The pressure measurement using a fiber optic prove hydrophone (FOPH) and the observation with a high-speed video camera have been conducted simultaneously to investigate the collapse of a laser-induced bubble near a rigid wall and the corresponding shockwave generation. Prior to the experiment of the bubble collapse near a rigid wall, the experiment for the collapse of the laser-induced bubble in bulk water has been conducted to investigate the applicability of the FOPH to the pressure measurement of shockwaves. The directivity of FOPH and the distance attenuation of pressure waves have been evaluated by controlling a directional angle to the spherical shockwave and a distance from a collapsing bubble. In the experiment of the collapse of a laser-induced bubble near a rigid wall, the peak value of the shockwave decays in inverse proportion to the distance, which shows the characteristic of a spherical wave propagation. Also, the pressure generated at the bubble collapse site estimated by the pressure measurement with FOPH and the water hammer pressure estimated by using the jet velocity obtained from the high-speed images tend to increase in proportion to γ (γ = s/R_max, where s is the distance between the boundary and the center of the bubble at the time of bubble generation and R_max is the maximum bubble radius), in the range of 2.25 < γ < 4.56. The pressure measured with FOPH agrees well with the water hammer pressures at lower γ numbers of 2.25 and 2.81.

Surface tension gradients due to concentration and temperature differences are well-known to trigger Marangoni convection. Marangoni effect is extensively studied for industrial applications such as welding and inkjet printing. In the present study, for a further understandings and development of non-contact liquid manipulation, the evaporation, spreading and self-atomization of droplets by Marangoni effect. We present the dynamic behavior of a pure or binary droplet containing a volatile component on an oil pool. To better understand the interplay between the evaporating droplets and spreading/atomization characteristics, the temperature field on the oil pool was visualized and quantified by IR camera. The Marangoni flow driven by the temperature gradient near the liquid film front was estimated and compared with the experimental spreading velocity. As a result, the experimental spreading velocity of liquid film was roughly agreed with the theoretical prediction.

Nebulization technology is used in various industrial and medical fields. One of the methods of spraying liquid is the ultrasonic mesh method, in which the liquid is pushed out of the mesh with many fine holes by ultrasonic vibration. Not only the shape of each mesh hole (nozzle) but also the hole spacing (pitch) determines the spraying quality and efficiency. Last year we conducted a numerical simulation of the droplet formation process from a single mesh hole by postulating axisymmetric flow and revealed the underlying flow characteristics. The present study focuses on the interference of liquid jets as well as the subsequent droplet formation process from multiple mesh holes. Numerical simulations were done for two models with nine truncated cone nozzles of 4μm outlet diameter with two different hole pitches of 20μm and 15μm, respectively. The ultrasonic vibration is operated at 200kHz. A stable droplet formation process was observed after the 4th cycle. When the hole pitch is relatively large, liquid jets slightly repel from each other. At a small hole pitch, the backflow in the negative pressure half-cycle becomes significant. Air accumulates inside the tank, and the liquid cannot be efficiently pushed out from the nozzle in the subsequent positive pressure half cycle. The interference between the generated droplets, the details of the backflow, and the retention of bubbles in the nozzle and the tank were clarified.

The optically induced Marangoni effect of a transparent liquid film with weak absorption on an absorbing solid substrate is investigated by means of linear stability analysis. The evolution of the film surface is described by a thin film equation. A linear dispersion relation is obtained by substituting a perturbed solution into the equation and linearizing the result with respect to the perturbation. The thickness dependence of the surface temperature of such a film is affected by both the absorbency and transparency of the film, and consequently, the stability of the film surface varies depending on the thickness and extinction coefficient of the film. The results imply that the surface is stabilized above a certain value of the extinction coefficient.

The melting process of ice is computationally examined. In this study, an ice (solid phase) is modeled by a very high viscous fluid and three-component immiscible liquid flows with surface tension are solved. The Moment-of-Fluid (MOF) method, is used to track the evolution of multiple interfaces. The numerical simulations are carried out by solving the conservation law equations for mass, momentum, and energy. The melting process of an ice with a cylindrical form is considered. From numerical results, it is shown that the melting process of ice can be successfully reproduced: the ice begins to melt at t > 0 and the solid phase near the heated plate changes into the liquid phase (water). The liquid phase flows and spreads in a radial direction with time. Finally, the solid phase fully changes into the liquid phase and the liquid phase widely covers the heated plate. As for temperature fields, higher temperature fields are formed in the region of gas and liquid phases and the cold temperature fields are maintained neat the solid phase. The effect of contact angle on the melting process is also presented.

