As a part of study on the diffusion control of jet flow, the purpose of this study is to control the jet diffusion using the deforming nozzle. The shape of polypropylene nozzle can change from square shape into cruciform one smoothly. The velocity measurement of the jet flow was carried out by using a hot-wire anemometer, by changing the shape of nozzle variously. The basic characteristics of the jet, such as velocity distributions, half value widths and turbulent intensities were obtained. As a result, it has been found that the jet width in xOy'-plane is large, comparing with that in xOz-plane. Moreover it has been also clarified that the effect of the deforming of the nozzle on jet diffusion is appeared in xOy'-plane.

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In order to develop a new heat transfer procedure of impinging jet, we conduct a DNS (direct numerical simulation) of controlled impinging jet. As a proposed procedure, a nozzle is rotated around a given axis normal to the impinging wall. Prom view of instantaneous velocity magnitude and instantaneous vortex structures, it is found that jet circumferentially rotates depend on the rotating frequency in the free jet region, and that the jet diffuses largely compared to the case of the uncontrolled jet. In order to estimate the heat transfer performance, the local Nusselt number distribution is calculated. For the controlled case, the heat transfer performance around the impinging position markedly decreases compared to the uncontrolled case, however it is found that a homogeneous heat transfer appears around the impinging position under a specific frequency of rotation and a rotating radius.

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Active control of the diffusion of a circular jet was attempted by application of a secondary film flow around the jet. Sinusoidal acoustic excitation of the film flow was carried out for VR values 0.5, where VR is the ratio of the film flow velocity to the main jet velocity. For VR = 0.5, the diffusion of the jet was suppressed compared to that of a single jet but it was somewhat enhanced by the acoustic excitation. The acoustic excitation shortened the potential core of the jet; however, the entrainment of the ambient flow was far less than in the case of a single jet, regardless of degree of excitation. We conclude that secondary film flow can control diffusion and that acoustic excitation can enhance the diffusion of jet flows. It is worth investigating this mechanism in detail in future studies.

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The validity of dielectric-barrier-discharge plasma actuators as spread controller of turbulent free jet issuing from rectangular exit was investigated. Rectangle nozzle of 75mm×10mm (Aspect ratio 7.5) was used and two plasma actuators were placed at the long side of the nozzle exit. The jet velocity at the nozzle was set at 5 m/s and the velocity in the downstream section was measured by a hot wire probe. When actuators were operated with the condition that Duty was 10% and the modulation frequency was 1/8 of the characteristic one and in opposite phase, the jet spread remarkably in xy-plane. On the other hand, when Duty was 30% and modulation frequency was 700 Hz, vortex appeared at closer position to the nozzle exit and it broke down in a short while without growing up, and the spread of the jet in xy-plane was delayed.

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Impinging jets are one of the most industrially essential techniques for cooling the gas turbine blades and electronic devices, drying glasses, anneal and so on. Usually, multiple jets are arranged for appropriate cooling, but they make complicated flow by interaction with each other at near the impingement surface. In the present study, complicated three-dimensional flow configuration of square arrayed circular impinging jets was revealed experimentally for referring to the effect on heat transfer performance. The flow field was measured by scanning stereoscopic particle image velocimetry to confirm the detailed spatial features of the jet interaction as changing nozzle-to-surface distance and jet-to-jet spacing. In this occasion, it is confirmed that the adjacent jets configure the distorted rings which surrounds jets. The large upward roll-up that is also indicated.

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The effects of uneven flow on the surface pressure coefficient in a finite row of four circular cylinders have been investigated by using the visualization of smoke-wire method and by measuring the surface pressure distribution. The experiments are carried out by the wind tunnel testing at a blockage ratio of 13.3% and the Reynolds number of 6000. The cylinder spacing ratio, defined as the ratio of the adjoining cylinders center-to-center spacing distance against the cylinder diameter, is kept 1.25. As the results, the visualization of the smoke-wire method displayed there were five patterns of the uneven flow, and the uneven flow patterns were divided into two groups. The surface pressure distribution exhibited the different result dependent on the uneven flow patterns.

