This study deals with the hybrid wind tunnel which combines wind tunnel experiment and numerical simulation to obtain the exact and detailed information of real flows. The hybrid wind tunnel based on the observer theory utilizes partial information of the real flow from pressure measurement for the numerical simulation through a feedback loop to overcome the difficulty of specifying exact boundary or initial conditions as well as the effect of modeling error. In previous two-dimensional analyses on the hybrid wind tunnel, the difference between computation and experiment in regard to perturbation velocity increased with the computational grid of a high resolution due to the inappropriateness of the two-dimensional model. In this paper, three-dimensional analyses with three grid systems of different resolutions are performed on the hybrid wind tunnel for a fundamental flow with the Karman vortex street behind a square cylinder. The reproducibility of a velocity field on the hybrid wind tunnel is improved in three-dimensional analysis by using the high resolution grid system. In addition, three-dimensional analysis with the coarse grid system on the hybrid wind tunnel effectively reduces the error due to the insufficient grid resolution for ordinary numerical simulation.

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The present authors have been investigated a canard type roadable aircraft fixed an inflatable ring wing as for the future vehicle. In this research, two-dimensional inflatable wing was tested using wind tunnel to predict an effect of a deformation of wing on aerodynamics forces. Furthermore, CFD simulation was conducted to predict the detail of flow field around an inflatable wing. It is clarified that the lift and drag of a deformed wing increase than non-deformed wing and an increasing rate of drag by a wing deformation is higher than lift.

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A Modulation of turbulence characteristic induced by bubbles in nearly homogeneous isotopic turbulence was experimentally studied. Turbulence and bubbles were generated by an oscillating grid system and bubbles generator using an audio speaker, respectively. Liquid motion was measured via PIV. Turbulence structure was discussed on the basis of an energy spectrum. At first, we confirmed that the Kolomogorov -5/3 law is observed in the homogeneous isotropic turbulence field. Second, it was confirmed that a relation of energy spectrum in two cases, Condition-B (in the case of injection bubbles in the quiescent fluid) and Condition-OB (in the case of injection bubbles in the Grid turbulence flow), changes due to the grid condition (grating spaces and bars) in the spectral space.

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The two-dimensional jet diffusion in liquid-phase has been investigated experimentally in order to clarify an effect of turbulent mixing on chemical reactions. The chemical reaction used in this study is the second-order reaction (R+B→S). The concentrations of all the species (R, B, and S) have been measured simultaneously by the combined technique of the light absorption spectrometric method with an optical fiber probe and the conserved scalar theory. It was found that the profiles of mean concentration and r.m.s. value of reactant R are close to the frozen limit in the present condition. However, the mean concentration of reactant B decreases and the r.m.s. value becomes large in the downstream direction as compared with the frozen limit by the effect of chemical reaction.

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The fluid catalytic cracking process is the most important technology to convert low-value heavy ends of crude oils into more valuable blended stocks, such as commercial gasoline. Fluid catalytic cracking catalysts are used to produce high-octane gasoline from residual oil by the contact cracking process in the petroleum refinery. The key point to producing high-quality gasoline from residual oil is uniform fluidization at the mixing point. The sensor for capacitance CT is designed to visualize the powder concentration in the process of mixing air and FCC catalysts in a vertical pipeline. The relationship between the air-catalyst parameter condition and the powder distribution is analyzed in detail.

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The Multi-scale method for the supercritical combustion flow under high pressure is applied to understand the thermo-physical phenomena. The present study is focused on the construction of thermo-physical properties including as some radicals as well as H2 and O_2, equation of state (EOS), and chemical reaction model to apply on the super- critical state. The thermo-physical property and EOS are calculated by the molecular dynamics simulations and quantum dynamics simulations. The chemical reaction model is constructed by using CHEMKIN in order to estimate the reaction rate constant under high pressure conditions.

