In order to evaluate the joint strength between pure titanium and high-density polyethylene (HDPE), pairs of pure titanium plates with different surface roughness by polishing and pairs of pure titanium plates with KURACERA treatment were prepared. They were bonded with an HDPE sheet and subjected to tensile shear test. Each specimen was examined in terms of surface roughness and fracture morphology. As a result, it was found that there was a preferable range of surface roughness for paper polished specimens in which the joint strength was maximum due to large anchor effect, and KURACERA treatment significantly increased the joint strength. Cohesive fracture occurred in the specimens which showed relatively high joint strength, and large area of interfacial fracture or peeling was observed in the specimen with low joint strength. The joint strength of the KURACERA treated specimens was higher than that of the paper polished specimens. This may be because the surface geometry of KURACERA film was appropriate for the bonding.

Geckos have ability to climb easily and speedy up smooth vertical surface such as window glass. Gecko's foot has thousands of nanometer size hairs. They cause strong attractive van der Waals force. In present study, adhesion between surface structures similar to Gecko's foot is simulated by molecular dynamics (MD) method. Normal polyethylene (PE) molecules are vertically transplanted on a carbon plate. Two of this structure are interlocked like as zip fastener. The authors name this connected structure “Super Gecko model”. Simulated strength of Super Gecko model is a function of surface density of PE and temperature.

An aluminum alloy surface-treated with pure water was directly joined to a rubber containing different fillers to prepare a dissimilar materials joint. In order to study effect of filler on joint strength and joint state, a peeling test and observation for aluminum alloy surface before and after joining were performed in the dissimilar materials joints. There was a difference in the joining strength of the dissimilar materials joint depending on added filler. Microstructure formed by the surface treatment remained on the aluminum alloy surface in dissimilar materials joints after the peeling test, however its morphology was different depending on added filler. Therefore, it is speculated that the filler influences the surface morphology and results in different joining strength.

A method is proposed to simultaneously estimate adherend and adhesive thicknesses, and two interfacial stiffnesses for an adhesive joint. Numerical calculations on the model of the adhesive joint show that adherend and adhesive thicknesses can be evaluated based on notch frequencies of the reflection spectra. It was also found that there are some combinations of interfacial stiffnesses that give almost identical notch frequencies. The values of the two interfacial stiffnesses also affect the ratio of the reflection coefficients of the two adjacent notches. In addition, the present method was applied to the adhesive joints containing adherend contamination. The experimental results suggest that this method can be used to evaluate the thickness of adherend and adhesive. In the RA specimen, the interfacial stiffness of the interface with the release agent was less than that of the other interface in all evaluated cases.

The stress intensity factor of the edge interface crack is regarded as he intensity of the singular stress field at the interface end to reduce the singular stress in the interface end in adhesive joint. The edge singular stress in bonded plate can be reduced by adding the notch near the interface. In this study, the interaction between the crack and the additional notch is examined in order to evaluate the reduction effect of the singular stress. The stress intensity factor of the edge crack in a rectangular plate with semi-circular notch is analyzed by using FEM. The SIF ratios between the cracked plate with and without the notches are compared with the that of the bonded plates. From the calculation results, it is found that the interaction effect between the interface end and the notches can be roughly evaluated by the crack model with the notches although the crack length dependency.

It is important to reduce the singular stress at the interface edges to ensure high reliability of the adhesive bonding. In this study, a suitable shape of a semi-circular notch near the interface end is considered in order to improve the adhesive strength of single lap joint. From the FEM analysis, it is found that the intensity of the singular stress field at the interface end can be reduced about 20% due to the additional semi-circular notch.

Fracture of dissimilar materials is generally caused in the vicinity of the interface end. This is because the singular stress is induced at the interface end. In this study, in order to improve the adhesive strength, the adhesive bonded round bar with circumferential notch near the interface is considered. The small crack at the interface are strongly controlled by the singular stress field at the interface end without the crack. Then, the intensity factor of the interface edge crack. The effect of the position of circumferential notch on the stress intensity factor of the interface crack is analyzed. As a result, it is found that the singular stress at the interface end can be reduced significantly when the circumferential notch is close to the interface of the bonded bar.

