A twin-impulse turbine for bi-directional flow has been developed for wave energy converter. However, the previous studies elucidated that the mean efficiency of the twin turbine is much lower than that of the impulse turbine for a unidirectional flow because a portion of airflow passes through the reverse flow turbine whose efficiency is very low. Therefore, a fluidic diode was adopted in the twin-impulse turbine in order to reduce the air flow through the reverse flow turbine. In this study, the rectification effect of the fluidic diode was investigated where a bypass is introduced into a blunt body. A computational fluid dynamics (CFD) analysis was conducted to investigate the effect of fluidic diodes on the turbine performance. In this analysis, RANS equations were used as the governing equations and the standard k-ε model was used as the turbulence model. The computational domain is composed of a circular tube and fluidic diode, and the domain meshed with an approximately 1.5 million mesh elements. As a result, it was found that the rectification effect of the fluidic diode is enhanced by installing a blunt body with a bypass hole of diameter 20mm and 16o taper angle.

Wave energy can be converted into the electrical energy by using the oscillating water column (OWC) device with air turbine. An impulse turbine for bi-directional flow, as an air turbine in the OWC device, can be obtained a high torque in a wide range of flow coefficient, it has a bit of complicated structure though. Therefore, an impulse turbine with a simple cascade for bi-directional flow was employed in order to overcome the drawback of the complicated cascade, and its performance was investigated by using computational fluid dynamics (CFD) analysis. As the results, the impulse turbine with simple cascade showed peak the efficiency of η_p=0.479 at a setting angle of the guide vane θ =15°, inlet (or outlet) angle of the rotor of γ =80°, solidity of the guide vane of σ_r =2.02, and solidity of the rotor of σ_g =2.27

Cross-flow turbine is widely used for run-off river small hydropower generation because of excellent partial load characteristics with lower manufacturing cost. So far, there have been various studies to improve turbine performance. The authors have proposed a new shape cross-flow turbine which has a cylindrical cavity and a guide wall at the end of the outer wall of the turbine nozzle to control the outflow direction from the runner passively. On the cross-flow turbine with a guide wall, the authors evaluated the performance, internal flow behavior, vibration of the turbine with or without the cavity between the outer wall of the nozzle and guide wall. As a result, the flow direction from the runner outlet depends on the runner rotation speed and guide vane opening. The cavity is useful to suppress flow separation from the top edge of the guide wall for various rotation speed and the guide vane opening and to improve the turbine performance. The effect is more significant under higher runner speed and smaller partial load operation. Besides, the turbine vibration becomes smaller by the cavity with the decrease of the guide vane opening.

In order to design a large-scale wind farm, it is highly important to understand the wake of multiple wind turbines. Wind tunnel experiments with two arrangement patterns were conducted to approach the interference of the wakes arranging two wind turbines. Results have shown that when the blade posisions of the two scaled Horizontal-Axis Wind Turbines(HAWTs) overlap, the output coefficint of the downstream wind turbine greatly reduced. Wind velocity distribution measurement of the rear of two scaled HAWTs was perfortmed at the hub height by using a ultrasonic anemometer and confirmed that the speed recovery in the wake was enhanced in the two wind turbines configration. Inaddition, computational fluid dynamics simulations were carried out and it was found that the occurrence of the wake fluctuation was accelerated in the two wind turbines configration.

A new non-destructive and non-destructive cell type identification method combining ion transport and electrical impedance spectroscopy (EIS) is proposed. The transmission coefficient P [m/s], calculated by combining data of the electrical impedance spectroscopy (EIS) experiment and ion transport model, represents the ability of ion transmembrane transport to be used to identify cell types. In the experiment, sucrose aqueous solutions with different sucrose concentrations were used to prepare cell suspensions to simulate the state of cells in hypertonic, isotonic, and hypotonic solutions. The cell suspensions with different osmotic pressures are measured by the EIS method on the frequency from 2000kHz to 2MHz. Numerical calculation results show that osmotic pressure has an effect on the ability of ion transmembrane transport. In the hypotonic solution, the larger P value means the cells release more ions compared to an isotonic solution. Conversely, in hypertonic solutions, the smaller P value means cells release a small number of ions compared to isotonic solutions.

