In various manufacturing process, particle contamination is one of the critical problems. A wet cleaning is widely used, but it is difficult to evaluate the cleaning performance. In this study, first we have tried to make high adhesion force samples which can evaluate particle removal rate of wet cleaning like PVA brush scrubbing or droplets impacts. Second, we measured its removal force directly by using self-sensitive cantilever. We have already measured the removal force in the air. We tried to measure also in the water in this study. As a result, the peeling forces in both air and water were about 10² μN. We estimated that this is because the influences of humidity like liquid bridge force are very small compared with adhesion force. Finally, using this sample, we demonstrated the cleaning performance of PVA brush scrubbing. We could quantitatively evaluate wet cleaning by using particle removal rate.

Ultrasonic Velocity Profiler; UVP method is applied to various fluid flows including the multiphase flow. Most UVP measurements were carried out using the commercial measurement devices. However, a flexibility of measurements is restricted due to that fact. This article discusses development of UVP measurement system. The system consists of a pulser/receiver, an ultrasonic transducer, an analog-to-digital converter and a PC. Selection guide of hardware is provided. Velocity estimation is performed with full-digital signal processing, which eliminates complicated adjustment of analog circuits as it used to be. Typical signal processing principle and its efficient implementation are discussed. Bubbly flow measurement using this system is presented as an example of application.

Taylor-Couette vortex flow with a low-aspect-ratio has characteristics such as the different vortex structure, because of a boundary layer of the top and bottom wall and the acceleration of the inner cylinder. In a case of large aspect ratio of Taylor Couette flow, the mechanism of the vortex like a chaotic flow has been shown by Fenstermacher and Takeda. The purpose of this study is to understand the flow mechanism with Taylor Couette system of the low-aspect-ratio using an ultrasound measurement and a numerical simulation. In this report, we mainly analyzed the process of transition to turbulent flow by using a spectra analysis in a radial and an axial direction.

In this study, measurements of droplet size and velocity in vertical upward annular-mist flow flowing up a vertical pipe with 10 mm-ID were performed using an image-processing based on a shadowgraph technique. Transient characteristics of droplet flux and velocity were also evaluated by means of the present technique. Total 9 datasets were obtained at the predetermined superficial liquid and gas velocities, ranging from 20 to 40 m/s for gas phase and from 0.1 to 0.4 m/s for liquid phase. The measured droplet size distribution varied greatly with change in gas flow rate, while its weak dependence on liquid flow rate at the fixed gas flow rate was confirmed. The measured droplet velocity profiles in pipe cross-section tended to obey the one-seventh-power law. Insignificant local slip velocity between gas phase and droplets was confirmed, while its average value tended to slightly increase with droplet size.

Experimental evaluation of surfactant concentration at a fluid-fluid interface is in great demand for understanding adsorption-desorption kinetics at the interface. In this study, spatiotemporal filter velocimetry (SFV) is applied to flow about a single drop of glycerol-water solution falling in a stagnant silicon oil under a contaminated condition. Distributions of surface tension and surfactant concentration along a longitude line of the interface are evaluated from the velocity distributions measured in the vicinity of the interface. The budget of the surfactant concentration is also evaluated from the measured data. The result shows that the evaluation of surfactant concentration using SFV is of great use in understanding adsorption-desorption kinetics at an interface in a contaminated system and for validation of numerical methods taking into account adsorption and desorption of surfactants.

This paper presents the test results for checking the performance of digital holographic particle measurement with high spatial resolution by numerical simulation. In this technique, a governing equation, the Fresnel diffraction formula, is numerically solved with the simplest discretization technique to easily adjust the spatial resolution of reconstructed images by a parameter of pixel size on image plane. Performance tests are carried out for four different particle diameters by changing the magnification parameter depending on the pixel size. It is shown from the test results that the RMS error in diameter is saturated at 0.5-0.8 μm that is smaller than one pixel size on a digital hologram, 3.45μm, for any size of particle diameters 10-30μm.

In this study, the electrical generator is developed to generate electricity in the Tsugaru Strait. However, the Tsugaru Strait has little quantity of generation because speed is slow. Because so I applied a wind lens technology and intended to let you rise speed. We devised Brimmed diffuser for tidal generation with integrated water turbine and power generation section supported by circumference. The purpose of this study is to find out whether Examination of the circumference support method of the lens waterwheel for tide generation. Therefore I thought that It is an axis cost cut, a seal-free, and there is no tip clearance.