Air pollution has been advancing all over the world, and PM2.5 is a threat to human body. As one of the solutions, air filtration technology aiming at removing fine particles is drawing attention. However, the filtration mechanism is complicated and there are many uncleared aspects. Therefore, numerical analysis is an effective tool for analyzing filtration phenomenon because it is possible to pay attention to individual movements of the fine particles and it is easy to change some important parameters. In this study, in order to investigate the effects of hydrodynamic, contact, and adhesion forces on filtration performance, we performed numerical analysis using a single fiber model that can analyze the phenomenon between particle and fiber in detail. The governing equation of the fluid was the Lattice Boltzmann method with an incompressible formulation. The virtual flux method was used to represent an object of arbitrary shape in a fluid. By changing the particle diameter to 2.0, 3.0, 4.0μm, the single fiber efficiency was then obtained and compared with the results of others. As a result, the single fiber efficiency tended to decrease as the Stokes number decreased. However, the difference of single fiber efficiency was larger compared to the results of others.

Three-fluid flows that single falling drops collide with immiscible liquid layers are numerically examined. This study is focused on the effect of physical properties of liquids on the dynamic motion of drop impact on immiscible quiescent liquid layers. In our computations, a Moment-of-Fluid (MOF) method is used to track the time evolution of the interface of three immiscible fluids, and two-dimensional axisymmetric computations are performed based on the MOF method. From numerical results, it is clearly shown that physical properties of liquids greatly affect the dynamic motion of drop impact on immiscible quiescent liquid layers. Especially, the effect of the viscosity of liquids on the drop impact is very large. Complicated and dynamic drop impact is observed when a drop with low viscosity impact on the surface of a liquid layer with low viscosity. At the same time, the dynamic behavior of drop cannot be seen when a drop with high viscosity impact on the surface of a liquid layer with low viscosity. The MOF method allows us to capture the dynamics of three-fluid flows.

Aiming at the formation of monodisperse micro-droplets, droplet formation in microfluidic flow-focusing devices with two different widths of the orifice is observed under the microscope. In the experiment, pure water is used as the dispersed phase and either mineral oil or silicon oil is used as the continuous phase to examine the influence of the viscosity on the droplet formation. The diameters of the generated droplets become smaller as the flow rate of the continuous phase increase and monodisperse water droplets with a minimum size of 6.5 μm is generated. The break up process might be classified into three regimes by the value of dividing the capillary number by the orifice width. At low capillary number, the dispersed phase blocks the orifice and breaks into droplets. Therefore, the diameter generated at the same velocity is smaller when the channel with smaller orifice is used. In addition, the diameter is reduced by using oil with a large viscosity as the continuous phase. Therefore, it is assumed that the shear force has a large effect on droplet formation. On the other hand, when the capillary number is high enough that the thread of the dispersed phase is thin and long and droplets are broken up at the downstream of the orifice, the effect of the orifice width on the diameter becomes small. The thread stretching by shear force seems to break up into droplets in an attempt to reduce surface energy. It is inferred that smaller droplets are produced by using oil with a large viscosity as the continuous phase and increasing the oil flow rate.

For long-time operation of general-use turbopump with inducer, instability-free operation is required as well as high suction performance in a wide operating range from shut-off to over flow rates. However, low frequency cavitation surge is known to often occur in low flow rate range, and it is hardly avoided because it is associated with the inlet backflow. In our previous study, we have tried to suppress the cavitation surge in a turbopump by installing an obstruction plate or a reduced-diameter suction conduit just upstream of the inducer. It has been found that the suppression of inlet backflow is effective in weakening/suppressing cavitation surge. However, in the both method, the effect is imperfect in the extremely low flow rate region. In the present study, to further suppress the inlet backflow, swirl breakers were combined with reduced-diameter suction pipe and its effectiveness was investigated by CFD. As a result, it was found that the inlet backflow is suppressed more remarkably by the smaller-diameter suction pipe equipped with swirl breakers.