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Recently, various shapes of conducting polymer soft actuators attract the attention of many researchers. In our study, the authors have proposed a tube type soft actuator based on the conducting polymer and the micro pump driven by tube type conducting polymer soft actuator. Upon oxidization and reduction, the conducting polymers change the physical properties as swelling or shrinking. The change of the dimension is induced by the electrochemical cycle, which is called electrochemomechanical deformation and can be utilized as soft actuators and artificial muscles We have prepared the tube type conducting polymer soft actuator using Polypyrrole and TBATFSI. The top of the tube type conducting polymer actuator with insulating tape on both sides of the soft actuator open and close by electrochemical reduction and oxidation. Moreover, we have built up the micro pump using tube type conducting polymer soft actuator as a driving source. The oscillation volume of the micro pump can be adjusted in the range of 15〜32 [μl/min]

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This paper describes the development of microcapsules for shock wave drug delivery systems (DDS). Especially, capsule structure and driving force is investigated. In the first step, the neutrophil based capsule is made for DDS instead of polymer membrane capsule. When some part in our body inflames, materials, whose name is cytokine, are released. These materials pull neutrophil, one of white blood cell, toward inflamed part. It is said that neutrophils are moved to inflamed part by gradient of cytokine concentration that is called chemotoxis. This mechanism is immune mechanism. If we can control chemotasis of neutrophil, it follows the development of application in the fields of immunity and drug delivery system. In the second step, the motion of neutrophil by gradient of cytokine is investigated.

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Flow structures passing through an inclined tube and inclined tube banks were investigared in the present study. Experiments were carried out using acrylic rectanglar water tunnel. Re is ranged from 2000 to 10000. Flow were visualized by minute particles and recorded by a high-speed video camera. The particle image velocimetry were carried out, and velocity fields are obtained. As a result, three typical regions of time-averaged streamwise velocity were observed in the wake region of an inclined tube. These velocity regions are considered to be caused by secondary flows that appeard in the wake region and both sides of the tube. Moreover, these secondary flows are considered to be caused by inclined vortex shedding.

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The torsion parameter β_0 (β_0=γ/(2δ)^<1/2.,γ:dimensionless torsion, δ:dimensionless curvature) is experimentally obtained for which value the critical Reynolds number Rec is smallest for helical pipe flows. The mean velocity distributions and the turbulent intensities in helical pipe flows are observed by use of a X-type hot-wire anemometer in the range of the Reynolds number from 200 to 13000. It is found that Rec first decreases as β_0 increases before β_0 reaches about 1.4, and then it increases as β_0 increases. The minimum of Rec is experimentally found to be about 400 at β_01.4.

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Effects of the distance between an axial cooling fan and its air-cooled target on heat transfer characteristic of cooling fan were investigated experimentally and numerically. A heated plate, simulating the surface to be cooled, is installed at the downstream of the cooling fan. Temperature on the heat transfer surface is measured using thermocouples to evaluate heat transfer effects among the different distances. Detailed flow measurement is performed using a slant hot-wire probe to clarify time-resolved flow structure as well as turbulent flow characteristics contained in the near-wall flow field. These experimental results are compared with the numerical ones, obtained by using a commercial CFD code CFX10.0 for a three-dimensioned unsteady prediction. These aero-thermal results indicate that the important role of the fan-surface distance in terms of flow rate and cooling performance.

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It is quite usual that the small axial flow fan used for PCs is installed in a narrow space. In such cases the fan performance and flow field are supposed to be different from those design conditions. In addition, influences that obstacles upstream and downstream of the fan give to the fan performance are not well understood. In this study, we measure the flow field and performance of the fan used under realistic conditions. Furthermore, we compare calculated results with the experiment results. According to the measurement, some changes are observed in the performance and flow field of the fan used at the narrow space.

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To improve the measuring accuracy of the ultrasonic flowmeter for gaseous hydrogen, the effect of flow channel geometry on the internal flow has been investigated. The internal flow fields were analyzed by numerical analysis, verified by experiments using PIV. For the same flow rate, the distribution of the axial velocity has no difference between the straight and exponential channel models. For the same channel model, the velocity distributions in the cross-sectional and streamwise directions are independent of the channel diameter.