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The purpose of this study is to understand the details of the vortex roll-up process in the wake of the flat plate. Instability analysis is well known, but the details of physical mechanism of vortex roll-up are not understood enough. Flow patterns in the wake of the each flat plate with different thickness of trailing-edge were observed in detail by various flow visualization techniques, and the ralations between flow pattern and vortex roll-up process were showed.

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The vortex shedding behind a circular cylinder is one of the important issues in engineering mechanics, because the vibration induced by the vortex shedding, can cause a serious accident. In order to suppress it, the present study aims to control the vortex shedding from the cylinder. In this paper, the spherical rings were attached on the cylinder, and the streamwise and transverse velocities in the cylinder wake and the static pressure on the surface of the cylinder were measured by the hot-wire anemometer and the pressure transducer at Re_d ≈ 15,000. Also, to investigate the flow structure in the wake, the phase-averaged velocity was calculated by the conditional sampling method. As a result, it was found that the flow behavior is affected by the spanwise pitch of the spherical rings.

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This study presents a Vortex in Cell (VIC) method for incompressible flow around solid bodies. It is in conjunction with an Immersed Boundary (IB) method using a penalization term to satisfy the non-slip condition on the body surface. The presented method is applied to the two-dimensional simulation of the flow around a circular cylinder. The Reynolds number ranges from 100 to 1000. The Karman vortices are successfully simulated. The Strouhal number and the drag coefficient of the cylinder are favorably compared with the corresponding experimental results, demonstrating the validity of the simulation method.

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In this study, intermittent control of the coaxial type DBD plasma actuator which generates an induction flow in a jet and the direction of the coaxial is performed. We performed simulate for research to diffuse gaseous mixture of fuel and air, it is that we attempted to intermittent control by plasma actuator using the carbon dioxide with the same molecular weight as propane. When duty was controlled by synthesizer, the influence on the main jet was investigated. As a result, two changes were seen by comparing the intermittent control on and off. One is that the potential area of the jet collapsed as a whole. Another is that the center velocity of the jet flow is decelerated by the Nozzle wall velocity is accelerated.

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Jet flow, issued into a density-stratified fluid in a tank, and the resultant mixing phenomena are simulated. The velocity and concentration fields were experimentally investigated by the authors' previous study. The upper and lower fluids are water and NaCl-water solution respectively, and the lower fluid is issued vertically upward from a nozzle at the bottom of the tank. The simulation highlights that the jet behavior depends on the Reynolds number and that it agrees well with the experimental result. The simulation also demonstrates that the mixing between two fluids, promoted with the vortical flow induced by the jet, is successfully grasped.

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The effect of periodic disturbances introduced with oscillating plates has been investigated on a jet issuing from a rectangular nozzle. The oscillating plate consists of a laminated piezoelectric element and stainless plate. The experiment was performed at the outlet velocity of U_0=5(m/s). The cross sectional area of the rectangular nozzle has a size of 10mm×10mm. Velocity components were measured with single hot-wire probe and CTA. Oscillating frequency was set at 1/4, 1/3, 1/2 and 1 times of a natural occurrence frequency. From the streamwise variation of turbulent intensity on the jet centerline, disturbance was classified into three non-dimensional oscillating frequency of 0, 1/2 and 1/3. In an early stage of the jet, stable large-scale vortical structures were observed at the non-dimensional oscillating frequency of 1/2 and 1/3. The decay of the streamwise mean velocity on the centerline and growth rate of the half width increase at the non-dimensional oscillating frequency of 1/2.

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It is known that the cloud cavitation shows periodic unsteady behavior but there remain some points to be solved on the cavitation instability. In order to make clear a mechanism of cavitation instability on the role of the nozzle divergent part, we experimentally examined the cloud cavitation using a high speed video camera and an image analysis based on the frame difference method to quantitatively estimate the unsteady cloud behavior. As a result, we found that the generation mechanism of reentrant motion is dependent on the difference in the upstream pressure of nozzle as well as the shape of nozzle divergent part. In addition we indicated that for nozzles with a divergent part the pressure wave issued at cloud collapse may hardly affect the reentrant behavior of cloud cavitation.