Fibrous beds have been used as filters in various engineering and medical processes. In recent years, attention has been focused on the behavior of substances that move in fibrous media such as collagen gel and Platelet-rich-plasma filter. We examined the motion of microparticles in the Stokes flow field where Re is extremely small. The behavior of particles passing through the fibrous bed was calculated by Stokesian dynamics method. The fibrous bed was modeled by particles and four kinds of structures (mono-layer with fiber volume fraction φ = 3%, 5%, and combined bi-layer with φ = 3%-5%, 5%-3%) were considered. It was found from the simulation results that the larger the fibrous volume fraction, the more moving particles are trapped. The standard deviation of the average moving distance of each particle indicated that the particles spread on moving through the fibrous bed. Such spreading behavior is attributed to the hydrodynamic interaction that can be seen in the Stokes flow. It was also found that the magnitude of the spreading depends not only the fiber volume fraction, but also the structure of the fibrous bed. It was suggested that the structure of the fibrous bed, particularly the combination and arrangement of the upper and lower bed, substantially changes the motion of the particles.

Swallowing disorder has been becoming a serious issue with increasing in elderly people. Disorder sometimes appears with a decrease in saliva, because saliva has an important role in lubrication over the oral cavity and throat. Though the structure of biological mucosa has been studied physiologically, there are only few studies that examined the influence of its oral and throat mucosa on fluid lubrication. Therefore, we investigated the friction reduction effect on the oral cavity and pharynx. There is a thin liquid phase with a thickness of about 0.1 mm called saliva layer on oral and throat mucosa. It is necessary to evaluate the rheological properties of mucus with low viscosity and high spinnability like saliva layer using a PEO solution, because of the viscosity characteristics different from the shear viscosity. The PEO concentration was determined from the measurement of the viscous characteristic by the rotational viscometer to set the same viscosity as that of saliva. Therefore, we investigated the rheological characteristics by measuring the extensional viscosity to make a mucus using a PVA coating. We measured friction torque on the artificial mucosa lubricated by PEO solution. The effect of friction torque of high-viscosity liquid foods on the artificial mucosa was clarified in this study. We considered a slip occurs in the saliva layer.

The ocean occupies 70% of the earth, and there are many unexplained parts such as deep sea and aquatic organisms. For these reasons, it is required to improve efficiency of autonomous underwater vehicles (AUV) for the purpose of investigating undeveloped areas in water. As part of this, many studies have been conducted with the aim of making clear the physical mechanism of swimming of aquatic organisms. Aquatic organisms are thought to select the optimal body shape and swimming pattern according to the swimming environment in which they live. Therefore, in this study, we investigated the effects of fish body thickness and swimming pattern on propulsion performance such as swimming speed and swimming efficiency using numerical analysis. There are various parameters in the equation that determines the swimming pattern, and this time, the relationship between the swimming pattern and the thickness of the body was considered by changing the parameter s₄ that determines the position of the node in body. As a result, the closer the node is to the head, the higher the average swimming speed in all models with different body thicknesses. On the other hand, the amplitude of swimming speed and the rotation angle around the yaw axis were increased, resulting in unstable swimming. It was also suggested that when the body is thin, it is strongly affected by the difference in the position of the nodes.

Red blood cells (RBCs) have high deformability and change their shape under the influence of various external factors such as the difference in osmotic pressure inside and outside the cells. In a hypotonic solution, where the osmotic pressure is lower than the blood, RBCs swell since the external water penetrates into the cells through the semipermeable membrane. If the membrane hole appears as a results of excessive swelling, internal substances (hemoglobin, etc.) leach out of the cells (hemolysis). We have focused on the osmotic resistance of human RBCs, and investigated the swelling and hemolysis phenomena caused by the hypotonic solution experimentally and numerically. In the experiments, there was a tendency that the RBCs swelled from biconcave to a spherical shape and then slightly decreased in volume. After that, the hemoglobin in the cell leached into the outer solution, indicating the hemolysis. To acquire a piece of information such as the time change of the membrane surface tension which is tough to measure, we reproduced by a simulation the swelling and expansion phenomena. As compared with the experimental results, the simulation results showed less volume change and shorter time scale, but the overall tendency was similar. In the future work, it is necessary to confirm the validity of the simulation by comparing a number of other experimental results.