Since many small hydroelectric power use a runner with multiple blades that do not have a dust removal facility, the increase in the cost of maintenance due to foreign matter obstruction is a problem. Therefore, the authors tried to use a single-blade centrifugal pump as a reverse running turbine and reported the effect of the blade inlet angle on radial thrust of this turbine, however the cause of the effect has not been clarified. In this study, we investigated the effect of the blade inlet angle on radial thrust and its constituent components by CFD. As a result, the radial thrust of the hydraulic part is relatively larger as the blade inlet angle is large, especially in the vicinity of θ*=180° in φ=0.037, and relatively smaller as the blade inlet angle is large, especially in the vicinity of θ*=90°～270° in φ=0.077, which greatly affects the difference in the fluctuation component due to the blade inlet angle. In addition, in φ=0.037, there is no significant difference in the direction in which the force acts on each blade phase angle in any component of β_b1=8°, 24°, but in φ=0.077, the pressure component of β_b1=8°, 24° acts approximately in the -120° direction in the direction in which the other two forces act.

A micropump is a type of small and precise pump, which is mainly used for fuel supply for small fuel cells and liquid transport for biotechnology and medical equipment. However, viscous micropumps are one of the most suitable micropumps to be driven inside the body, and their features include continuous transport of liquid and simple structure, which is advantageous in terms of manufacturing. In this study, we develop a viscous micropump that can be driven inside the human body using a helical shape and evaluate its performance by experiments and numerical calculations. The experimental method uses a motor to rotate a helical-shaped pump in a pipe filled with silicone oil. Then, the mass change of the silicon oil flowing into the downstream tank is measured by a load cell at each time, and the flow rate ṁ and the pressure difference Δp are calculated. For numerical calculations, Ansys is used to calculate the maximum flow rate, ṁ_max, and the maximum pressure difference, Δp_max, generated by the rotation of the two-wind helical geometry using a steady-state analysis with approximately 460000 meshes. Finally, in Re < 10, the maximum pressure coefficient has constant value. In Re > 10, the maximum pressure coefficient is increased with the increase of the Reynold number.

A detailed understanding of the characteristics of the flow field around small axial fans is essential to improve the performance and suppress aerodynamic noise of the fans. The feature extraction of the flow and acoustic fields around the fans enable us to obtain further understanding of them. In this study, the proper orthogonal decomposition (POD) and the dynamic mod decomposition (DMD) was applied for the high-resolution numerical data of the small axial fan. As a result, it was found that the waves were emitted from the root of the impellers and impeller, boss and the tip of the impeller or the gap between the impeller and the casing. Therefore, the aerodynamic noise source could be the tip, root of the impellers, and/or the gap between the impeller and the casing.

In this paper, a design concept for suppressing the leading edge separation and tip leakage flow is introduced in order to improve aerodynamic performance of a transonic centrifugal compressor. The aerodynamic design method used in the present study is an inverse design method based on a meridional viscous flow analysis. As the design concept, the blade loading distributions at the leading edge are reduced to decrease the incidence angles. In addition, the blade loading at the impeller tip side is suppressed to prevent the interaction between the leading edge separation and tip leakage vortex. The effectiveness of the design concept was evaluated by three-dimensional Reynolds Averaged Navier-Stokes simulations. The performance improvement was observed in the redesigned impeller compared with the conventional design impeller.

Generally, for centrifugal compressors with low specific speed, the wall friction loss accounts for a large percentage of flow loss. It is necessary to decrease friction loss in order to develop high performance centrifugal compressor with low specific speed. In this paper, three dimensional RANS analysis and smart visualization of CFD results are applied to two different centrifugal compressors with low specific speed, whose design specifications are same, however meridional shape and blade shape are different from each other. Flow loss generation mechanism in the centrifugal compressors is complicated, because many phenomena appear in the flow field, such as separation and various vortices. By inspecting entropy production rate, the flow loss generation in the two different centrifugal compressors was evaluated precisely, and the loss mechanism and the loss amount of each flow field are investigated quantitatively.