In order to obtain the high output at the periodical bi-directional flow similar to tidal flow, the experimental research for tidal energy conversion system with impulse turbine was carried out. The unique tidal energy converter having the collector to increase the input and output power was adopted. Its outline shape was selected from the result of previous research. To improve the output power of tidal energy converter, three kinds of turbine rotors with different hub-to-tip size, i.e. 0.7, 0.6 and 0.5, were tested. As a result, the effect of hub-to-tip ratio of turbine rotor on tidal energy conversion system was clarified in this research.

The environmental problem and related energy problem are recently the serious problem all over the world. The renewable energy is now highlighted as one of the solution to the problem. The possible use of ocean current as an energy resource begins to draw attention in the renewable energy. In this paper, horizontal axis ocean current turbine performance estimated by Computational Fluid Dynamics is carried out. The numerical estimation method is able to calculate not only a turbine performance characteristics but also turbine with shroud (the collection device) performance characteristics. This method is validated by comparing with experimental results.

An OWC type wave power generation is consisted of an air-chamber with an oscillating water column (OWC) and a turbine-generator. Two numerical methods are described for analyzing the characteristics of the air-chamber installed on a breakwater. One is the eigenfunction expansion method under the condition that the linear water wave theory is applicable. The method is useful, because the solutions give good agreement with the experimental results in the practical range and are able to calculate in short time. However the method cannot predict the loss and the theoretical maximum efficiency of OWC becomes 100%. The other method uses the computational fluid dynamics of Navier-Stokes equation in order to create the mechanism of the loss. It is predicted by the CFD that the source of the loss is the very large vortex generated in front of the air-chamber.

In the present paper the attention is focused on the effect of trailing edge serrations on aerodynamic sound radiated from Wells Turbine for wave power conversion. We discussed the effect of trailing edge serrations on aerodynamic sound radiated from two-dimensional airfoil. At the two-dimensional airfoil with trailing edge serrations, discrete frequency noise clearly observed at small attack angle. The effects of trailing edge serrations, rotational speed and blade number on the aerodynamic sound radiated from Wells turbine were also investigated. The overall level of SPL increased as the rotational speed of Wells turbine increased. The noise proportional to the rotational speed and its overtone components increased. The SPL of normal Wells turbine gave in agreement with that of trailing edge serrations for lower frequency band. On the other hand, the SPL of serrations was larger than that of normal Wells turbine for higher frequency band. The discrete frequency noise was not observed for lower frequency band.

A straight-bladed vertical axis turbine for wave energy conversion has been proposed in order to develop a novel air turbine suitable for oscillating water column based on wave energy plant. The objective of this study is to show the effect of guide vane shape on the performance of straight-bladed vertical axis turbine. The experimental study was carried out by a wind tunnel. The rotor has four straight blades with a profile of NACA0018, a chord length of 80.5 mm, a pitch diameter of 460 mm and a blade width of 490 mm. The guide vane consists of some arc plates. Further, flows around the proposed turbine have been investigated by use of MPS (Moving Particle Semi-implicit) method. It is found that the setting angle of guide vane θ suitable for the proposed turbine is obtained in the case of θ = -5°.

An oscillating water column (OWC) type wave energy converter is composed of a partly submerged wall, an air chamber, an air turbine and a generator and is considered to be safe even under the storm condition. Besides, an impulse turbine as the secondary conversion device in the OWC unit is expected to achieve the high efficiency. In the previous research, the authors investigated the effects of the air chamber length on the primary and secondary conversion efficiencies experimentally. Continuously, in this paper, the 2-D wave tank tests in regular waves for the performance evaluation of the fixed OWC type wave energy converter with the impulse turbine were conducted, and the effects of the impulse rotor inlet/outlet angle, the guide vane's number and the guide vane's setting angle are shown experimentally.