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This study was focused on vortex structures in a forced rectangular jet. The periodic and alternative disturbance locally excited a pair of major shear layers. The flow visualization was performed by Laser Induced Fluorescence method to grasp 3-D image by stacking the time sequence of cross section images. As a result, the detail of tilting-link structure was observed, and it was revealed that the structure forms only in the excited jet. Mushroom shaped vortex enhances mixing and diffusion in the minor direction of the jet. On the other hand, the jet contraction in major direction is due to the self-induced velocity of the rectangular vortex ring.

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An electro-conjugate fluid is a new type of functional fluid, which can exhibit functional properties in an applied electric field. The application of a high voltage to a pair of electrodes immersed in a certain dielectric fluid induces the occurrence of a strong micro-jet between the positive and negative electrodes. These fluids are called the electro-conjugate fluid, and the phenomenon of the occurrence of the micro-jet is called the ECF effect. We have performed a flow visualization experiment with the 2D PIV analysis. For the case of the cylinder-cylinder electrodes, the maximum velocity of the micro-jet arises on the line connected between the centers of the positive and negative electrodes. A micro-jet occurs at the position of the maximum gradient of the electric field at the surface of the positive electrode and flows toward the largest gradient position of the negative electrode.

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Dragonfly perform very advanced flight. It is caused by the difference in partial stiffness of the wing elasiticity. Therefore, we pay attention to the partial stiffness of the dragonfly's wing. Numerical simulation based on the finite difference method is employed to investigate the influence of the wing elasiticity. The theory is suggested by the elasiticity of the cylinder as the equivalent of the real elasiticity of the dragonfly's wing. However, it is undestood that the elasiticity by a suggested theory was different from the real elasiticity of the dragonfly's wing. So, we performed a elasiticity measurement by the new measurement method to investigate the real elasiticity of the wing.

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Under-water glider is the glider to use for environmental researches in sea and lake. Reynolds number of flow around under-water glider is low such as between 1×10^4 and 1×10^5. Performance of wing at low Reynolds number is different from that of high Reynolds number. In this study, aerodynamic characteristics of three dimensional wings with various airfoils which have sinusoidal leading edge at low Reynolds number were investigated by the wind tunnel experiment and compared with that of normal shape. It was found that sinusoidal leading edge a=0.05c increase lift coefficient at high angle of attack and maximum lift-to-drag ratio independent of the airfoil. It was also found that decreases in drag coefficient were observed in symmetric airfoil NACA0012 and thick airfoil NACA64_3-618 with sinusoidal leading edge.

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We dealt with the wake of a permeable disk with different solidity as a simple model to investigate an essence of wake of a wind turbine. Velocity defect at the center of the streamwise cross section of the wake was measured at each downstream position by hot-wire anemometer to characterize the wake. Variations of the velocity defect obey power law in far wake regions and the variation of the corresponding index numbers with respect to the solidity has the local maximum. It suggests there is a regime change on the vortex structure. We also investigated the wake of a model of two-blade turbine. Here the variations of the velocity defect show different tendency in far wake regions.

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A new type wave power generation system is proposed to be installed in a vertical slit type breakwater. The merits of the system are listed as follows, (i) no occupation of the sea surface, (ii) maintenance facility, and (iii) high energy efficiency by using accelerated flow from the slit of breakwater. In this study, several kinds of water wheels were examined to be installed in a model wave breaker with 1/12 scale ratio to the actual system. The experimental results show that the crossflow type has a higher performance. Ina addition, a bending plate type generator was examined to achieve higher efficiency. When the elastic plate is bent by the drag of wave, a tension appears and a wheel and axle is rotated. The performance of bending plate generator is examined under various experimental conditions. The output per occupied sea area is expected as 23,500(W/m^2) in the real system.