The effect of inflow condition and rotor tip clearance size on the stall inception in an axial compressor is experimentally investigated. The rig in this research is a low-speed, single-stage flow compressor, which has two types of tip clearance: design clearance (DC, ε = 0.5 %) and wide clearance (WC, ε = 2.2 %). The experiment is conducted in the different inflow conditions: the clean inflow and the distorted inflow. The rotor configuration is the forward-swept blade (Sweep). The stall inception is detected by applying a discrete special Fourier series analysis to the wall pressure trace data in front of the rotor blade. At the clean inflow condition, the type of the stall inception is modal-spike, regardless of the clearance size. On the other hand, at the distorted inflow condition, the type of stall inception of DC is modal-spike, and that of WC is spike. It seems that the difference of the stall inception between clearance sizes at distorted inflow condition is influenced by the circumferential distribution of the blade loading at tip region.

An optimization approach is presented that can be used to determine optimal parameter sets of a turbulence model in order to evaluate the Reynolds stress correctly. The approach employs the Ensemble Kalman filter (Enkf), which is one of data assimilation techniques and build by remodeling Kalman filter to estimate the initial state of nonlinear systems based on the observation state such as experimental result or high-accuracy simulation results. In this study, a target of the optimization was the parameters of k-ω 2 equations model which is one of the most famous turbulence models and widely used to design fluid machineries and analyze flow fields. Enkf was combined with URANS performed in a 2-dimensional flow field, and the observation state was the time averaged LES result which performed in 3-dimensional flow field and averaged into 2-dimensional flow field. Above flamework was applied to a transonic flow though the T106 A turbine cascade. The evaluation of this optimization approach was carried out with 3-dimentional URANS, and it revealed that the flow on the URANS using the optimized parameters showed a good agreement with the unsteady turbulent flow such as eddies that were not able to be recognized in the flow filed of the URANS using conventional parameters, so that the effect of the optimization was proved.

To improve the launch capability of rocket, rocket engine turbines are required to have high efficiency and high reliability. In reality it is quite difficult to achieve these two goals at the same time. In quest for highly efficient and reliable rocket turbine, the present authors have performed time-accurate calculation using Transient Blade Row (TBR) method of the commercial software ANSYS CFX to investigate unsteady flow behaviors in the two types of turbine stages (so called reference turbine and optimized turbine). This study then attempts to conduct detailed structural analyses of the 1^st and 2^nd stage turbine blades under the influence of unsteady fluid forces caused by rotor-stator interaction phenomena. Frequency response analysis is performed using the unsteady fluid forces calculated by ANSYS CFX, and the structural analyses are executed by use of MSC Nastran. In the analyses, two materials (Inconel 718 and Ti-6Al-4V) are adopted as blade material.

This study conducted PIV measurement of the flow of the suction surface of low pressure turbine for aeroengine. In the past, various researchers have investigated the change in turbulence kinetic energy (TKE) and production terms in the TKE equation due to periodic wake passing, however there are few survey examples using PIV measurement. Therefore, we measured the flow field of the boundary layer using a large-scale linear cascade test equipment with a wake generator. In the steady condition, turbulence statistics, such as TKE, reynolds stress and value of production term in the TKE equation were increased by vortex roll-up. On the other hand, in the unsteady condition, they fluctuated due to the periodic wake flows.

The study proposes a new flow control device (FCD), called one-side FCD or OFCD, to Improve conventional cooling hole film effectiveness of turbine airfoils for gas turbine. Experimental examinations are conducted using PSP (Pressure-Sensitive Paint) method to verify the predictability of film effectiveness by the present calculation. It is found that OFCD performs fairly well.

A gravitation vortex type water turbine is a water turbine that guides water into a tank and generates power by the gravitational vortex generated in the tank. Although this water turbine can be generated by a low head and a smallness flow, the flow field is a complicated thing which has a free surface. We researched Influence of number of blades on performance and flow field of this water turbine a circular tank. However, influence of number of blades on this water turbine with a volute tank with improved performance has not been elucidated. In this study, we performed the free surface flow analysis of this water turbine with a volute tank and investigated performance and flow field with each number of blades. As a result, the turbine efficiency of this turbine was highest when the number of blades was 20, and showed a tendency different from that of the circular tank. In addition, as the number of blades increased, the loss inside the impeller increased sharply, but the loss at the outlet of the tank decreased significantly. Therefore, when the number of blades was 20, the total hydraulic loss was the smallest, and the hydraulic efficiency and the turbine efficiency were the highest.

