortex flow and its dynamic behavior generated by the flapping wings of the butterfly are expected to be important for generating the aerodynamic forces required for flight. In the present study, we attempt to clarify the relationship between the vortex ring over the wing and the dynamic lift generated by the flapping wing. We measured the dynamic forces of the flapping butterflies. Moreover, we predicted the dynamic lift generated by the butterfly wing using the circulation of the vortex ring and compared predicted lift with that measured directly.

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In recent years, the co-generation is expected from the viewpoint of utilization of the energy, The leading role of the co-generation is a heat exchanger that is very important equipment to transfer heat between high and low temperature fluid. The fluid used for cogeneration includes a lot of impurities and it is a problem that impurities deposit in a heat exchanger.In order to investigate the deposition in the heat exchanger of the co-generation,, experimental and numerical analysis are eemployed in this study. For the computation of the deposition, the continuum assumption of the many particles is employed to compute wall shear stress, and it was applied in combination with the continuity of particles volume. As the results of this study, it is clear that the position of the deposition is correspond to the high pressure region.

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The vortex generator of the trapezoidal shape fin is mounted on the bottom wall of the channel, their angles with respect to main flow are taken to 30?, 45? and 60? and their inclination angle 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 and velocity distribution are compared with the various VG conditions. In the rectangular channel, the effect of heat transfer enhancement with the trapezoidal shape fin is higher performance than with the delta shape one.

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The mixing phenomena of a density stratified fluid by a 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 2500, and the salt density ranges from 1 to 4 percent. This study classifies the jet behavior into three patterns according to 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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To control the mixing and diffusion of the kinetic momentum in an axisymmetric turbulent jet, 6 vortex generating prominences called Vortex Generators (VGs) whose shape is half delta-wing and can generate longitudinal vortices to the streamwise direction, are applied and its effect is experimentally investigated. VGs are mounted around exit of the axisymmetric jet and their motions can be controlled independently by computer programing. In this study, VGs are operated in two active-control modes beside the passive control mode (i.e. without moving) mode: in the first active-control mode, all the VGs are oscillated radially in the same phase (Axisymmetric mode) and in the first activecontrol mode, three VGs in the opposite side to the vertical section passing through the jet centerline are put in and out to the shear layer at the nozzle exit of the jet (Alternating mode). Experimental results show that all active control modes suppress the entrainment of the ambient fluid into the turbulent jet by the change of entrainment process of the ambient fluid in the jet. It is also shown that the passive-control mode enhances the mixing near the exit.

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Variable inlet guide vanes (IGV), which are a type of swirling flow generator, are installed at the inlet of centrifugal compressors to reduce the inlet Mach number of the rotor blades. However, it is known that the flow instabilities occurs downstream of IGV. In this study, the circular cylinders with tangential blowing are applied as guide vanes to generate the swirling flow. The flow instabilities downstream of IGV / circulation cylinders with tangential blowing are investigated by conducting experiment and performing numerical simulation. Unsteady flow characteristics downstream of them are discussed.

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Active control of rectangular jet has been attempted to manipulate the vortex shedding interval in the major shear layer. We observed vortex structure produced in an excited jet issuing from the nozzle of aspect ratio of 15. Jet characteristics strongly depend on the vortex structure in the shear layer. It was remarkably observed that the jet spreads more widely in the minor direction and shrinks more greatly in the major direction by the asymmetric excitation than that of the natural jet and by the symmetric excitation. The flow deformation process is clarified by flow visualization. As a result, tilting-link vortex was observed for the asymmetric excitation. It plays an important role for mixing and diffusion of the excited rectangular jet. The jet spreading is attributed to the tilting alignment of the vortex ring, and the jet contraction in the minor direction is due to the self-induced deformation of the rectangular vortex ring.

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