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Some important points remain unsolved though it is considered that the instability can be divided into two categories such as a mechanism peculiar to cavitation and the other caused by system factors such as surge. The mechanism of cavitation instability is summarized and explained using several results of the authors' group. In the present study a high speed water jet with cavitation is mainly investigated as a typical cloud cavitation phenomenon. Especially an image analysis method based on frame difference from high speed video observation is applied for three kinds of cavitating nozzle flows to catch the motion of pressure waves which is one of the key factors to solve the reentrant motion mechanism. As a result, the cavitation instability mechanism can be explained with the use of the present image analysis method.

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This study has been conducted to investigate the development of large-scale turbulent structures behind a backward-facing step. Two-dimensional velocity field was measured by a flying hot-wire technique with X-type multiple probe rake, and distributions of the mean and fluctuating velocity, Reynolds shear stress and forward flow fraction were obtained over x/H = 0.15 to 10. Proper orthogonal decomposition was employed to analyze the large scale structures in the separated shear layer. POD coefficients of the u- and v-component at the first mode were found to have a negative correlation with each other, and flow structures reconstructed with this POD mode contribute largely to the generation of the Reynolds shear stress.

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Moving body produces the dynamic lift from the vortex rings over the body and in wake field. However, it is not clarified how long we should evaluate the vortex ring in wake filed when we estimate the dynamic lift. The purpose of the present study is to examine evaluation method of the vortex ring in wake filed to estimate the dynamic lift produced by butterfly. Therefore, it is clarified that the influence of the vortex ring emitted in wake field during before prior motion on the dynamic lift is small. Consequently, it is possible to estimate the dynamic lift using vortex ring emitted in wake filed during prior motion.

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PIV measurement needs tracer. Generally, solid particle is used as tracer. Solid tracer, however, tends to accumulate on the gap located at wall. It might cause the machine trouble if actual machine was used for the measurement. In this study microbubble is proposed as PIV tracer. In order to investigate whether microbubble is effective as tracer, loci of both microbubble and solid particle tracers are calculated and then compared. Results show both loci are coincides each other. Next, mean velocity distribution of turbulent flow over a backward-facing step is measured by PIV using microbubble and solid particle as tracer. Results show both distribution are well coincide. It can be said that microbubble is available as tracer for PIV measurement of time averaged velocity field.

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The aerodynamic characteristics of 0.4m span 65°delta wing are investigated in low Reynolds number flow. Lift and drag coefficients are obtained by using six component force load cells in a low speed wind tunnel. The effects of tapered leading edge flaps are considered by PIV measurements accompanied with the force data.

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PIV measurement using microbubbles as tracers was attempted. Mean diameter of employed microbubble is around 65μm. 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=3700,5500) 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. On the other hand Reynolds stress at Re=5500 distributes lower than that obtained by others.

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High speed airflow is generated around a rotational grinding wheel in the cylindrical grinding. Coolant is supplied to prevent from grinding bum, but it cannot reach to the grinding point because of the high speed airflow. This paper describes the flow characteristics around a rotating disk (rotational grinding wheel). The effects of an air scraper and a thickness of rotating disk on the development of airflow around a rotating disk were investigated by the flow measurement by using laser-Doppler velocimetry and the numerical simulation by using the commercial software ANSYS FLUENT. The tangential velocity profiles around a rotating disk without a scraper have a similarity. The scraper can be suppressed the high speed airflow around a rotating disk. It is found that the airflows from both sides surface of rotating disk have a great influence on the development of airflow on the periphery of rotating disk.

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We experimentally investigate the vortex breakdown (VB) of swirling jet with density difference in inverted gravity (+1g). The trends of the changes in the jet half-angle and stagnation point height are investigated in detail for the stable VB. Our physical model derived by considering the momentum balance in a swirling flow is adopted to understand the mechanism of the change in the stagnation point height in +1g with increasing swirl number of the inner jet and Reynolds number of the outer jet.