We have developed a microporous covered stent (CS) for the endovascular embolization treatment of intracranial aneurysm (IA). This stent promotes progressive thrombosis by flow diversion and facilitates IA embolization treatment by clotting of whole blood in the IA. Because it is difficult to quantitatively evaluate in vivo embolization performance of CS, we have been developing a model blood which can produce clot like red thrombus by using hyper-coagulable skim milk. In this study, the embolization device performances were evaluated by using our developed model blood. The saccular IA model was placed at the outer wall of a U-bend vessel model of which curvature was almost same as that of human internal carotid siphon. The IA opening position at the U-bend vessel model was located at θ = 60, 90 and 120 deg. Reynolds number of the flow in the U-bend vessel model was set at 580, which was mean Reynolds number in the human internal carotid siphon. FD model (pore diameter: 74μm, aperture ratio: 53%) was placed at opening of IA model. The model blood clot forming and growing process was visualized by colored die injecting and clotting volume in the IA was measured by image processing of the time tracking color-die images. As a result, model blood clot was formed locally caused by flow diversion caused by FD model stenting. These results suggest that the embolization performance is able to be evaluated quantitatively.

Tail fin of fish and frog webbing are like concave polygonal shape. The objective of this study is to understand the drag coefficient of concaved solid disc and visualization of structure behind disk. We are focusing on the shape of concaved from the hexagon. Six types of shape of model was tested. The shape of model considered with the angle of concavity and the circumference of disc. The angle of concave was investigated as 15, 30, 45 degrees. The motion of model was free-fall in a water tank. The tank filled the water. The model motion was taken by using the high speed camera. The image analysis was carried out to investigate the velocity and acceleration of model. The drag coefficient was obtained with the force balance during the motion. The results show that the drag coefficient increase with the increase of the angle of concavity in case of constant area of model. The results with the constant circumference of model show that the drag coefficient increases with the decrease of the angle of concavity of model. The drag coefficient converged in the terminal velocity.

Aerodynamic performance of Thin-trailing-edge airfoil with and without exposed rib structure at Reynolds number 23,000 are evaluated using implicit large-eddy simulation. Both the wing with and without rib structure showed preferable performance compared to that of Ishii airfoil, which is known as well performing airfoil at low Reynolds number. Also, it is found that the rib structure degrades the performance at low and middle angle of attacks, while the rib structure is designed to minimize performance degradation at 3 degrees of angle of attack. Moreover, the results imply that the rib structure delays stall, and slipping angle of freestream doesn’t affect much to the characteristics of the wing.

The characteristics of subsonic nozzles with Fluidic Thrust Vectoring (FTV) were investigated experimentally. FTV nozzles having different cross section area of throat part [Nozzle A,B,C] were designed and built in order to investigate the effect of nozzle contraction ratio and swirl flow on thrust vectoring effectiveness. Deflection angle, pitching moment and thrust of aircraft with the FTV nozzles were obtained though the results of the experiments.

This paper describes deposition phenomenon which is one of the serious problems of gas turbines. Various numerical studies have been performed on the deposition behavior of single metal droplet, while the deposition behavior of multiple metal droplets has not sufficiently been studied by numerical simulations. In the present study, for the numerical simulation, the particle-based method was used to reproduce the spreading and solidification of the droplets impinging on the iso-thermal and non iso-thermal substrates. The calculation target was two molten tin droplets with the diameter of 2.2 mm, where the second droplet was sequentially dropped to the substrate with the center distance offsets of 3 and 4 mm. Particles were arranged on the surface of the substrate, and the temperature change was calculated by performing the grid-based computation inside the substrate. The numerical results were compared with the experimental and computed results. The results showed that the spreading shape of the second metal droplet is strongly affected by the deposit of the first droplet. Moreover, the spreading of the droplets become similar to the experiment in comparison to the isothermal case. In addition, the transient tendency of the spread factor shows reasonable agreement with the experiment by computing the temperature change in the substrate.