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In a process gas piping system of a chemical plant with a centrifugal compressor, many instruments such as control valves, temperature, pressure, and flow rate measuring instruments are installed under high pressure and high flow rate. It's difficult to identify the vibration sources and the highly affected parts in the centrifugal compressor, the control valves, a variety of instruments, or support device. This paper shows the trouble and countermeasures for these complex vibrations.

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We experimentally and computationally investigated aerodynamic performance and acoustic noise characteristics of a centrifugal blower in a narrow space. This blower had a wall near the suction side. The experimental results revealed that the pressure rise was lower and the noise level was higher than for a blower equipped in a free space. The computational results revealed that the inlet flow distribution was larger equipped in a narrow space and flow separation occurred on the edge of the bellmouth. The inlet flow distribution has increased maximum relative velocity in the fan. We concluded from these results indicate that the inlet flow characteristics strongly affect the aerodynamic performance and acoustic noise level of blowers equipped in a narrow space.

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The wake oscillation of a circular cylinder, which is placed near a plane boundary, with tangential blowing from a surface slot is investigated experimentally at Reynolds number Re=2.7×10^44. The time-mean surface pressure measurements on the circular cylinder, flow visualizations and velocity fluctuation measurements were carried out for various jet momentum coefficient, C_μ, and clearances between the circular cylinder and the plane boundary changed. Based on these experiments it is found that periodic velocity fluctuation, which is associated with vortex shedding (Karman vortices), is suppressed by the tangential blowing. However, in the case of the cylinder placed near the plane boundary, the reverse flow occurs in the clearance between the cylinder and the plane boundary, in particular C_μ increases. The level of flow unsteadiness naturally increases.

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Water flows in a fluidic oscillator with a target were simulated numerically for Reynolds number range from 35 to 699. The fluidic oscillator consists of a nozzle, a short diffuser, a target and two feedback channels. The possible application of this oscillator is a miniature liquid mixer. It is found that the simulated flow patterns, oscillation frequency and minimum Reynolds number agree well with the previous experimental study. The simulated jet displacement is correlated well with pressure difference in control ports. It is also observed that the deflected jet impinges on a rear port of feedback channel and the resulting high-pressure accelerates flow in the feedback channel. Based on the velocities and pressures in the control ports, the flow mechanism of the oscillation is explained.

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A steam control valve is used to control the steam flow from a steam generator to a turbine in power plants. The flow field in the steam control valve is usually complex and transonic. A flow-induced vibration of the valve can occur and may cause unexpected shutdown. An experimental and numerical study is conducted to clarify the characteristics of the flow in the steam control valve. In the present study, characteristics of the flow fluctuation around the valve, a pressure fluctuation caused by acoustic resonance and a fluid structure coupled vibration of the valve head has been investigated. The experimental results show the operating condition where these vibrations occur. The numerical results show detailed flow fields and causes of them.

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Stem cell culture has an impressive influence for curing a variety of diseases. This paper presents a fundamental flow analysis in an bioreactor for the stem cell culture for scaling up and mass production. We carried out the flow visualization and Ply measurement in order to inspect the mean stream and its turbulence. It was found that the Kolmogorov's scale was a key factor for control an agglomerate diameter of a cell in the bioreactor. Therefore, we analyzed flow configuration in the rotating disk bioreactor to reveal relation between the main vortex and cell growth.

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An experimental study was performed for the flow in a modeled hydraulic headbox of paper making machines. The turbulent boundary layer generated on the partition plate in the dispartion part and the wakes formed downstream of the plates were investigated by using the flow visualization technique of a smoke wire method and by hot-wire measurements. Those controls were explored for several kinds of test channels and the plates that differ in convergence and trailing edge shape, respectively. As a result, the rectification by contracting the channel is effective in making the distribution of the average velocity uniform and in attenuating and unifying the turbulence intensity. Furthermore, the unifomalization of the average velocity is high for the trailing edges of a tapered and a wavy shape, while the homogeneity of the turbulence intensity is excellent for the tapered edge.