The development of an ultra-flexible conductive connection has been attaching great attention, especially in the wearable electronics field. Next-generation wearable electronics is fabricated by integrating flexible electronics such as ultra-flexible power harvester and ultra-thin sensor. An anisotropic conductive film (ACF) is generally used for bonding each flexible electronics because it is easy to bond samples in ambient air with no additional process like heating and pressing. However, in the case of ACF bonding, the flexibility of integrated flexible electronics, especially in the bonding area, is lost due to the thickness of the adhesive of ACF is thick. Here, we show the new conductive bonding method with keeping flexibility by using argon plasma treatment. Just by overlapping two gold thin films after plasma treatment with no any adhesive, metallic bonds are created and the gold films are bonded together completely. Therefore, two gold thin films bonded by argon plasma bonding was exhibited high flexibility and half of contact electric resistance compare with ACF tape bonding samples.

Cold spray, which uses several tens micron size particles, is one of solid-state particle deposition technique. For making clear the deposition mechanism, it is necessary to understand the relationship between the particle deformation behavior and the local mechanical properties. In our previous study, microscopic deposition strength of the interface between cold sprayed coatings and substrates was evaluated by micro-tensile tests in FIB (Focused Ion Beam) apparatus. However, in the case of single particle deposition, it is difficult to take the micro-tensile specimens from the deposited particles. In this study, a new technique for evaluating the microscopic bonding strength between a single-particle and a substrate is developed. As a result, by using W(tungsten)-deposition as a function of micro-sampling system in the FIB, it was successful to make the micro-tensile specimens and to evaluate the microscopic deposition strength for the interface between single particles.

To improve the surface properties of magnesium alloys, dissimilar materials were joined to the alloy surface by shot peening. Magnesium alloy is the lightest of practical metals. Therefore, the range of use is expanding in the field of transportation equipment such as automobiles and aircraft. However, the corrosion resistance and wear resistance of magnesium alloys are considerably lower than those of steel materials. As the test material, a commercially available magnesium alloy was used. The dissimilar materials are commercially available pure aluminum A1050 metal foil and thermoplastic resin sheet. Their thickness is 0.02-0.1 mm. Shot peening was performed using a mechanical device. The shot material was a commercially available cast steel with an average diameter of 1.0 mm and a hardness of 445 HV. When joining aluminum foil containing one layer of resin sheet, joining was possible at a joining temperature of 300°C or higher. It was found that the aluminum foil had good bondability without peeling from the substrate.

Ceramics, which have excellent wear resistance, corrosion resistance and hardness at high temperatures, can be used for metal cutting tools and engine pistons. However, since ceramics are expensive, it is possible to reduce costs by joining with relatively inexpensive metals by friction welding. On the other hand, friction welding is a method employing the heat generated through mechanical friction between one surface in relative rotating motion to another surface, with the addition of a lateral force called "upset" pressure to plastically deform and hence join the two dissimilar materials. In this study, for the first time Al₂O₃ round bar and Al alloy (AC8A) round bar were joined by friction welding. The upset pressure was optimized to obtain successful joints. The microstructure at the interface region of joined materials was observed by a field emission scanning electron microscope. From the analysis results, we propose appropriate conditions for friction welding these two materials.

This study has developed a multiscale model which simulates stiffness reduction of interfaces of bolted and bonded joints. The multiscale model describes microscopic contact of asperities formed on the interfaces. A series of hammering tests and numerical simulations by the finite element method have been conducted. Various patterns of surface texture are given to the jointed interfaces of the specimen. The multiscale model is introduced as interfacial elements into the finite element model. The natural frequency of specimen obtained by the numerical simulations agree with the hammering tests. The bonded parts reduce the effects of the surface texture of the interfaces and the clamping force by the bolt and nut.