The rotational behavior of a lifting capsule was investigated using 3DOF free rotational apparatus in a wind tunnel. The effect of roughness was investigated, given by glass beads and by hemispherical pattern made by 3D printer. The pitch and roll behaviors were compared and the effect of the surface roughness was investigated in a flow of Mach 0.3. The roughness of one percent of capsule diameter completely suppressed the rolling motion, which was peculiar to the capsule with smooth surface. It also enhances the damping characteristics in pitch oscillation.

Two-phase flow loop cooling system is required for increasing heat transfer rate, heat transfer distance, and cooling heat flux in thermal control of space structures. It is necessary for the design of the system to clarify heat transfer and flow characteristics of gas-liquid two-phase flows in boiling, condensation, and adiabatic flows under microgravity. In order to realize one-component gas-liquid two-phase flows under stable microgravity condition, two-phase flow experiments had been carried out as a JAXA project named TPF experiments in Japanese Experimental Module “KIBO” of International Space Station (ISS). In this report, the outline of TPF experiments is introduced with some experimental results of adiabatic gas-liquid two-phase flow behaviors just at the downstream of a copper heating tube.

Extending the storage period for cryogenic propellant is necessary for future space exploration such as Mars transportation. In a space mission, the heat entering from solar induces evaporation of cryogenic propellant and generates the boil-off gas (BOG) from propellant. The BOG causes self-pressurizations of the storage and shorten its storage period. Therefore, a pressure regulation system is necessary for extending the storage period. The Thermodynamic vent system (TVS) is the system which regulates pressure of the storage tank by reducing BOG with active thermal management. In this study, we did experiments of jet mixing using liquid nitrogen (LN₂) against the LN2 self-pressurized tank in ground gravity environment to verify pressure regulating function by jet mixing which is a component of TVS. As a result of the tests, jet mixing reduced boil-off rate by about 90 %. On the other hand, jet mixing with a smaller supply flow rate could reduce boil-off rate only slightly.

Using ultrasound pulse echography, the air flow rate is measured for air-water two-phase flow in a pipe that spans multiple flow regimes. The air-water interface obtained by the signal is classified into small bubbles and large bubble by the time that passed from ultrasound measurement line, and air flow rate was measured using different methods for each bubble conditions. Measurement accuracy is validated using the time fluctuation of the injected air flow rate. The results show that proposed technique has possibility to measure time fluctuation of the air flow rate in air-water two-phase flow in a pipe from outside even if flow regimes changes by time.

Gas–liquid two-phase flow under tilted plates is experimentally studied to investigate effects of the slope condition which occupies a large area of the hull for BDR (Bubbly Drag Reduction). Bubbles were injected in front of a 0.4-m model ship with different tilted angle and the ship was towed in a 5-m towing tank. The negative and positive angles with the moving direction of model were selected as slope conditions, and the flat condition is also adopted for the comparison with the slope conditions. The boundary layer which is changed by slope conditions was visualized by a high-speed camera, and the bubble behaviors were observed as well. Advection velocity of bubble is increased in the negative slope condition and decreased in the positive slope condition by the buoyancy effect. The velocity of small bubbles, however, are mainly affected by liquid phase flow due to weakening of buoyancy effect. Finally, we suggested an empirical equation predicting the advection velocity of bubble in the slope conditions.

Total drag of ship is dominantly governed by frictional drag. Bubbly drag reduction (BDR) is expected as a major solution to reduce the friction as bubbles alter the turbulent boundary layer structure. We conducted a feasibility study of BDR by means of repetitive bubble injection aiming further improvement of drag reduction performance using a 36-m long flat model ship. By measuring local wall shear stresses as a function of distance from the bubble injection point at a speed of 7 to 10 m/s, we found wavy fluctuation of the shear stress due to void waves passed by the bottom plane.