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We attempted to determine the number of frequency components required for efficient turbulence generation. A random-phase mode was applied for generation of turbulence where an input signal was fed to each fan with quasi-random phases. We used an input signal composed of two frequencies by this method and investigated characteristics of the turbulence. The turbulence far enough downstream generated by two-frequency mode has almost the same characteristics as that by the forty-frequency mode, but the development of power spectrum is much slower for the two-frequency mode than for the forty-frequency mode.

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The objective of this study is to understand the influence of body impinging to the water surface. Our question is how will the fluid be moved with the body impinging. The spherical body used in the experiment. The flow was visualized with two methods. One is the visualized with digital camera to observe the path line by using long exposure technique. The other is using high speed CMOS camera. The combining of these techniques has two advantages. One is high spatial resolution, and the other is high time resolution. The results show that the path line indicates two phases of flow formed by impingement of body. One, the fluid moved with the body entering the water by a hill's vortex like flow. Two, the fluid moved with deformation of water surface by formation of water splash. The potential like flow formed with the flow impulsively accelerated by the body impingement.

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Abrasive water jet cutting has been used in the field of rough cutting and need machining. Because 1.0-1.5mm of cutting width and accuracy of cutting path are not suited to micromachining. Now, we develop abrasive head for small diameter nozzle, abrasive feeder, cutting machine and other technology for micromachining by abrasive water jet. In this paper, we show these technology and cutting example.

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Abrasive water jet which is 3-phase flow consisting of water, air and abrasive particles is more destructive than pure water jet consisting of water and air. So it is applied to the field of mechanical processing, construction and so cm. As new application field, food processing is considered. In food processing, garnet that is general material as abrasive is not able to use because of insanitary and unfit to eat. Salt has possibility as abrasive particles but it may melt the moment it touches water. This study is a research of the possibility of salt as abrasive.

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An abrasive injection jet (AIJ) has a tendency to pulsate violently as abrasive flow rate increases. One of main sources of the pulsation is considered to be fluctuation of the abrasive supply to the nozzle head. High-speed observations of the flow in an abrasive supply tube are conducted in the present investigation. For simplicity, a straight abrasive supply tube is connected horizontally to a suction chamber. Abrasive particles tend to form clusters while particles are transferred in the tube.

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A ventilated sheathed nozzle for producing abrasive suspension jets (ASJs) has been developed as a means of extending the effective standoff distance and improving the cutting capabilities under submerged conditions. In the present investigation, submerged cutting tests were conducted with aluminum specimens at a jetting pressure of 30 MPa to clarify the effects of sheath length and air flow rate on the cutting capability of ASJs. Under the present experimental conditions, a nozzle with shorter sheath is preferable for submerged ASJ cutting. High-speed observations show that the air filled cavity downstream of the sheath exit is very unsteady and tends to be pinched off periodically, namely pulsates. A compact ASJ can be made by using a longer nozzle mount.

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Water jets issuing from a fan jet nozzle (fan jets) are used in radiological decontamination, coating removal, and cleaning. However, the flow characteristics of fan jet have not been clarified sufficiently. An experimental study is conducted to clarify the flow structures and the velocity fields of fan jet and abrasive suspension fan jet issuing from a fan jet nozzle. The velocity fields of the fan jets and the abrasive fan jets are calculated using PIV (Particle image velocimetry). It is found that the time average velocity field of the abrasive fen jet is lower than that of the fan jet.

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This paper presents an experimental study on the liquid droplet impingent erosion of aluminum material using the high-speed spray jet. The flow configuration studied is the pin-hole type erosion, which has the erosion depth comparatively larger than the spray width. The experimental result shows that the growth rate of the erosion is decreased with an increase in the erosion depth due to the influence of liquid film and their relationship is formulated.

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Liquid has very large surface area when it becomes a lot of tiny drops. Atomization using water jet is a process that makes a lot of drops at once. We propose a separation method of mixed liquid by water jet. It has advantages that atomization using water jet does not require so much energy and thermal denaturation does not occur. In this study, the performance characteristics on separation of mixed liquid by atomization using water jet is investigated. As the results, the relation between separation characteristics and environment temperature is obtained.