The butt dissimilar joints of Al-Mg-Si alloy A6063 and carbon steel S45C by means of friction stir welding (FSW) were prepared for investigated the effect of stress ratio on the fatigue properties of the joints. Fatigue tests were carried out under a condition of stress ratio R=-1. From the experimental results, it was found that the fatigue strength at 10⁷ cycles of the joint was around 80 MPa. This fatigue strength was significantly higher than that under the condition of stress ratio R=0.1. Two types of fatigue fracture occurred in this study. The first one was fracture at boundary between the lower hardness region and base material in A6063, and the last type was fracture around the welding interface. This tendency was similar to the results under the condition of R=0.1. Furthermore, plastic deformation around the fracture surface for the condition of R=-1 was not so significant as compared to that under the condition of R=0.1.

In this study, non-combustible magnesium alloy (AX41, Mg-Al-Ca-Mn alloy) and AA6061 aluminum alloy were joined by SPR (self-piercing rivets). According to observation of bottom surface at joint region, it was confirmed that short crack occurred when AX41 was used as a lower sheet. The cracks were induced due to poor formability of AX41 magnesium alloys at room temperature. The strength of joint was evaluated by tensile shear test. In the similar material joint, the maximum shear load of a AX41/AX41 joint was lower than that of AA6061/AA6061 joint. In case of the dissimilar materials joint, a joint showed higher maximum tensile shear load when AA6061 was used as a lower sheet. During the tensile shear test, crack occurred in the bottom of the lower sheet when AX41 was used as a lower sheet, and this crack affected the maximum load by causing pull out of a rivet from a lower sheet.

Alumina has long been known to enhance the strength of porcelain; however, the mechanism of strengthening is not completely understood. The strengthening in alumina-strengthened porcelain is examined on the basis of the change in thermal shrinkage of the porcelain matrix upon addition of various amounts of calcined talc. The increase in flexural strength of the porcelain due to the alumina addition increases with increasing difference in the thermal shrinkage between an alumina particle and the porcelain matrix. The increase rate of the flexural strength as a function of the difference in thermal shrinkage is described by the increase in nominal tensile stress required for the fracture of the porcelain due to the internal stress on the porcelain matrix. However, the strengthening due to the internal stress is not enough to describe the actual strength of the porcelain. Further strengthening appears to be achieved by the relatively large thermal shrinkage of alumina particles suppressing the formation of large cracks around quartz particles in the porcelain matrix.

In this study, a consolidation of a conductive thin plate from aluminum(Al)-doped zinc oxide (ZnO) powder was attempted by using the compression shearing method (COSME). The material properties of the sample formed by COSME and the uniaxial compressed sample were compared. Firstly, it was found that the color of the plate was changed to brown from white by applying the shearing strain, but still these were not transparent. In addition, bonding states of the samples were evaluated by an indentation hardness test method. It was clarified that the sample with higher hardness can be obtained by changing the shearing condition during COSME. By the XRD analysis, it was clarified that the crystal orientation of the sample was aligned by applying shearing strain. These results suggested that COSME can consolidate the Al-dope ZnO thin composite plate, but the consolidation conditions should be investigated for obtaining the transparent ZnO plate.

The environmental barrier coating (EBC) is applied to SiC-matrix composite materials, which are promising candidates for next-generation turbine blades of airplanes, so as to prevent wall-thinning by reaction with high-temperature water-vapor. As EBC comprises a multi-layer structure consisting of several layers of dissimilar materials with different material properties, EBC is expected to exhibit complex, severe thermal stress conditions. This study calculates energy release rate (ERR) for interface crack initiation and propagation by the finite element method (FEM) calculations with the aim to estimate conditions to prevent fracture by interface cracks under thermal stress due to cooling after fabrication at 1673 K. Our calculations suggested that the SiAlON layer be relatively thin while the mullite layer be thick to suppress crack initiation. It was also predicted that, with the thicknesses of the SiAlON and mullite layers of 5 and 20 μm, respectively, no crack propagation is expected as long as no initial cracks longer than 1200 μm exist.