An image reconstruction method for rotating machinery has been developed based on the measurement of linear sensor wireless electrical resistance tomography (LS-WERT). It can measure the real-time particle deposition thickness in centrifugal fields. The linear sensor is composed of eight electrodes attached as a single line in the inner wall of the centrifuge and connected to WERT which transmit the measured resistance to the processing PC. The measurement of LS-WERT works effectively inside the boundary of the effective sensing planar-area. In order to evaluate the fluid dynamics in centrifugal field, a coupling of SPH-DEM simulation based on Lagrangian method was conducted. The coupling confirms the interaction between the liquid and particle position under different rotational speeds. This position is important for evaluating the electrical measurement based on the FEM mesh conductivity of EIT method. According to the fluid dynamics in centrifugal field, the higher rotational velocity gives greater centrifugal forces causing an upward parabolic interfaces. The measured resistance from LS-WERT indicates particle detection which was pushed against the wall in different heights. Finally, the image reconstruction based on Artificial Neural Network (ANN) method can be specified without setting a threshold value and gives a good agreement with the numerical simulation.

To evaluate the water-accumulation phenomena and electrochemical characteristics in an operating polymer electrolyte fuel cell (PEFC), simultaneous measurements of water distribution in the through-plane direction and the electrical impedance were carried out by using a neutron radiography and electro-chemical impedance spectroscopy. The water distributions were obtained every 60 sec after the power generation, and the two-dimensional water distributions were compared with the proton exchange membrane (PEM) and the reaction resistances. Change in conditions of power generation, geometry of the gas channel and with or without micro porous layer (MPL) affected the water accumulation in the PEFC. The PEM resistance decreased with increasing the water saturation in the membrane at the beginning of the power generation. Reaction resistance increased with the liquid water in the gas diffusion layer (GDL) and the gas channels. Therefore, rapid increases of the reaction resistance were confirmed at higher current density. We also evaluated the correlation between ion conductivity and membrane resistance. Ion conductivity increased with water content in the PEM. However, the membrane resistance was less affected by the water contents at low range of the water content in comparison to the Springer’s model.

Kettle type heat exchanger with horizontal tube bundle have been widely used as an evaporator in geothermal binary power plants. It is known that bubbles movement agitates the liquid phase, resulting in increased heat transfer in the nucleate boiling region of two-phase flows. Hence, clarification of the relation between bubbles movement and heat transfer is important for optimizing the heat exchanger. This study was conducted with the objective of clarifying the bubbles movement and heat transfer around tubes in two-phase flows under adiabatic conditions. In this study, air-water two-phase flow experiments were carried out using a vertical duct test sections with inner dimensions of 90 × 90 mm². The tube bundle was staggered containing four columns and eight rows. The tube diameter was 18 mm and the pitch was 22.5 mm. The working fluids were air and water, and flow observation and measurements of local heat transfer around a tube were conducted. Fluctuation of heat transfer was caused due to large bubbles movement. It was found that the heat transfer at top of the tube was more influenced by movement of the large bubbles. Furthermore, the instantaneous heat transfer in intermittent flow was higher than that in bubbly flow. Therefore, it is considered that the flow fluctuation caused by large bubbles plays an important role to enhance the heat transfer.

Development of high efficiency heat exchangers has been promoted for effective utilization of heat energy. This study focuses on boiling two-phase flow behaviors in a cross-flow type parallel mini-channel heat exchanger made by diffusion bonding. Phase distributions of vertically upward flows were evaluated based on the results of void fraction distribution measured by neutron radiography. The effect of the configuration of refrigerant channel was considered. Three types of refrigerant channel, such as the straight type, perforated rib type and offset rib type, were examined using R134a as the refrigerant. The refrigerant was supplied to the test section as subcooled liquid with the mass flux of 75 to 500 kg/(m²s). Incoming subcooled liquid was distributed into 28 parallel channels with the hydraulic diameter of 1.04 mm, and heated by fluorocarbon FC3283. The heating medium, FC3283, was supplied with the mass flux in the range of 460 to 2947 kg/(m²s) and at the inlet temperature of 49.9 to 70.6 °C. As the results, it was shown that void fraction close to the inlet of the heating medium was relatively higher due to the larger temperature difference. An improvement effect could be obtained by using the perforated type with interrupted ribs, because the onset of nucleate boiling was promoted at the perforated part of the rib.