In the oscillating water column (OWC) based wave energy conversion system, a twin unidirectional impulse turbine topology has been suggested in place of the conventional unidirectional air turbine, in our previous studies. However, the average efficiency in the suggested twin turbine topology is considerably lower than that of the conventional unidirectional turbine because the reciprocating air flows can't be rectified adequately by the unidirectional turbine at the reverse flow. The present study aimed to discuss the usefulness of fluidic diode in order to improve the efficiency. The characteristics of fluidic diode under steady flow conditions were investigated numerically by computational fluid dynamics (CFD) analyses. Moreover, the effect of fluidic diode geometries on the turbine performance was discussed.

Wells turbine has long been used as an energy converter for wave energy conversion because of its simple structure. In order to alleviate the stall problem of this turbine, the authors have proposed a Wells turbine with booster for wave energy conversion. This unique power take-off consists of the Wells turbine for main turbine and an impulse turbine for booster. In the present, the turbine performance is estimated by the numerical analysis (CFD). As a result, the performance of Wells turbine for wave energy conversion can be improved by use of booster turbine at high flow coefficient.

This study presented the 1st conversion power performance evaluation of the floating wave energy converter considering the two-body system and the three-dimensional analysis and the time-domain numerical simulation. The comparison of the 1st conversion power performance between the one-body system and the two-body system in the one-dimensional simulation was also presented. The reactive control strategy was employed and the performance of the two-body system indicated the interesting character. The optimal control parameters those were calculated in the one-dimensional simulation were applied to the three-dimensional simulation and the result of the three-dimensional simulation was presented by comparing with the one-dimensional simulation.

We aimed to develop a small power Rankine cycle for suppling an auxiliary power by the hot spring water, which provides a small temperature difference from the ambient temperature. According to the results of the performance test of an actual scroll turbine, the mechanical efficiency of the turbine was approximately 30%. In the comparison among the three kinds of organic refrigerants, the cycle driven by R245fa indicated the lowest power consumption in the feed pump and the highest thermal efficiency. We pointed out the net output of the cycle was lower than that of the designed output, because the pressure did not reduce to the theoretical value due to the inherent pressure ratio of the volume type turbine.

A propeller hydroturbine can be used for tidal power current generation system and small hydropower generation. This kind of turbine will be installed near the water surface and wall. Therefore, the flow around the propeller turbine can be influenced by the boundary condition; free surface and wall. In the case of the small hydropower generation, a lot of propeller hydroturbines will be set in an open channel because energy generated by one propeller turbine is small. In this study, flow field near and downstream of the propeller turbine is clarified based on CFD result using the propeller turbine for an agricultural canal which is one of the open channel conditions. As a first stage, this paper shows effects of different analysis condition on the flow field around the impeller.

Recently, small hydro energy as one of sustainable energies has begun to spread for power generation. The small hydropowers are used in various complex flows, so it is difficult to predict the power performance appropriately. We proposed a one-dimensional performance prediction method of turbine installed at actual flow channels, which is to be used at early design/planning stages. This study investigated performance prediction for Darrieus-type hydro-turbine by one-dimensional streamtube model. As the results, the power coefficient is reduced along with the enlargement of the open channel width. In addition, effectivrness of inlet nozzle for power coefficient improvement depends upon the open channel width.

This study was focused on influence of nozzle shape and its layout on the performance of submerged impulse turbine. Because ambient water will affect the water jet issuing from a nozzle. It is considered that jet behavior will be drastically different between submerged and non-submerged jet. Two types of cutting angle at the end of the pipe nozzle, right angled and sharp edged, were tested. Reynolds number based on the nozzle diameter and jet velocity at the exit is 10⁵. PIV measurement was conducted for free jets and their velocity fields were compared. And the turbine performance was investigated for the nozzles and different impinging length from the nozzle exit to runner. As a result, it is revealed that the performance increases with decrease of the impinging length while the nozzle end shape has no influence on the performance.

Recently, it is attract rising attention that the plasma actuator technology can suppress a flow separation from airfoil surface. The objective of this study is to investigate the power performance and the flow field characteristics when the plasma actuator is utilized for HAWT's blades. In this study, the wind velocity around the HAWT model flow field is measured by a three-dimensional ultrasonic anemometer. The power performance of the wind turbine is also compared with and without the plasma actuator' excitations. The power coefficient in low tip speed region is improved by the plasma actuator' excitations. The tangential velocity component in the wake of rotor is also increased by the plasma actuator' excitations.