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In order to enhance aggressive intensity of a cavitating jet in water, nozzle throat length L_t was optimized in a nozzle with cavitator. The aggressive intensity of the jet was evaluated by erosion test in aluminum plate specimens. The obtained results show that L_t = 5 mm is optimum nozzle throat length. Mass loss at optimum standoff distance of L_t = 5 mm nozzle is 20 % larger than that of L_t = 6 mm conventional nozzle.

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We focus on cavitation erosion in submerged cavitating water jet, especially around jet center part. The appearance of cavitation cloud was examined using a high-speed video camera from two directions, such as side-view and back-view of impinging wall. The high speed video images are estimated by an image analysis based on the frame difference method. The cavitation impacts were measured at the jet center area on the impinging surface together with the cloud appearance. As the result, we found that the erosion of jet center area is caused by the collapse of the existing cloud on the impinging wall.

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Machined parts has many chips and burr in or on itself. If machine parts are assembled with these, assembled unit will be operation failure. When the unit is very important unit in automobile like ABS, it has risk of life. Washing of machine parts is very important. Submerged water jet washing machines has been used in field of these machine parts washing. This paper shows latest submerged water jet washing machine.

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In this study, the effect of 3-dimensional blade on the turbine characteristics of Wells turbine for wave energy conversion has been investigated experimentally by model testing under steady flow conditions, in order to improve the stall characteristics and the peak efficiency. The aim of 3-dimensional blade is to prevent flow separation on the suction surface near tip. The chord length is constant with radius and the blade profile changes gradually from mean radius to tip. The blade profiles are NACA0015 from hub to mean radius and NACA0025 at tip in this study. The performances of Wells turbine with 3-dimensional blades has been compared with those of original Wells turbine, i.e., the turbine with 2-dimensional blades. As a result, it was concluded that the peak efficiency of Wells turbine can be improved by the use of the proposed 3-dimensional blade.

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A twin unidirectional impulse turbine has been proposed in order to enhance the efficiency of wave energy plant. This turbine uses two impulse turbines for unidirectional airflow and their flow direction is opposite each other. The turbine characteristics under steady flow conditions were investigated numerically by computational fluid dynamics (CFD) and compared with the experimental results. The effect of rotor blade profile on the performances were discussed in this study. Then, a suitable blade profile for the twin turbine was proposed.

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Wells turbine has inherent disadvantages in comparison with conventional turbines: relative low efficiency at high flow coefficient and poor starting characteristics. To solve these problems, the authors proposed Wells turbine with booster turbine for wave energy conversion. This turbine consists of three parts: a large Wells turbine, a small impulse turbine with fixed guide vanes for bi-directional airflow, and a generator. It was conjectured that, by coupling the two axial flow turbines together, pneumatic energy from oscillating airflow is captured by Wells turbine at low flow coefficient and the impulse turbine gets the energy at high flow coefficient. The performance of turbines under steady flow conditions has been investigated experimentally by model testing. Furthermore, we estimated mean efficiency of the proposed turbine under oscillating flow conditions by quasi-steady analysis, in order to investigate the effect booster diameter on the mean efficiency.

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A straight-bladed vertical axis turbine for wave energy conversion has been proposed in order to develop a novel air turbine suitable for OWC based on wave energy plant. The objective of this study is to clarify the effect of guide vane on the performance and the starting characteristics of the straight-bladed vertical axis turbine. Performances of the proposed turbine under steady flow conditions have been investigated experimentally by using a wind tunnel. The tested rotor has some straight blades with a profile of NACA0018, a pitch diameter of 460 mm and a width of 490 mm. Starting characteristics of the proposed turbine have been simulated by using quasi-steady analysis.

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A wave power generator with an impulse turbine is installed in the breakwater and consists of the air-chamber, the turbine, the generator and the safety devices. The purposes of this paper are to construct the design method. As for the motion of water inside the air-chamber, that is, the oscillating water column (OWC) is solved by the eigenfunction expansion method. The characteristics of turbine and OWC for irregular wave are solved by assuming the Gaussian distribution for the probability density of the flow rate of turbine. The output limit is considered by the simple assumption for the turbine and generator. An initial design decides the turbine size, the rotational speed and the rated generator power from calculation results for the several wave conditions.