To achieve higher density Hard Disk Drive (HDD), Helium–sealed HDD has been used recently in the aim of decreasing the flow–induced vibration (FIV) of the disks. Previous researches have been conducted at higher Reynolds numbers, at which the flow between the disks is fully turbulent as in commercial HDDs with air. In the Helium-sealed HDDs, on the other hand, the Reynolds number is lower by one order magnitude due to small density of Helium, and may therefore be in the transitional range between laminar and turbulent regimes. In this report, we experimentally investigate the flow between multiple co-rotating disks in a cylindrical enclosure, at transitional Reynolds numbers, as a simplified model of the flow in Helium-sealed HDDs. The measurements of pressure fluctuation were carried out by a condenser microphone, and the statistics (Root-Mean-Square, Skewness, Flatness) of pressure fluctuation were calculated. Wavelet analysis was further applied to experimental results to study the intermittency in the spectral features of the flow. It was observed that the flatness of the fluctuating pressure increased at low disk rotational speeds corresponding to the typical disk Reynolds numbers of the Helium-sealed HDDs. The wavelet analysis also showed that at such moderate disk rotational speeds the pressure fluctuation at relatively high frequencies appear intermittently. These results indicate that the flow between the co-rotating disks exhibits intermittent structures at the transitional disk Reynolds numbers.

Influence of low-frequency fluctuation of aerodynamic force on vehicle stability has been attracting attention in recent years. In this paper, detached-eddy-simulation was conducted on a one-fifth scale vehicle model, of which the original vehicle showed different performance in driver assessment by adding a tiny part. As a result, the modified model decreased low-frequency fluctuation in the rear and floor. Also, cross correlation between aerodynamic lift force acting on the rear axle and pressure at the side of rear window was decreased. In order to investigate characteristic fluctuation pattern, proper orthogonal decomposition (POD) was applied to surface pressure of rear window and velocity in wake region individually. The surface pressure of rear window had characteristic modes with the fluctuation which are corresponded with aerodynamics force. The velocity in wake region had two characteristic modes with low-frequency fluctuation. Reconstructed flow field from a summation of these two modes showed intermittent flows from both side of wake to center. Though a vehicle model with the tiny parts also showed the low-frequency fluctuation of two similar modes, their intensity was decreased. Finally, the difference was associated with the fluctuation of aerodynamic force.

It has been confirmed that tapered cylinders have the effect of reducing radiated aerodynamic noise compared to square cylinders. In this paper, the relationship between the static pressure fluctuation of the wake and the characteristics of the distant field sound was clarified by the simultaneous measurement of the static pressure fluctuation of the tapered cylindrical wake and the distant field sound using a conical tip type static pressure tube probe. We also investigated the surface pressure of the tapered cylinder. The Reynolds number based on the mainstream velocity and the diameter of the cylinder in the midspan is 2.65 × 104. It was confirmed that in the tapered cylinder, the peak value of the aeolian sound observed in the right cylinder was significantly reduced and the peaks were dispersed, and the broadband components before and after that were also reduced. In addition, it is highly possible that there is a flow structure that contributes to noise corresponding to each frequency on the lower end side of TC1 and on the upper end side and lower end side of TC2. Furthermore, the surface pressure fluctuation of the tapered cylinder became smaller as the taper ratio increased, and the peak became backward.