Studies on the wind turbine have been attempted because not only its mechanical performance but also acoustic noise becomes important issue. Regarding numerical modeling and simulation, researchers must precisely evaluate aerodynamic phenomena on limited memory and CPU resource. This paper presents several preliminary results from simulation of the NREL phase VI wind turbine, using a 3D-CFD-RANS turbulence model (Spalart-Allmaras and SST k-ω), and shows the comparisons between CFD results of 2 turbulence models and experimental results about pressure coefficient on a blade in the case the wind speed is 25m/s. These comparisons are made in the blade with 0° yaw angle, 3° tip pitch angle and 72 rpm (test sequence S).

A newly developed innovative wind / water turbine mechanism that is driven by longitudinal vortex is introduced. The blades of a conventional propeller type windmill with a horizontal rotation axis are replaced to the simple circular cylinders and a ring shaped plate is placed in the wake region. Once the propeller starts to rotate a certain direction, the longitudinal vortex appears stably behind the cylinder and the steady lift force is generated. It can rotate to the CW or CCW direction and the rotation direction is decided by the initial rotation direction. This new turbine is the simple structure, toughness and high torque feature. Therefore, it has a great possibility to use as a wind turbine to generate electricity even in the high speed wind without the pitch controller. It can apply for wider purposes, such as a turbine with high corrosion resistance and temperature resistance. We can also manufacture a micro-size turbine easier.

The performance of a novel wind turbine with a circular cylinder propeller driven by the longitudinal vortex generated near a wake ring plate is carried out. The rotation velocity of the wind turbine with a single circular cylinder blade propeller increases with increasing the wind velocity linearly when it exceeds a certain start wind velocity about 2m/s. It is affected by the normalized gap between the cylinder blade and the ring plate, s/d, and the width of the ring plate W/d. This turbine exhibits high torque at the row rotation velocity. The torque and power coefficients increases with increasing the number of the blades until the ten blades.

A novel wind turbine with circular cylinder blades, which is driven by the lift force produced by the longitudinal vortex. The wake ring plate with the eligible width is installed behind the cylinder in the wake region by retaining suitable gap distances between the cylinder and itself for employed the longitudinal vortex. In this study, the performance of this turbine is examined by using the numerical simulation. The predicting torque and the mechanical power from the CFD results are lower than the experimental data, however, the tendency of them correlate well with the maximum and minimum different as 23% and 2%, respectively. A longitudinal vortex occurs in the backside of rotation along the cylinder blade, which has a limited span wise length, and it induces the accelerating flow in the leading side. The rotating force is produced due to the different pressure gradient between rotation side and backside caused by the accelerating flow.

New airfoils for straight wing vertical axis wind turbine are designed using a genetic algorithm and two-dimensional vortex method aimed at improving the starting performance or the efficiency at a given rotational speed. Compared to a basic airfoil of NACA0018, these characteristics are improved in the optimized airfoils. It is also found that the change in the location of the aerodynamic center contributes to the increase of torque.

Seven miniature models with the diameter of 80 mm based on the butterfly wind turbine that is a lift-driven type and vertical axis type and one cross-flow wind turbine model of a drag-driven type were built by a 3D printer. Experiments for the measurement of electric power generation by using DC-motors equipped with the wind turbine models were conducted. The rotational speed under a constant wind speed did not depend on neither the kinds of DC-motors as the electric generator nor the value of the electric load resistance; that is, the rotational speed was decided by the wind turbine shape. The maximum electric power (262.5 μW at 6 m/s) obtained in this study was produced by the butterfly wind turbine model with outward-cambered blades. Since the maximum efficiency is small (0.041 %), the selection or development of a better motor as a generator fitting to the wind turbine model would be needed.

The objective of this study is to improve output performance of VAWT using Magatama blade. The method improving output performance is to place three guide vanes. The guide vanes were placed around upstream of VAWT. This study compared the performance of VAWT with the guide vanes with that of VAWT without the guide vanes in the experiment. The evaluation methods are to refer to the torque coefficient and the power coefficient. The experiment showed the guide vanes increased the torque coefficient about 3 times higher than that without guide vanes. The experiment shows the guide vanes increased the power coefficient about 6 times higher than that without guide vanes.