Crack initiation and growth behavior in alumina ceramics under unbalanced thermal stress state was characterized by Disc-on-Rod (DoR) test. The thermal stress distribution was calculated using the finite element analysis from the temperature distribution recorded by an infrared camera. Using elliptical specimens, thermal stress ratio was well controlled by optimizing shapes of specimens and cooling rods. Furthermore, microfracture process was monitored by acoustic emission (AE) technique during thermal shock fracture. It was found that the maincrack was formed at the rapid increase in AE cumulative energy. It was also demonstrated that the maincrack was formed at the maximum stress point, on the direction perpendicular to the first principal stress. Finally, indispensable experimental technique for understanding thermal shock fracture in ceramic structures was well developed.

This research aims to simulate thermal distribution and deformation of composite heat insulation, which is usable as thermal expansion mats in catalytic converters for vehicles. Experiments are also carried out to determine material constants such as thermal conductivity and coefficient of thermal expansion (CTE) for each constituent material. The FEM simulations include a 2D plane-strain model representing a stacking structure with silica-fiber mats (SFM) and nano-porous heat insulation (NPI). NPI is inserted as a core-layer between two SFMs, and silicon carbide (SiC) is also added in NPI to prevent heat radiation. The analytical results indicate that the NPI core-layer has a significant thermal insulation effect on the whole model. The analytical and experimental results show a good agreement when the composite heat insulation is heated up to 500°C; however, the difference becomes evident above that temperature due to the influence of heat radiation from the heat source. Thermal shrinkage of the composite heat insulation can be predicted by the FEM simulations and compared with the experimental results. They suggest that the thickness of the composite heat insulation must be adjusted to be used in catalytic converters for vehicles.

Quantitative evaluations of the anisotropy of co-fired microstructures using FIB-SEM technique was studied using a new correction method during image processing. After the successful removal of the non-physical image distortion by means of this correction method, the distribution of pore orientation was analyzed. We found that due to the in-plane compressive stress arising near LSCF interface, the number of pores with a lateral inclination increases significantly during co-firing.

This study aims at numerical investigations on aerodynamic performance improvement of highly loaded low pressure turbine (LPT) airfoils by use of trailing edge device whose design concept is taken from Gurney flap for a racing car rear wing. The newly proposed device in this study, called localized Gurney flap (LGF), is a small protrusion on the pressure surface near the trailing edge. The purpose of the device is to reduce the secondary flow effects near the hub section of the LPT cascade with no severe additional aerodynamic penalties. Based on the original shape of LGF, DoE (Design of Experiment) is carried out to explore different types of devices that exhibit better performance than the original device numerically.

This paper presents numerical simulation of unsteady flows through three-stage stator and rotor blade rows in an actual middle pressure steam turbine while setting cutback first-stage stator blades and original stator blades. The shapes of original blades were measured from actual blades using 3D scanner during overhaul. Three different cutback length are considered to find out the influence on unsteady flows through the turbine blade rows and the performance of intermediate pressure steam turbines. The simulation employed numerical method developed by Tohoku University. The obtained numerical results indicate that the cutback stator blades certainly affected the steam flow velocity and outlet flow angle after the stator blade rows, resulting in a negative influence on the adjacent rotor blades, which depends on the cutback length.

Turbines are used in aeroengines and generators, and turbine blades generate power. In actual machine, the turbine is exposed to a harsh environment, so it is deteriorate due to factors such as thermal expansion, chipping, and wear. It is considered that the performance of the turbine blade and the flow field are greatly affected by the deterioration, and the efficiency is affected to a considerable extent. In this paper, in order to investigate how deterioration of the upstream stator affects turbine blade performance and flow field, a straight blade cascade test using a wake generator and CFD are performed. The wake of upstream stator can be simulated by moving a bar upstream of the rotor. The deterioration of the upstream stator can be simulated by changing the diameter of the bar, and the purpose of this study is to make a qualitative and quantitative comparison by investigating the influence of deterioration on the blade performance and the flow field around the blade.