Small axial fans are used for cooling electronic devices, and have been often installed in a casing with slits to improve aerodynamic performance in recent years. However, when the fan is actually installed in a product, the inflow region may be limited to narrow space due to other components of the product. In order to clarify the effects of the upstream duct width on the aerodynamic performance and aeroacoustic noise of the axial fan in a casing with slits, the flow and sound around the fan installed in a duct were directly predicted based on the compressible Navier-Stokes equations. The computational methods were validated by comparing the predicted pressure rise by the fan and the sound pressure spectrum with those measured. At the flow rate near the design condition, both the predicted and measured results showed that the pressure rise by the fan deteriorates for H/D = 2.0 and is higher for H/D = 1.0 compared with H/D = 4.0. Narrowing the duct width from H/D = 4.0 to H/D = 2.0 resulted in a 5% decrease in the efficiency defined by the ratio of the pneumatic power to shaft power estimated from the integration of the surface pressure on the fan blades. It is because the outflow of pressurized air through the downstream part of the slit increases for H/D = 2.0 comparing with H/D = 4.0. Both the computational and experimental results showed the sound pressure level in a wide frequency range became larger for the narrower duct width. The vortices caused by the blade tip vortex of a blade were found to be distributed in a larger region between the blades. The interference of the vortices with the pressure surface of the adjacent blade leads to the intensification of the power of pressure fluctuations on the pressure surface particularly in the low frequency range.

Aerodynamic noise generated from the bogie section is one of main sources when high speed trains run above 300km/h. Therefore, it is important to reduce the aerodynamic bogie noise appropriately. In this paper, the relationship between the flow field around the bogie and the aerodynamic bogie noise are investigated. To examine the relationship, a wind tunnel test was carried out by using a two-dimensional microphone array and Pitot tube rake. Two countermeasures to control flow at the bogie, i.e. deflector and concaved bottom section, were developed. It is found that the flow speed around the bogie was reduced by these countermeasures. And, it is found that the aerodynamic bogie noise was properly reduced in proportion to the reduction in flow speed.

The Venturi Scrubber is one of the most effective nozzles for the wet-scrubber type Filtered Containment Venting System. The advantage of a Venturi Scrubber nozzle is that it is capable to remove dust particles and radioactive gas materials due to contact with the liquid droplets which are atomized into the throat of the nozzle. Therefore, the efficiency of the venturi scrubber also depends on the atomized water flow rate. In this study, the effects of the double-stage venturi on the on the atomized water flow rate was investigated at several conditions of the air injected flow rate. Two configurations of the venturi scrubber nozzle were used. The velocity of water at the gaps of the nozzle was measured using Ultrasonic Velocity Profiler method. The results showed that the water velocity was decreased as increase of the air injection flow rate.

Accurate flow rate measurements are required in many industrial plants. The flow rate for feedwater is one of the important parameters in many power plants. Therefore, evaluation of existing flowmeters is sometimes required. One of the effective solutions to measure the flow rates in existing pipes is to use clamp-on ultrasonic flowmeters that the ultrasonic sensors are installed at designated points external to the piping system. To improve the measurement accuracy, parallel multiple measuring lines have been generally employed for in line type ultrasonic flowmeters. However, it is difficult to set the sensors on parallel for the clamp-on type. In this study, we focused on an ultrasonic tomography method that reconstructs the flow velocity distribution using multiple measurement lines. For the tomography, ultrasonic should be emitted with wide-divergence angle and the signal is received at several sensors. To develop the clamp-on ultrasonic tomography method, wide-divergence angle sensors were manufactured. The transit-time difference between the downstream and upstream sensors was evaluated. It was shown that the transit-time difference between the sensors in diametrical direction changed in proportional to the flow rate. Therefore, the wide-divergence angle sensor was found to be used for flow rate measurements using the tomography method.

Ultrasonic tomography (UT) is a powerful tool for measuring two-phase flow phenomena because it can be applied to opaque fluids and is easy to use. However, its temporal resolution is not as high as those of other methods, such as capacitance or X-ray tomography. Improving the temporal resolution of UT is essential for evaluating time-dependent phenomena. Reduction in the number of transducers is a key requirement for improving the temporal resolution. In this study, a wide 110° divergence angle transducer with a vertical height of measuring volume of approximately 4 mm was developed for high-speed tomography. The transducer provides an echo signal with a good signal-to-noise ratio. A reflection-mode UT system was developed using eight transducers to measure the two-phase flow in a container with an inner diameter of 50 mm. Because the pulse transmission interval was set at 0.125 μs, a temporal resolution of 1 ms was achieved. The time resolution was achieved at 1 ms with frame rate of 500 FPS. We reconstructed the bubble interface by back-projecting signal intensity distribution on the elliptical arc with focal points at the transmitter and receiver positions. To reduce the artifacts in the pack projected distributions, a weight distribution function based on the reflected signal was introduced. The system was applied for measuring bubbly flows in a container for evaluation of the CT reconstruction. It was shown that the 2-D void distributions were clearly obtained and the pseudo-3D images were useful for evaluating the bubble distributions.