There are two types of VAWT, drag type and lift type. Drag type starts up in the low wind velocity, however peripheral velocity does not exceed the wind velocity. As for the lift type, peripheral velocity exceeds the wind velocity, however it does not start up in the low wind velocity. A new blade section, Magatama, has been proposed. Magatama blades may have both advantages of drag and lift type. Most of VAWT are fixed pitch type. It cannot recover enough wind power energy. To recover more energy, the VAWT with linkage mechanism is proposed. In this study, the VAWT with linkage mechanism was produced. The blade section of the VAWT is the Magatama. Proper blade setting angle was confirmed by numerical simulation.

This paper shows that the performance of the VAWT was evaluated in the high tip speed ratio at the field experiment. In addition, this purpose is the installation angle of the blade changed, and to examine the angle that windmill efficiency is most suitable. The field experiment is predicted that the tip speed ratio is increased by increasing the radiuses of the windmill rotor. The field experiment is carried out the high tip speed ratio could be measured the windmill output. The results showed a max power coefficient and a tip speed ratio was measured in blade installation angle of 60 degrees.

Cross-flow wind turbine has a characteristic of high torque coefficient at low tip speed ratio, good self-starting, low noise and high stability. Therefore, it attracts attention as the city type small-sized wind turbine for urban district. However it is serious problem that the maximum power coefficient is extremely low as 10% compared with other small-sized wind turbines. In this research, in order to improve the performance of a cross-flow wind turbine, a symmetrical casing is installed to it. Then the internal flow is investigated, and the effect of the symmetrical casing on the performance of the turbine is clarified by CFD simulation. Furthermore, effects of the corrugated blade on the torque distribution and flow condition are investigated.

In this study, differences of the dynamically measured torque of the wind turbine with a circular-arc airfoil and the static predictive torque based on the static wing characteristic of the circular-arc airfoil are investigated by wind tunnel experiments. There are actual setting angles that the static predictive torque accords with the dynamically measured torque for each azimuth angle on the geometric relations of the flow field and the blade. The tendency of the variation of the actual setting angle with respect to the azimuth angle is different between the upstream region and the downstream region. This suggests that a state of the flow field is greatly different between the upstream region and the downstream region. In the upstream region by using an appropriately fixed actual setting angle, static prediction torque variation calculated by using static airfoil characteristics is close to the dynamically measured torque variation.

The purposes of this study are to demonstrate numerically the droplet manipulation utilizing the Marangoni effect and to investigate the acting force magnitude and the flow relevant to the droplet movement. The analysis object is an oil droplet suspended in water (liquid-liquid two-phase flow). The liquid-liquid interface is captured by the Volume-ofFluid method, and the surface tension model we used here is the Continuum-Surface-Force method with considering the temperature dependency. We confirmed a quantitative agreement with experimental and theoretical results in terms of dependences of the driving force and velocity on the temperature difference and droplet diameter. We investigated the effects of Laplace pressure and thermal Marangoni convection on the droplet driving.

In order to investigate complex behaviors of suspended particles in liquid, we have constructed a confocal microscope system that enables us to measure the spatio-temporal distribution of micro particles. Three-dimensional visualizations of densely-suspended particles have been performed for an evaporating droplet on a glass substrate. In a droplet of water 99.9% and particle 0.1%, it is found that the particles mostly move along the substrate surface and assemble at the contact line. For a droplet of 33.3% aqueous ethanol solution, particles migrate along not only the substrate surface, but also the air-liquid interface. This implies that the flow inside a water droplet is induced by evaporation, while the flow inside a droplet of aqueous ethanol solution is strongly influence by the Marangoni effect.

We investigated the interfacial behavior and atomization of an acoustically levitated droplet. It is vital to understand the non-linear dynamic behavior of the acoustically levitated droplet in order to apply acoustic levitation method to the various scientific fields such as a material processing and analytical chemistry. The purpose of our study is to elucidate the generation mechanism of interfacial instability on the acoustically levitated droplet experimentally. In this paper, we recorded its time evolution from the interfacial deformation to atomization by high speed video camera and estimated quantitatively with three different liquid samples. Additionally, we investigated the detail of the atomization of the water droplet for better understanding of the atomization process. Our experimental data was compared with the existing theory. It is shown that the mechanism of the atomization of the levitated droplet is more complicated than the existing model indicated by the theory.