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All the region of circulatory system can not be analyzed using computational fluid dynamics (CFD), because the structure is so complicated and the analysis region is restricted by computer memory. In order to analyze the flows, it is necessary to simplifi and investigate the complicated network structure of vascular system quantitatively. We showed quantification of complicated structure using fractal dimension in our previous studies. This paper describes the relation between the flow field and the fractal dimension, and the computation scheme of volume flow distribution using box-counting method. One-dimensional model of cerebral vessel with considering tree structure was established.

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Continuous cost reduction is required in the car industry. In the paint drying process during production, impurities which adhered on car body must be removed and they cause cost increase. To study the gas and particle flow in the drying furnace, CFD is a strong tool because experimental approach is difficult due to the high temperature. Particle flow and adhesion were simulated and predicted depending on particle size and density.

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The air-water bubbly flow around a hydrofoil is simulated with the vortex method proposed by the authors in a prior paper. A hydrofoil of NACA4412 with a chord length 100mm is mounted at the angle of attack of 10 degree in an air- water bubbly flow. The Reynolds number is 2.5×10^5, the bubble diameter is 1 mm, and the volumetric flow ratio of bubble to whole fluid is 0.048. The simulation demonstrates that the two-phase flow features around the hydrofoil are successfully captured and that the vortex method is indeed applicable to the bubbly flow analysis around a hydrofoil.

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High temperature nitrogen plasma flow was generated by an arc-heated wind tunnel. The effect of the plasma flow on composition and a property of metal materials were investigated. In this paper, nitriding of carbon steel, which is one of techniques for surface hardening was undertaken by the plasma flow and a change of metal properties with or without shock-shock interaction was analyzed by a hardness meter. In addition, hardness of metal materials due to the pattern of shock-shock interaction was investigated.

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This paper deals with the investigation of wake-disturbed boundary layers on a flat-plate model with an elliptic leading edge. The wakes are generated by the transversely moving bars in front of the test model. The main focus of this paper is how the wake passage affects the transitional behavior of the boundary layer under the influence of favorable and adverse pressure gradients. The flow accelerating and decelerating devices simulate the pressure gradients on the suction surface of the turbine rotor or nozzle. A spoked-wheel-type wake generator is used to simulate the unsteady flow field over the suction surface of a turbine rotor or nozzle by changing the direction of the rotation of the wake-generator. Detailed boundary layer measurements are performed by use of hot-wire anemometry, which allows analysis of the raw signals of the velocity, ensemble-averaged velocity, turbulence intensity and time-averaged intermittency factors. It is found that the effect of the calmed region, which is the laminar-like flow occurring immediately behind a turbulent spot, delays the transition in the region between wakes.

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Flow separation is an undesirable phenomenon because it causes the large energy losses in a fluid machinery and stall on airfoils. The vortex generator jet (VGJs) method is an active control of flow separation and can achieve the adaptive control by properly adjusting the jet speed. Jets in a crossflow provide complex interacting flow that contains many vortices. It is important that the details of near fields of the jet are clarified for issuing the jet into a crossflow. For the VGJ method, the suppression effect on flow separation was affected by the jet orifice shape. In this study, structural features resulting from the interaction of a non-circular jet issuing transversely into a crossflow were described with the flow visualization technique. The formation and behavior of the vortices in the wake were affected by the jet orifice shape. For the T shaped jet orifice, there is a significant difference between the strengths of positive and negative vortices, and the wake vortices indicate the different structure in the spanwise direction.

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A new subgrid-scale (SGS) one-equation model of the large eddy simulation (LES) for compressible turbulent flows, which includes the coherent structure model function suggested by Kobayashi, is proposed. Using the direct numerical simulation (DNS) data of the compressible turbulent mixing layer, a priori test for the model expression is performed. In the LES, we show that the predictions of the SGS model reproduce the DNS results.