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Wave energy is one of the most hopeful renewable energies. A floating point-absorber with an oscillating body type conversion system will be lower cost and suitable for the offshore powerful wave energy. Although a resonant control strategy is suitable for the oscillating body type converter, it is practically difficult to use because of the mechanical and electrical system limitations. It is important to design an optimal control strategy in the limitations. In this study, a new concept with detuned parameters for a resonant control system is discussed by using a time-domain numerical simulation of the converter. It is presented that the maximum displacement of the converter is reduced by the detuned parameters for the resonant control.

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Darrieus-type hydro-turbine system has been developed for low head hydroelectric power generation. When Darrieus-type hydro-turbine with/without two-dimensional symmetric inlet nozzle is operated in open channel flows like river and agricultural water way, generated power is known to be increased by installing inlet nozzle. In this research, the effects of converging angle and nozzle outlet width on turbine performances are investigated in order to find the ideal shape of inlet nozzle. As a result, the turbine with the inlet nozzles having converging angle of 45 and 60 degrees can generate larger power than that with 30 degrees under the constant nozzle outlet width. The turbine with the inlet nozzle whose outlet width is 0.9 times diameter of runner pitch circle produces larger power than those with the narrower nozzle outlet widths.

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The final purpose of this study is to develop a water turbine appropriate for low-head open channels in order to effectively utilize the unused hydropower energy. The application of the cross-flow runner to open channels as an undershot water turbine has come under consideration. However, the flow field of undershot cross-flow water turbines possesses free surfaces. This means that with the variation in the rotational speed, the water depth around the runner will change and flow field itself is significantly altered. Thus it is necessary to clearly understand the flow fields with free surfaces in order to improve the performance of this turbine. In this study, the performance of this turbine and the flow field were studied through experiments and numerical analysis. The particle image velocimetry (PIV) technique was used for flow measurement. The experimental results on the performance of this turbine and the flow field were consistent with the numerical analysis.

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A hydraulic turbine for an open channel can generate power at low head and doesn't affect the environment because it doesn't have incidental equipment. However, because the rotational speed is low, the hydraulic turbine outer diameter becomes large. Therefore, we proposed an axial flow hydraulic turbine with collection device, using kinetic energy of open channel flow. The analysis performances and flow fields of runner only, collection device only and combination of runner and collection device were clarified. However, open channel flow has a free surface, so it is not sufficient for the analysis so far assuming uniform flow into the hydraulic turbine, which is installed in a wide space. In this study, for the purpose of evaluating the quantitative performance characteristics of this hydraulic turbine, we conducted performance tests and PIV measurements of the flow field around the hydraulic turbine.

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Small hydropower generation is one of important alternative energy, and potential of small hydropower is great. Efficiency of small hydro turbines is lower than that of large one, and these small hydro turbine's common problems are out of operation by foreign materials. Then, there are demands for small hydro turbines to keep high performance and wide flow passage. Therefore, we adopted contra-rotating rotors which can be expected to achieve high performance and low-solidity rotors with wide flow passage in order to accomplish high performance and stable operation. Spokes needs to support rotors, and influence on the performance of the small hydro turbine. The performance of the contra-rotating small hydro turbine is investigated when the spokes shapes are changed. The test small hydro turbine is improved by the spoke shape modification, and the internal flow of it is clarified by the numerical analysis results

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Forward Osmosis (FO) is expected to the new water treatment in sea water desalination system and salinity gradient energy power generation technique. The performance of the FO module is closely relating to water flow and permeation characteristics. In this paper, the permeation performance of the fresh water is studied for the hollow fiber membranes in relating to the diameter of it. It is pointed out that the permeated flux of the fresh water of the membrane module is proportional to 0.5 power of diameter of the hollow fiber. Therefore, the optimal diameter exists to the maximum flux of the permeation.

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