A large-scale Wall-Resolved LES (Large Eddy Simulation) has been conducted for a transonic axial compressor rotor, NASA Rotor 37. By using a very fine computational grid of 1.35 billion points for a single passage and a high resolution scheme based on a 6th-order compact interpolation, the fine vortex structure in the turbulent boundary layer was resolved, and the interference between the shock wave and the blade boundary layer, and the boundary layer separation due to the shock wave interaction were clearly captured. The total pressure distribution at the rotor exit (station4) in the LES results was in good agreement with that in the experimental results, and the pressure deficit on the hub side was well captured in the LES results. The total pressure on the shroud side was slightly overestimated in the LES results, which is due to an underestination of the tip leakage vortex and its associated flow loss.

This paper presents a point-implicit relaxation algorithm to solve adjoint Euler equations simply and with a short-computing time on a shape optimization with a sensitivity analysis. The adjoint Euler equations are adjoint equations derived from Euler equations. And the sensitivity analysis reveals how the factors, which you focus on, change as the other factors change. In the sensitivity analysis, the relation between these factors is derived by solving the adjoint equations, and the process of solving the equations is treated as same as that of solving the governing equations related with the adjoint equations. On a shape optimization process, an implicit time integration method is better to introduce than an explicit time integration method to reduce the time until the convergence of the shape. And since we have to develop another numerical scheme to solve them, the algorism is desired to be simple. This paper shows how to develop the algorithm and how the algorithm performs.

The turbine inlet gas temperature has been rising with high efficiency and output power of the gas turbine engine. Turbine blade cooling is necessary to solve the problem of thermal fatigue. Film cooling technique is to protect the turbine blade surface with forming a protective film by cooling flow blown out from cooling holes discretely opened on the surface. It is important to improve film cooling efficiency by using a limited cooling flow rate. In this research, in order to develop high efficiency cooling hole shape, the cooling performance was evaluated by flow visualization, heat transfer experiment and PIV measurement. As a result, it was possible to confirm the high film cooling performance in the new original shape with tilted trailing edge.

Water spray characteristics are evaluated by a phase Doppler anemometer (PDA). PDA can provide the spray velocity and its diameter. The spray is tested in a wind tunnel which has 1m square plane and 2.5 m in length. The surround air conditions are 2.0 m/s of mean diameter, 33 degree Celsius of mean temperature and 60 % of humidity. The measurement planes are 100 mm and 600 mm from nozzle exit. A pin jet type nozzle which has a pin near the nozzle outlet hole is tested. One dimensional PDA system is applied for making measurements. Spray is spreading with the distance from the nozzle exit and then the data rate is decreasing from upstream to downstream. Mean velocities in the upstream is larger than that of downstream. In the downstream, the mean velocity profile becomes flat shape and it becomes almost the same as the air mean velocity. There is no clear tendency in the mean diameter and the Sauter mean diameter distributions. Differences in all data profiles for both vertical and horizontal directions are observed. This is caused by the unsteady and uneven spatial droplets distribution of the present spray.

An evaporative cooling system using ultrasonic vibrators has been proposed for the small centrifugal compressors in the micro gas turbine system, in order to decrease the compression work. The validity of the cooling system had been verified experimentally for the certain compressor. In order to clarify the extent of the validity of the system, a numerical analysis model is being constructed for the cooling system, which can be applied for various types of compressors. The present model simulates the evaporative cooling in the mist introducing duct (the inlet cooling), implying the physics of the advection and the diffusion of the mist, the vapor, the heat and the momentum of the air flow, as well as the evaporation. This paper shows the PIV measurement results of the advection velocity of the water mist introduced in the air flow duct, which can be used to verify and refine the numerical model. The results reveal the effects of the water columns produced by the ultrasonic vibrators, showing the deceleration of the longitudinal velocity in the near wake regions of the columns. Secondary flow component is found to change its distribution from the near wake to the far wake, which may bring large effects on the evaporative cooling in the inlet duct.