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The understanding of the physics of flapping flight has long been limited due to the obvious experimental difficulties in studying the flow field around real living thing. In this study the three-dimensional numerical simulation based on non-inertia reference was performed. The object motion is computed by the momentum equation using pressure calculated by the flow computation. And two-dimensional velocity field around the flat plate swinging of pendulum was measured quantitatively. We show that the data can be used for quantitative studies, such as lift and drag prediction.

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Micro-Air-Vehicle and micro-flight robot using insect and bird flight mechanisms has been attracting significant attention in recent years. However, flight mechanisms of insects have not been clarified sufficiently. In order to clarify geometric properties of flapping motion on butterflies wing with free flight, bound flight and towing flight we conducted flight observation experiments by a high-speed camera, measured displacement of a butterfly wings using images captured by the camera and transformed into flapping angles and lead-lag angles from the butterfly view. The lead-lag angles are one of the important parameters for free flight, on the other hand, for bound and towing flights, the butterfly changed flapping angles more greatly than lead-lag angles trying to escape from the towing since its legs and body were bound.

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The purpose of this investigation is to develop the flapping-wing micro air vehicles based on dragonflies. We attempted to product mechanical flapper based on dragonflies. The flow fields and aerodynamic force of the mechanical flapper were measured with dynamic PIV system. The flow field around the mechanical flapper was almost the same as that of dragonfly. The leading edge separation and wake capture process can be observed. The aerodynamic force of the mechanical flapper was proportional to the second powers of the flapping frequency. The aerodynamic lifting force of the mechanical flapper was 0.68 times of weight the flapper at the flapping frequency of 37.6 Hz. It corresponded to twice of dragonflies' weight, it therefore indicated that the mechanical flapper generated sufficiently large enough to lift the dragonflies.

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The purpose of this research is to clarify generation mechanism of aerodynamic force of flying insects such as the dragonfly. To understand the mechanism of insect flight is important to develop Micro Air Vehicles (MAV) for rescue inquiry devices of disaster area. The aim of this investigation is a quantitative correlation analysis between vortex structure around a dragonfly and aerodynamic force. Unsteady aerodynamic force and flow field were measured by micro load-cell system and dynamic PIV system. As a result, the continuous vortex tubes were observed such as the U-shaped separation. The topology of the separated flow is almost two dimensional without near wing-tip. When the distance of vortex core was small, the large amounts of aerodynamic forces were generated. The experimental results showed strong interaction between the vortices and wings occurred when the distance of vortex core was almost same as the chord length.

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Aerodynamic forces and moment of a sawtooth leading edge delta wing were experimentally studied in a low-speed wind tunnel. We researched the effects of the sawtooth leading edge on the aerodynamics and the leading edge vortices through the pressure measurement on wing surface. In the result, it was found that the minimum pressure and its location on the wing were different from those of the base delta wing without a sawtooth leading edge. It was owing to the interaction of the primary vortex, namely a leading edge vortex, with the secondary vortex from the sawtooth leading edge. It increased the C_L over 10%

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A compressible bubble-liquid mixture flow model is developed for computing high-speed cavitation flows by coupling a bubble dynamic calculation based on the Two-Fluids Three-Pressure model and a compressible mixture flow procedure. General Navier-Stokes equations for compressible fluid are employed to simulate the flow of two-phase mixture. State equations of liquid and gas phases are adopted and a relation for the mixture density and pressure is derived. As an example, cavitating and no-cavitating flows in a Venturi nozzle are treated and the capability of present model is demonstrated.

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Direct numerical simulation (DNS) for homogeneous turbulent shear flows in the streamwise system rotating is performed. In the turbulence energy, the streamwise rotation effect is smaller than the shear-direction and spanwise ones. In the budget of the Reynolds stress, the rotation term balances with the pressure strain one at the strong rotation case. The streamwise rotation effect has influence on the small-scale motion.