A droplet can steadily levitate over a moving wall owing to an air film under the droplet. Previous study obtained no quantitative agreement between the numerical and experimental film shape due to difference of dimensions. In this study, we experimentally investigate the flow field inside the air film. First, we calculate lubrication pressure generated inside the air film and then verify a local balance with surface tension and hydrostatic pressure. Second, we calculate two-dimensional flow field although previous study has assumed onedimensional flow field. Consequently, we experimentally confirm that the measured film thickness is lower than the numerical film thickness because some of the air escapes to spanwise direction.

A novel droplet generator equipped with flow-control has been developed for the formation of various liquid droplets. Two fast falling droplets with small angle are collided in air and are formed one droplet, which gets out of its shape from various type of oval to ball in falling by convection inside a small droplet. On the other side, two water jets with same speed and same angle are collided. But, one jet cannot be obtained by collision.

Ship's operating life is strongly influenced by the quality of anti-corrosion and anti-fouling coating of ship's hull. However, the quality and the efficiency improvement of the coating operation in shipbuilding are less-advanced. Aimed at improving the quality and the efficiency of the coating, observations of non-Newtonian (shear thinning) droplet impact and deposition were conducted. The observation results show the deposition is strongly influenced by non-Newtonian properties of the droplet.

Icing is a phenomenon by which super-cooled droplets impinge on a solid surface and accrete on it. Many studies on ice accretion have been conducted because icing phenomena cause serious aviation problems in various situations. Since there are many unknown physical properties of the super-cooled droplets, a detailed freezing process of super-cooled droplets has not been clarified yet. In our previous study, the static freezing process of super-cooled droplets of water was reproduced by numerical simulation. In this study, the dynamic freezing process is simulated in the case where a super-cooled droplet impinges on a flat plate in air. The obtained results indicate that our numerical method can reasonably reproduce the behavior of droplet freezing along the interface between the water and air.

The purpose of this study is to elucidate the effects of solidification on time changes in interfaces of an impinging water droplet. We carried out two-dimensional numerical simulations on the freezing of the droplet impinging on a cooling surface using a Phase-field method. The computational results show that the ice growth along the cooling surface and air/water interface started during the period of interface fluctuation caused by the impingement of the droplet. Eventually, the droplet became an ice particle with a small projection to the top. In addition, the temperature field was disturbed by latent heat transfer and the recirculating flow generated in the wake of the impinging droplet.

In gas turbines, melted particles are cooled and adhere on surfaces of turbine blades and endwalls. The deposition phenomenon results in decrease of turbine performance while its mechanisms are still unclear. In this study, the deposition phenomenon is investigated by means of three-dimensional numerical simulation with an adherence model by considering the latent heat. We have compared the obtained diameter of the adhesive droplet with the experimental data and confirmed that the present method can predict the droplet behavior well. Fingering shapes of the droplet are observed, which are also found in the experiments with the same condition.

The trajectory of liquid droplet rolling down on a tilted plate was controlled by the difference of triple-phase contact angle. The wall wettability was partly changed by using the cross-linkage of a polymer (PMC) on which ultraviolet ray is irradiated. Two kinds of geometrical patterns with different contact angles, i.e., saw-tooth and stepped pattern, were formed on the test plate and the behavior of droplet was observed experimentally on the wall of each pattern. The results showed that the droplet can be moved linearly with a constant angle to the gravitational direction. Considering the surface tension acting on the perimeter with different contact angles, the movement of droplet was analyzed theoretically. The calculated results approximate well the actual behavior of droplet.

We improve the accuracy and the numerical stability of the immersed boundary-lattice Boltzmann method (IB-LBM) to calculate the motion of a droplet on hydrophobic surfaces in complex geometry. To exactly derive the Chan-Hilliard equation, we use the proper source term proposed by Liang and the two-relaxation-time (TRT) collision operator. The series of the numerical tests, including Zalesak’s disk rotation, a single vortex, and a deformation of a sphere demonstrate that the computational effectiveness of the TRT collision operator is superior to that of the multi relaxation time collision operator. Analytical and numerical solutions of the symmetric shear flows demonstrate that the implicit diffuse direct-forcing method without the computational cost of the sparse matrix solver reduces the velocity slip and boundary value deviation as effectively as the implicit correction method for any relaxation times. The present IB-LBM with the TRT collision operator appropriately calculates the contact angle of liquids on the arbitrary shaped surfaces.