Wind turbines operate in large arrays in wind farms are facing issues of performance degradation and shortened fatigue life due to the wake ingestion. On the one hand, wind turbine wake aerodynamics include flow scales from turbine blade scale (mm) to turbine rotor scale (m) and wind-farm scale (km) which require computation methods capable of characterizing these scale ranges. On the other hand, simulating high Reynolds numbers and rotating turbulent flows calls for robust, high accuracy numerical methods and special mesh moving techniques. In this paper, we use the Multi-Domain Method (MDM) to divide the long wake computation domain into two shorter subdomains to improve computation efficiency and the Space–Time Variational Multiscale (ST-VMS) method for flow computations with Slip Interfaces (ST-SI) to enable mesh moving and maintain high resolution around turbine blades. We also implement Isogeometric Analysis (IGA) to increase the accuracy of computations. Computation results show the downstream wake evolutions in the near wake are in good agreement with previous experiments studies. The helical tip vortex pattern in near wake is observed by visualizing the velocity flow filed at wind turbine symmetric plane and vorticity with Q criterion.

The highly efficient air turbine is necessary in order to achieve a highly efficient wave power generation by oscillating water column system. A straight-bladed vertical-axis turbine is proposed to develop a novel air turbine that is suitable for an oscillating water column based on wave energy plants. The objective of this work is to study the effect of guide vane geometry on the performance of straight-bladed vertical-axis turbines. However, because of difficulty in visualizing the airflow around the vertical axis turbine by experimental fluid dynamics, the effect on the airflow of guide vanes proposed in Ref. (4) had not clarified. So, we considered the relationship between the airflow changes and the turbine performance by 2D RANS analysis based on the guide vane geometry proposed in Ref. (4). It is clarified that 2D RANS analysis can obtain the qualitative characteristics of vertical axis turbine. And the effects of guide vanes on the airflow were clarified. When installing the guide vane, the turbine efficiency was increased.

In recent years, in order to reduce environmental load, an engine that has both improved fuel efficiency and engine output has been demanded. To achieve both performances, downsize the engine and add a supercharger were performed. The supercharger allows for smaller engine displacements to produce much more power relative to their size. Also, smaller engines use less fuel to idle, and have less rotational which improves fuel economy. On a motorcycle development, these kinds of trials has been performed. Although carburetor is often replaced by injection on its development, superchargers for motorcycles have not been considered. In this study, at the first stage of development, we conduct numerical analysis of supercharger for a smaller engine for motorcycles,

Dissolved air in the working oil (Automatic transmission fluid: AT fluid) can cause problems by generating cavitation, which erodes the surfaces of parts, and bubbles. Therefore, it is important to measure the concentration of dissolved air in AT fluid. In recent years, there has been a need to measure the distribution of dissolved air concentration. The dissolved air in AT fluid can be estimated by measuring the dissolved oxygen (DO). However, conventional DO meters are point sensors that measure DO by placing the probe in oil and hardly obtain the 2-D distribution of it. In this study, we have developed an optical DO measuring technique using a pressure-sensitive paint (PSP) to capture the 2-D distribution of the DO in AT fluid. A newly developed oil-resistant PSP was able to measure the temporal variation in the distribution of dissolved air with high spatial resolution.

Centrifugal pumps have technical problems such as deterioration of pump performance and upward-sloping unstable characteristic in the head curve with low specific speed performance. In the present study suggested a new impeller in which radial and circumferential flow channels, conducted experiments and three-dimensional computational fluid dynamics analysis, and proposed hydraulic loss analysis based on the analysis results. As a result, the impeller suppressed an upward-sloping unstable characteristic in the head curve, and the best efficiency was found to be about 40% for a flow rate of 0.061 m3/min. Furthermore, it was also clarified that the impeller loss was dominant in the hydraulic loss and had a correlation with the flow field inside the impeller for each flow rate.