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In this study, SPH (smoothed particle hydrodynamics) simulations have been performed on the jet break-up and impinging jet considering the effect of the surface tension. For the jet break-up simulations, the liquid pillar was broken into multiple droplets due to the surface instability caused by the surface tension, and the effect of the injection velocity corresponded well with experimental results. For the impinging jet simulations, the film thickness of the impinged liquid on the solid wall corresponded quantitatively well with experimental results especially for high Reynolds numbers. The effect of the surface tension on the film profile was almost negligible for the simulated range.

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A three-dimensional rectangular wing is set up in the low Re flow field. The fluid is assumed to be incompressible and viscous. The Navier-Stokes equations are solved by the numerical computation. The computational result is compared with the experimental data. The characteristics of the flow field is analyzed.

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A fluid-structure coupling approach based on level set function is proposed in order to solve large deformation problems that are difficult to interface tracking method, such as ALE (Arbitrary Lagrangian-Eulerian) method. The fluid flow field is solved by using fixed mesh because the level set function can describe a complicated geometrical shape in analysis grids easily. In this study, kinematrical condition treatment with virtual particles is introduced at the fluid-structure interface and iterative computation based on a partitoned solution method is implemented.

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The paper discusses several aspects of the construction of approaches that combine statistical (RANS) models with large eddy simulation, with the objective of making LES an economically viable method for predicting complex, high-Reynolds-number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail - one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

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Recently, the high speed limit and high performance of cars have been advanced. Then it is necessary to adapt them to environmental problems and improve passengers' comfort. Therefore, the aerodynamic characteristics have more importance. Car companies have devised the shapes of bodies and parts, and reduced the drag and lift. The purpose of the present research is the investigation of the effects of the spats and strakes on the aerodynamic characteristics. A wind tunnel with a moving belt was used to measure the drag and lift. As a result, the drag is decreased when the spats are attached on the wheelhouses, but is not very much when the strakes are attached on the underfloor.

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Relationship between drag reduction and microbubble motion in a vertical Taylor-Couette flow is investigated by visualization of r-z cross section. We have measured the vorticity distribution in two-phase condition by means of particle tracking velocimetry (PTV). The bubble distribution shows two modes as Re number changes, i.e. toroidal and spiral modes. In low Re number region, the vortex structure is modified significantly by the bubbles. The presence of bubbles provides elongation of vortical wavelength to be around 1.5 times as that without bubbles. This alternation of the cell yields a large reduction ratio of the shear stress in low Re number region while the drag reduction effect is weakened as Re number increases for the high kinetic energy of the cell motion.

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Reduction of the noise along a high-speed railway line is very important for further speed-up of a high-speed train. We have developed the technique of aerodynamic noise reduction by porous material and are trying to apply this technique to an actual pantograph. However the details of the mechanism of aerodynamic noise reduction was not clear. To clarify that mechanism, aerodynamic noise, aerodynamic force and flow field around a test cylinder with or without porous materials (porous urethane, porous metal, fur material) was measured by the wind tunnel test. In this report, experimental results of the wind tunnel test about aerodynamic noise and aerodynamic force are shown.

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Aerodynamic noise from bluff bodies is well reduced when they are covered with porous materials. To clarify this mechanism we measured wake velocities behind a cylinder covered with porous material by the particle image velocimetry (PIV) technique and characteristics of sound absorption of porous material by using pressure transducers and a loud speaker. Vortices shed alternately from the cylinder disappear and a region of zero-velocities is spread widely behind the cylinder. Shear layers between the stationary region and the uniform flow are thin and stable. Porous material does not absorb sound wave. These results suggest that porous material affects mainly the flow field around the bluff bodies and reduces aerodynamic noise by depriving momentum of the wake and suppressing unsteady motion of vortices.

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Turbulent drag reduction and heat transfer were investigated in surfactant solutions for a small-scale pipeline system composed complex elements. The effects of the counter-ion concentration were discussed on the drag reduction, the viscoelastic characteristics, and the vortex inhibition. When the molar concentration of the counter-ion was thirty times higher than that of the surfactant, the solution produced the drag reduction, and the increase in viscosity and the degradation of heat transfer did not appear. All surfactant solutions including this concentration combination of counter-ion and surfactant exhibited the vortex inhibition at a higher stretching rate.