The decommissioning of nuclear power plants is becoming a very important issue in the nuclear industry, as more and more nuclear power plants in Japan and abroad have been in operation for more than 40 years. In decommissioning, it is necessary to improve the decontamination technology for the structures of nuclear facilities to reduce the amount of radioactive waste to be managed and disposed of. In the decommissioning of the “Fugen”, which is the prototype of a advanced converter reactor that was shut down in 2003, a dry decontamination system for small diameter pipes, which are difficult to decontaminate, has been introduced on a trial basis and has been highly effective. However, the detailed decontamination mechanism of this dry decontamination device is not yet known, and basic research on this device is an important issue to be addressed in order to improve its efficiency and reliability. In this study, a dry decontamination machine was divided into two sections, one for blast polishing and the other for barrel polishing, and the results showed that blast polishing was more effective in decontaminating metal samples. The effect of blast polishing was measured at different angles of incidence, and it was found that blast polishing was most efficient at a projection angle of 45°, and it was confirmed that the effect of indentation rather than polishing increased as the angle was closer to 0°.

The performance of an automobile engine is affected by the shape of combustion chamber and intake/exhaust system. In particular, flows in a cylinder are affected by the shape of the intake/exhaust pipes and the valve timing. The swirling flows generated in the intake stroke affects combustion speed and combustion stability. In this study, we focused on the tumble flows and performed numerical simulations by modeling piston-cylinder section of a four-stroke engine. The flows in a cylinder were considered by using compressible Euler equations. The virtual flux method was used to express the shape of the engine on a Cartesian grid. Effects of the valve lift on the tumble flows were investigated by using the tumble ratio. As a results, the tumble flows increased because both tumble ratio and turbulence intensity increased when the valve lift was small.

Porous media is attracted attention for heat exchangers to improve system performance. In this study, to apply a magnetic fluid as a working fluid in the heat transfer system with porous media, the flow behaviors of the magnetic fluid flow via the ceramic foam porous media by applying a magnetic field were investigated experimentally. The experiment was performed in a rectangular duct, and a water-based magnetic fluid was used as the working fluid. The magnetic fluid flows through a ceramic porous media with a pore density of 13 pores per inch. The Reynold number based on the hydraulic diameter of the test section, Re_Dh, is varied in the range of 100-1500. The magnetic field is applied at the center of the porous media in the test section, and the magnetic field intensity is 100 and 300 mT. Pressure drop and heat transfer coefficient with and without the magnetic field are measured to discuss the relationship between flow resistance and heat transfer. As the result, the flow behavior is quite different between with and without porous media. In the case of magnetic fluid flow through the ceramic foam porous media, the heat transfer is enhanced by applying magnetic field and this enhancement becomes weak with increasing Re_Dh, while the pressure drop increases by applying magnetic field and increasing ratio is almost constant with Re_Dh.

In this study, temperature-sensitive magnetic particles were microencapsulated with fluorescent dyes to create a multifunctional working fluid. In this experiment, the microcapsule particles obtained from the in-liquid drying method were dispersed in water together with a surfactant, flowed through a visualization channel provided with a magnetic field, and the flow phase was observed. The visualization channel is made of cycloolefin polymer. An observation unit was provided in the center of the flow path, and the excitation light was irradiated to excite the fluorescent dye encapsulated in the microcapsules, and the fluorescent transmitted through the two types of filters was observed. When a magnetic field was applied, clusters were formed in the channel. This cluster grew over time. At the same time, the process of cluster migration and growth were observed near the wall surface. Furthermore, the experiment was conducted by changing the flow velocity and magnetic flux density. As a result, the cluster length decreased monotonically due to the increase in the flow velocity and the decrease in the magnetic flux density in the magnetic field supply section. In addition, by heating the flow path, the magnetization of the temperature-sensitive magnetic particles in the microcapsules was also reduced, and cluster formation was suppressed.