A left ventricular assist device (LVAD) is also used for right ventricular assist because a right ventricular assist device (RVAD) has not developed. LVADs should be driven at off-design point because the demanded head of a left heart is different from that of a right heart. When blood pumps are driven at off-design point, the instability of impellers can occur and lead to damages of blood. In the present study, the influence of the change of the attractive force due to the arrangement of the magnet on the movement of the impeller was evaluated in a RVAD under development was investigated. In experiments, performance tests of the RVAD were carried out and motions of the impeller were measured by two laser displacement sensors. As a result, changes in attractive force did not affect pump performance. It was also confirmed that the improved impeller operated more stably against disturbance. Therefore, it can be said that the improved impeller is more suitable for practical application.

In many small hydroelectric power, foreign matter obstruction is likely to occur because they use a runner with multiple blades. Therefore, the authors are considering using a single-blade centrifugal pump as a reverse running turbine. However, excessive radial thrust occurs by geometrically non-axisymmetric shape. Since previous studies have shown that the blade outlet angle has a significant influence on the fluctuation components of radial thrust in pump mode, this study investigated the effect of the blade inlet angle on radial thrust by experiment and CFD. As a result, increasing the blade inlet angle improved the turbine efficiency from the small flow rate to the middle flow rate, but the head coefficient increased on the large flow side and the turbine efficiency dropped rapidly. Even if the flow rate changes, the effect of the blade inlet angle on the time-averaged value of radial thrust is relatively small. On the other hand, the fluctuation component of the radial thrust increased on the small flow side as the blade inlet angle was large, but decreased from the medium flow rate to the large flow rate.

The common purpose for vehicle development has always been lowest fuel consumption. Automotive cooling fan shutter reduces the air resistance of the vehicle by controlling the amount of the air flow through the vehicle cooling system. The shutter proposed in this study consists of a diffuser and a stage of stator cascade with variable stagger angle of the blades, settled in the downstream of a fan rotor. An adequate stagger angle may improve the fan performance, due to the diffuser effects through the diffuser and the stator cascade. With large stagger angle of the stator, the cascade can be used as a shutter for the cooling system. The present paper reports the improvement method of the shutter shape, in order to increase the fan efficiency. The prototype shutter decreases the efficiency in the high flow rate range, although it increases the efficiency at the design point. The cause of the efficiency decrease has been investigated by the visualization test, and a new shape of the shutter has been designed with the help of CFD analysis. The validity of the shape improvement has been confirmed by the experiments.

This paper presents a control method of a check ball in hydraulic L-shaped pipe by Magnus effect. The spring-driven ball-type check valve is one of the most important components of hydraulic systems: it controls the position of the ball and prevents backward flow. In this paper, by using CAE tool, we evaluated the relationship between the position of the inlet pipe and the levitation time. By moving the position of the inflow pipe from the center of the housing, a strong swirling flow is generated in the entire housing to give rotational motion to the check ball. Magnus force was exerted by this rotation and it was found that the levitation time was advance. The check ball is arranged as a check valve in the L shape piping of the hydraulic cylinder. The check ball is supported by a spring to ensure the check operation. However, the spring must be eliminated due to various problems. This causes the check ball to rotate and translate. In the experiment, it is difficult to confirm the behavior of the check ball and the detailed flow around it. The purpose of this study is to clarify the effect of the Magnus force acting on the rotation of the check ball by using CAE tool. It was found that there is a difference in the time to check depending on the rotation direction and rotation speed of the check ball.

As international agreements to reduce greenhouse gas emissions such as the Paris Agreement has come into effect, the importance of renewable energy, for example, solar photovoltaic, wind power, and hydro power has increased. Hydro power is superior to solar photovoltaic and wind power in terms of generating a steady quantity of electric power. One of the types of water turbine is cross-flow, which is comparatively easy to customize turbine dimension, shape of blade, and the number of blade and so on. We have selected an undershot cross-flow water turbine which is appropriate for use at low water depths between upstream and downstream. We investigated the free surface flow patterns around turbine via both experiment and numerical analysis, and conducted a performance analysis based on the flow near the runner. Performance of turbine with straight blades arranged radially from the center point was greater than that of turbine with typical curve blades. We researched the effect of the number of blades on free surface flow patterns and performance of the turbine with straight blades. As the number of blades decreased, the time-average torque decreased and the difference of maximum and minimum value of torque increased.