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Surfactant additives have been attractive as practical drag-reducing additives because they were not affected by the degradation due to mechanical shear action and they could apply to the circulatory system. There are only a few studies on drag-reducing effect of nonionic surfactant solutions, although a lot of studies for cationic surfactant solutions have been performed so far. The influence of drag-reducing nonionic surfactant solution at 4000 ppm and 6000 ppm on the pipe flow and turbulent boundary layer was investigated.

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It has been reported that malted rice solutions cause the drag reduction phenomena in turbulent flow range. The drag reduction is classified in the Type-B for the friction factor of a circular pipe flow because of biopolymer solutions. Although it is an important problem to be solved saving energy for the hydraulic transportation of a pipeline system awaiting solution, some problem lays in the practical application for it. In this paper, we clarified the effect of the culture condition on the drag reduction phenomena by using a pipe friction measurement system.

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Direct numerical simulation of a zero-pressure gradient drag-reducing turbulent boundary layer of viscoelastic fluids was performed at the momentum-thickness Reynolds number Re_θ_0=500 and Weissenberg number We=25 using constitutive equation models such as the Oldroyd-B, Giesekus (the mobility factor α=0.01, 0.001, 0.0001) and FENE-P models (the extensibility parameter L^2=100, 1000, 10000). It was found that the maximum drag reduction ratio DR(= 45%) for the Giesekus model with α=0.0001 was the largest. In the case of the same elongational viscosity, the drag reduction ratio for the Giesekus model is larger than that for the FENE-P model.

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The pressure losses for four kinds of PTFE(Poly-Tetra-Fluoro-Ethylene) pile surfaces and a hybrid riblet surface were measured in a rectangular water channel flow using the water and a glycerol-water mixture. The data were compared with those of smooth surfaces. The drag reduction could be obtained for all kinds of PTFE pile surfaces and the hybrid riblet surface; the maximum reduction ratio was estimated to be 6% for PTFE1 (the shorter and the finest fiber) and PTFE4 (the shorter and the thickest fiber). The maximum reduction ratio obtained for the hybrid riblet surface was 7%. It was found that for PTFE pile surfaces, a drag increase due to the effect of surface roughness appeared when the Reynolds number exceeds about 8000. The photograph of x-y and y-z cross-sections of PTFE pile surfaces taken by using a microscope revealed that there was somewhat space between the base fabric and pile fibers. For the hybrid riblet surface, drag-reducing effects due to both the larger and the smaller ribs were observed.

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We study the effect of hydrophobic surfaces on drag reduction in Newtonian laminar flow through a rectangular channel. Fine fabrication is given to the test wall surfaces so that the groove pattern and the groove area ratio may be changed methodically, and their surfaces are coated with PTFE. Hereby the surface shows the high contact angle as 135°. Drag reduction is estimated by pressure loss measurement in a 12 x 12 mm channel. A series of experiments shows that the drag reduction increases with increase of the area ratio of the groove when the aspect ratio is large enough. The drag reduction ratio is obtained to 5%. Furthermore it is indicated that the difference in the groove patterns gives the difference to the drag reduction. Air-liquid interface is visualized in relation to the drag reduction, and the interface shape is observed.

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Direct numerical simulation on turbulent channel flow with blade riblets was performed using the immersed boundary method. The drag-reducing effect of multi pitch riblets were investigated. It was found that the drag reduction ratio of about 10% was obtained in single pitch riblet and a certain multi pitch, but the other multi pitch riblet weaken the drag-reducing effect.

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The nonlinear bifurcation analysis is employed to investigate the effect of the system rotation to the fluid flow in a vertical slot laterally heated. Secondary and tertiary solutions are annihilated by the rotation oriented in the streamwise direction. Moreover, we found a quasi 2-dimensional solution, which supercritically connects the tertiary solutions.

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