Three-dimensional simulation using an incompressible SPH method is carried out to investigate the scattering behavior of a liquid film flow spreading from the edge of a rotating disk. Computational domain is limited to a fan-shaped region near the edge of the disk using a periodic boundary condition in order to reduce the computational cost while keeping the spatial resolution as high as possible. The numerical results qualitatively agree with the experimental results though the number of ligaments is 1/2 to 1/3 of the experimental values. It is also found that droplets of nearly uniform diameters can be obtained by properly placing radial grooves at the edge.

Droplets impact are widely used in the cleaning step of semiconductor device manufacturing, however the detail of liquid film structure formed by the impact of drops is not clarified. In this study, we experimentally investigated behavior of liquid film which is formed by a droplet train impact. Especially, we focus on the diameter of hydraulic jump on a circular plate. The effects of nozzle diameter and liquid flow rate on the jump diameter were investigated. As a result, the jump diameters for the case of droplets impact were greater than that of liquid column impact. The hydraulic jump was observed under smaller water flow rate condition compare to the liquid column impact. In addition, the liquid film structure after hydraulic jump was affected by the circular plate edge and state of the jet.

The shape variation of a rotating liquid droplet is simulated numerically by solving the three-dimensional Navier-Stokes equations using the level set method. The rotation is imposed on the stationary spherical droplet, and the deformation of rotating droplet is observed. The droplet shape varies from a spheroid to a two-lobed shape, and breaks up finally. It is shown for the two-lobed shape that the droplet size increases with decreasing rotation rate. The relationship between the droplet size and the rotation rate is found to be in good agreement with the existing experimental data.

Interaction of atmospheric pressure plasma with a liquid film was investigated in order to understand a transport mechanism of chemically reactive species generated by the atmospheric pressure plasma in a liquid. The atmospheric pressure plasma produces a gas flow known as an ion wind. It has been reported that the ion wind induces the flow in the liquid. In our research, micro bubbles were generated in a liquid film under a streamer discharge. The internal flow was visualized using the micro bubbles as tracer particles. The micro bubbles were moved toward a discharge point on the liquid film edge under the streamer discharge. The micro bubbles were moved toward the grounded electrode in a corona discharge regime. The chemically reactive species generated by the atmospheric pressure plasma were detected in an optical emission spectra.

A technology for ejecting liquids is commonly used in an inkjet printing. However, previous method can eject only lowly-viscous liquid up to 20 mm²/s. Recently, we have proposed a new system for generating highly-viscous liquid up to 1,000 mm²/s. In our system, a wettable thin tube is inserted into a liquid-filled container and the liquid level inside the tube is kept deeper than that outside the tube. An impulsive force is applied at the bottom of the container followed by the application of highly-viscous liquid. In this study, we investigate its mechanism by using numerical method. We simulate the pressure-impulse field just after the impact and find that the difference of the pressureimpulse at the inner edge of the thin-tube decreases the liquid velocity inside the tube.

A highly-focused laser-induced liquid microjet is expected to be applied to a needle-free injection system. For practical use of this microjet, we need to control the volume V of the microjet. Previous research had revealed that the V is described by the maximum volume Ω of the laser-induced bubble. In order to manage the Ω, we have to investigate the describing parameters of Ω. In this paper, we carry out experiments to clarify the describing parameters of Ω. We find that Ω is proportioned to the laser energy E and inversely proportional to the distance H between meniscus and laser focus point.

Overfishing, catches of Japanese seafood, such as by changes and natural disasters of the natural environment is reduced year by year, and it is shifting to the fishery to grow from fishery catch. Whether or not the seed production is successful, it is how suppress the early mortality. Effect of water flow has been pointed out. However, it is nearly untouched state. In this paper, flow patterns in a circular rearing tank with some different PIV conditions are investigated by gas and liquid phase flow simulations with density function method.