Cellulose Nano-fibrils (CNFs) which are extracted from wood fibers have gained great attentions as a novel biological material. Because mechanical properties of cellulose filament made of CNF increase with its orientation, the orientation control is essential in the material fabrication. In order to evaluate the effect of channel configuration on the orientation of CNF, the orientation process was clarified by numerical simulation. Firstly, the flow field analysis was performed for two microflow channels with different flow focusing angle of 90 and 45 degrees for various flow rate ratios between main flow and focusing flow. Then, using the obtained results, the order parameter of CNFs were evaluated by solving the Smoluchowski equation with introducing the orientation distribution function of CNFs. As a result, the higher CNF orientation parameter can be obtained for the channel with 45° focusing angle and the orientation is enhanced also by increasing the flow rate ratio. Single cellulose filaments were fabricated under optimal conditions predicted by numerical simulation, and material properties were evaluated by tensile testing. It was shown the strength of the single filament was improved under the optimum condition with 45° focusing angle.

When a propeller is replaced by a circular cylinder and a ring-shaped flat plate is installed in its wake coaxially to the rotation shaft, a longitudinal vortex forms the intersection area. It generates lift force on the cylinder blade and drives it to rotate as a wind turbine. In this study, the influence of the shape factor on the transient response of the rotation recovery from sudden change of the rotation speed is experimentally examined. The rise time that is defined by the time from the cessation of force to keep a certain rotation speed to the achievement of the steady-state is measured. The rise time of the circular cylinder wind turbine is shorter than the vertical axis traditional wind turbine. The rise time for the transition from a lower rotation to a higher steady rotation is faster compared with the response of the opposite conditions, that is, from a higher to the lower steady rotation.

The characteristics of wind direction of horizontal axis cylinder blade wind turbine driven by longitudinal vortex was examined. The wind tunnel experiments were carried on the determination of the effect of the angle between the wind turbine rotation axis and the free stream on the power coefficient. It is found that there is a critical yaw angle where the power coefficient drops sharply. For the lift force generated by the longitudinal vortex, the peripheral velocity of the cylinder blade and the relative angle of attack formed by the free stream are important. The distribution of the torque as a function of the rotation angle of the blade was evaluated. It is clarified the fluid force acted on the blade related with the relative attack angle, but it was caused a region of the rotation angle where the necklace vortex was varnished.

A horizontal axis wind turbine has been developed to more sophisticated design. For the design, numerical calculations are developed, which like as blade element and momentum theory, vortex method, RANS and LES. The paper investigates the usability of hybrid method of strip theory and LES to design one. The wind turbine is designed based on MEL002 blade through standard blade element and momentum theory for the design conditions - upstream flow velocity 7m/s with tip speed ratio 2.5 and angles of attack 10 and 15 degrees. The hybrid LES calculates power coefficient and flow filed. As the results, the power coefficient by the present LES at design tip speed ratio 2.5 agrees with the experimental result. Furthermore, the separation region around the blade with angle of attack 10 degrees is smaller than one with 15 degrees. The flow simulation can show the reason that the power coefficient of 10 degrees is larger than one of 15 degrees in experiment.

Performance improvements in Vertical Axis Wind Turbines (VAWTs) are expected for small-scale power sources. The Savonius wind turbine, which is a representative example of VAWTs, is characterized by various advantages such as simple design, independence of wind direction, and small footprint. However, due to generation of a negative torque by the returning blade the Savonius model suffers from low efficiency. The Ugrinsky wind turbine allegedly produces higher output than the traditional Savonius turbine, yet any recent studies cannot be found. Thus, investigation on the Ugrinsky wind turbine was conducted, and the evaluation was carried out by comparing it to the Savonius wind turbine. The flow around the turbine was simulated by using the regularized lattice Boltzmann method. The virtual flux method was used to describe the shape of the turbine on a Cartesian grid, and the multi-block method was used for local fine grids of the turbine. The rotational speed of the turbine was maintained constant, and its performance was evaluated by the output power and torque coefficients. The results show that the Ugrinsky model achieves a higher power coefficient value by 43.2% compared to that of the Savonius model. Furthermore, unlike the Savonius model, the Ugrinsky counterpart maintained a positive torque coefficient value throughout a cycle at the tip speed ratio of 0.5.

Wind power generation has a potential as an environmental friendly energy. Small wind turbines have attracted attention for installation as an effective utilization for natural energy and emergency power supply. Our research has been focused on the compact Darrieus type (straight bladed Gyro-mill type) vertical axis wind turbine using elastic wings on morphing technology. Three different types of materials, PET (Poly-Ethylene Terephthalate), aluminum plate and stainless steel plate were used for auxiliary wings. The maximum tip speed was obtained in the case of aluminum plate at 1.0 mm plate thickness. As a result of the performance experiment with loading, the unique phenomenon is observed by the auxiliary wing deformation. The unique fluid motion can be discussed by analyzing image tracking.