The emulsification method is not only one of the potentially effective techniques to reduce fossil fuel consumption but also exhaust emission from diesel engines. Water-in-Oil (W/O) emulsified fuel is reported to reduce the emissions of NOx, SOx, CO and particulate matter (PM) caused by a decrease in combustion temperature and a micro explosion in combustion. However, the emulsified fuel shows non-Newtonian properties called pseudoplastic flow as water content ratio increases. Since a viscosity of pseudoplastic flow decreases with increasing shear rate, the W/O emulsified fuel causes clogging of fuel injector, decrease of combustion efficiency due to deterioration of fuel spray in high water content ratio. It is important to know a flow state of the emulsified fuel in mixing conditions. In this study, we evaluated W/O emulsified fuels using ultrasonic measurement, produced 10 %, 20 %, 30 % water-vegetable oil emulsion at 300-800 rpm with a Taylor-Couette flow reactor. We measured velocity profiles and attenuation of echo at every 100 rpm utilizing the ultrasonic Doppler method and echo intensity measurement. Then, As a result, transitions of the velocity profiles and the echo attenuation were different in each water content ratio.

The development of efficient recovery methods for valuable metals and radioactive nuclides discharged in the nuclear fuel cycle reprocessing process is required. Therefore, we propose a method using the Taylor Vortex Flow. It is expected that the characteristics of the Taylor vortex flow device will allow for uniform and mild absorption and separation. However, there is instability of the flow field in low aspect ratio Taylor vortex flows. Conversely, it is possible to control the flow field by external influences. In addition, magnetized absorption materials are expected to promote the mixing and stirring action and to enable the development of simple recovery systems. Therefore, it is thought that the stirring efficiency may be improved in response to the application of an external magnetic field by making the absorption material magnetic. It is also expected to develop a simple recovery method using magnets. In this study, the Taylor vortex flow in the case of mixing magnetic particles into the working fluid was measured by UVP as a fundamental study. As a result, the applicability of magnetic particles to flow field measurement using UVP was confirmed. It is possible to measure fluid velocity using only magnetic particles, the flow field measurement of the magnetic absorption material alone can be performed in the development of absorption and separation systems, which will enable more accurate performance evaluation.

A new measurement system is proposed in this study to detect the defect inside pipeline through both the UT inspection of pipe wall and the flow velocity profile derived by UVP method. With this new measurement system, the beginning and the height of the defect would be detected, it would also possible to evaluate the size of crack if enough data are collected. This is a fundamental study of the combination of two techniques, since the capability of UT and UVP are both limited, two sensors are put into a wedge to collect both data from both signals, it is expected to develop an integrated sensor to conduct the measurement. In this paper, a fundamental study on simultaneous measurement of flow and pipe defects using pulse ultrasonic wave is discussed. The validity of a constructed system for pipe defect detection and flow measurement, which utilizes ultrasonic signals using simulated defective pipe is reported.

This paper presents the development of the Ultrasonic Velocity Profiler (UVP) method to obtain the two-dimensional (2D) velocity vector profile of bubble and liquid on the bubbly flow and apply in the sub-cooled boiling condition. To accomplish the objective, multiple transducers and developed signal processing are applied to the UVP system to reconstruct a 2D velocity vector profile of both phases simultaneously. Besides, the temperature effect on the ultrasonic signal influencing the classification of both phases velocity data has been analyzed and utilized to improve the measurement processing. The ability of the developed UVP was demonstrated in the sub-cooled boiling bubbly flow where the 2D velocity vector profile of bubble and liquid was obtained separately and reasonably