A wind-lens turbine has been developed as a high performance HAWT. To investigate the effect of turbulence intensity on the wind turbine, the paper shows the power and torque coefficient in the steady wind of mean velocity 7 m/s with turbulent intensity 2.4% and 4.3%. The turbines are made based on the two blade types - NACA 63xxx and MEL002. As the results, the power coefficient of the wind-lens turbine is more than 1.8 times as larger as one of the rotor only wind turbine. In particular, the MEL type wind-lens turbine has flat distribution of power coefficient in the wide range of tip speed ratio from 2.5 to 4.0 than NACA’s one. The characteristic shows as a high-performance wind turbine.

In Japan, wind farms are often constructed on a complex terrain. However, the wind that flows into the wind turbine on the complex terrain is complicated. In this paper, the influence of the terrain on the wind turbine power output was considered from the wind turbine measurement data and the wind condition analysis using numerical analysis. From the measured data, the wind turbine power output changes depending on the wind direction, which turbulence intensity changes even if the average wind speed is almost same. From the numerical analysis results, the wind characteristics change due to the influence of the terrain configuration depending on the wind direction. As the results, it is considered that the wind turbine power output is affected by wind characteristics due to complex terrain.

In order to explain the phase-synchronization of the blades of a vertical axis wind turbine (VAWT) pair, which had been observed both in the wind tunnel experiments and in the computational fluid dynamics (CFD) analysis, a mathematical model that considers the pressure fluctuation due to the interaction of blades is proposed in this study. The analysis using the model shows that the phase-synchronization can occur with the same synchronous angular velocity in the two symmetric arrangements even without considering the induced velocity caused by the rotation of VAWT rotors and that the fluctuation period of the angular velocity becomes longer as the interaction increases. Furthermore, when the effect of the induced velocity is added, the model calculation gives the result which is qualitatively consistent with the gap dependence of the synchronous angular velocity observed in the experiments and CFD.

Wind turbines in cold climates are defined as wind turbine operating in an environment where the temperature below the operating limit temperature (-10℃) of a standard wind turbine and /or meteorological icing occurs to the wind turbine . In this paper, the aerodynamic characteristics change due to icing is determined based on the IEC standard. The wind turbine performance and the load of icing airfoil was clarified by numerical analysis. Also, the effect of icing on the reduction of rated power was evaluated. As result of the analysis, the wind speed that shows rated power of wind turbine with icing airfoil is higher than that without icing, and the maximum thrust with icing airfoil is higher. Also, the optimum limit rate of the rated power with icing airfoil was estimated by a view point of the maximum thrust.

This study proposes a straight-bladed vertical-axis turbine for ocean-wave energy conversion. The aim is to develop a novel air turbine suitable for an oscillating water column in a wave energy plant. For the purpose, the performances of straight-bladed vertical-axis turbines were investigated for different guide-vane geometries in a wind tunnel experiment. The rotor has four straight blades with an NACA0018 profile, a chord length of 80.5 mm, a pitch diameter of 460 mm, and a blade width of 490 mm. In this study, the guide-vane geometry was varied as arc, semi-arc, and semi-arc with two types of straight part. Under steady flow conditions, the turbine performance was evaluated by determining the input coefficient, the torque coefficient, the flow coefficient, and the turbine efficiency. The semi-arc blade geometry decreased the input coefficient and improved the starting characteristics of the turbine. Moreover, the semi-arc blade and the semiarc blade with a straight part improved the turbine efficiency over a wide range of flow coefficients.

In this study, a pump system using wave energy was developed for generating power of pumping the seawater, which can be used for the preservation of farming conditions of marine products and the replacement of seawater by pumping of the deep water. A radial pump that can be operated by an impulse turbine for wave energy conversion was developed, and the performance of this pump system was investigated experimentally. The thick-blade impulse turbine used so far was changed to a thin-blade impulse turbine. The torque decreased slightly, but the same tendency was confirmed for the thin-blade impulse turbine. In the closed flow path, the head decreased and the flow rate increased, but the pump efficiency decreased due to the influence of the pipe flow resistance.