Pantographs, crucial for electric trains to collect high voltage AC from overhead wires, vary in geometry. The Indian Railway Section uses high-rise overhead equipment (OHE) lines for freight trains with double-stack containers. These elevated OHEs, 36% higher than standard, pose unique aerodynamic challenges. Prior research highlights the pantograph's role in aerodynamics, focusing on uplift generation, dynamic interactions, and stability in pantograph-catenary systems. Full-scale train tests are difficult, making numerical simulations more efficient and cost-effective. Adjusting static upthrust force for pantograph improves the current collection but raises concerns about contact strip wear and entanglements. This study aims to develop a method to investigate the aerodynamic behavior of high-rise pantographs using the immersed boundary method in a High-Performance Computing (HPC) environment.

Ice accretion on aircraft surfaces occurs when supercooled water droplets impact the surface, leading to the formation of ice layers that disrupt airflow, reduce aerodynamic performance, and cause significant safety risks. Thus, accurate prediction of ice accretion is crucial during the aircraft design phase. Supercooled large droplets (SLDs) exhibit splashing and bouncing upon impact due to their larger inertia. At relatively higher ambient temperatures, a thin water film may form on the surface and flow backward due to airflow-induced shear forces, resulting in runback phenomena. Therefore, accurately predicting the surface state (ice or liquid film) is essential to consider the interaction between the flowing water film and impinging droplets. In this study, numerical simulations of SLD icing on a NACA0012 airfoil were conducted. The flow field was computed using the Eulerian approach with the finite difference method (FDM), while the droplet motion was simulated with the Lagrangian approach. Considering the surface state, the simulation accounted for characteristic behaviors of SLD icing such as splash, bounce, and breakup. The shallow water equation (SWE) was introduced to model the water film behavior and simulate runback phenomena. The interaction between droplets and the flowing water film resulted in changes to the actual droplet impact behavior. Additionally, the movement of the water film formed on the surface reproduced complex ice shapes, such as horn shapes.

Ice crystal icing is a phenomenon that occurs in warm tropical regions and causes engine power loss. In this study, we perform numerical simulations of ice particle impact on a wall with liquid water film at multiple impact angles using the particle method to improve the prediction accuracy of ice crystal icing. In the numerical simulations, the particle method was used, which can easily reproduce large deformations at the interface. The MPS method and the E-MPS method were used for ice particles and liquid film particles, respectively, and each phase interacts through the surface tension, viscous forces, and pressure. The numerical simulations reproduced the attenuation of the tangential coefficient of repulsion due to the presence or absence of a liquid film and showed that the coefficient of repulsion decreased at a smaller angle of attack. Under high-speed conditions, the breakup behavior of ice particles was observed to change with varying the impact angle.

Ice crystal icing is a phenomenon where ice particles are ingested into a jet engine, potentially forming a layer of ice in the compressor. It can lead to engine power loss, though the mechanisms behind ice crystal icing are not yet fully understood. Therefore, modeling of ice crystal icing remains an urgent issue. Recent experiments on ice crystal icing have revealed phenomena such as sticking, bouncing, and erosion of ice particles under various conditions. While ice crystal icing models incorporating the effects of sticking and bouncing have been developed in recent years, there are only a limited number of models that account for ice erosion. This study introduces a novel ice crystal icing model that incorporates an ice erosion. The icing simulation consists of four steps: flow field computation, ice particle trajectory computation, thermodynamic computation, and grid modification. The proposed ice erosion model was derived from a semi-empirical model employed in predicting sand erosion based on classic solid/solid collision theory and was integrated into the thermodynamic model. The parameters for this semi-empirical model were selected based on the impacts of ice particles on the ice layer. Numerical simulations of ice crystal icing were conducted under various conditions using the ice erosion model. The results revealed a significant discrepancy in the predicted icing shape depending on the presence or absence of the erosion model. In addition, the model was also validated through comparison with experimental data.

Concentration polarization occurs in all membrane-based technologies and is a major factor in reducing the efficiency of desalination, concentration-based power generation, and other membrane-based technologies. Therefore, we considered that changing the surface geometry of the permeation membrane would change the flow and thus affect the concentration polarization. In this study, we simulated forward osmosis using the Lattice Boltzmann Method (LBM) to investigate the effect of the surface geometry of the permeation membrane on the amount of permeation. The results showed the following. The larger the protrusion, the more permeation volume compared to the flat membrane. The concentration is lower upstream and downstream the protruding membrane and higher on the protrusions than on the flat membrane. The concentration polarization layer on the protrusions is thinner than that on the flat membrane.

Ice accretion on an aircraft occurs when supercooled droplets in a cloud impinge on a body. Aircraft icing threatens navigation safety as icing on a wing deteriorates aerodynamic performance. Although it is required to predict icing accurately, estimating ice accretion is challenging due to its multi-physics nature. In addition, under supercooled large droplet (SLD) conditions, where the droplets’ diameter is over 40 μm, the behavior of impinging droplets becomes more complex. In this study, numerical simulation for SLD icing using coupling scheme of grid- and particle-based methods were conducted. The numerical scheme for heat transfer treatment in the particle-based method was improved to reproduce the solidification process of droplets. In addition, highly resolving simulation was realized by applying a computational cost reduction method. As a result, the ice shape apart from the leading edge backward was reproduced with higher resolution than in our previous study. Furthermore, the catalyst of the unique ice shape in SLD icing (i.e. feather shape) was observed. The present simulation scheme will provide a more useful prediction for SLD icing in the designing phase of an aircraft.

When minute supercooled liquid water droplets or ice impact on a cold object surface in a low-temperature environment, they freeze at the impact surface. This is known as icing phenomena. In aircraft, attention has mainly focused on icing on the aircraft fuselage, but icing also occurs in compressor of jet engines. When icing occurs, not only is the performance of the jet engine decreased, but the detached ice can damage the compressor cascades. Therefore, the icing of compressor cascades is an important issue. In this study, prior to examining the icing on the compressor cascades, we examined the icing on a single blade of compressor. The ice shape and mass to the blades were investigated with flow velocity and attack angle as parameters.

One of the important functions of a mixer is to uniformly mix powders and liquids. In this study, a 3D motion mixer with a sealed vessel without stirring blades was used. However, the flow state of powders and liquids in a sealed vessel is unknown, and it is generally necessary to open the vessel to examine the mixing state to evaluate it. Therefore, a transparent container containing silica sand and fluorescent particles was placed in the mixer and an experiment was conducted. In previous studies, the results of the remaining conditions were predicted by producing some conditions for the powder filling rate and container rotation speed. Therefore, we demand to more clearly determine the time required to reach dispersion for each condition. As a result, the time required for dispersion under different conditions was more clearly defined for the powder filling rate and container rotation speed than the previous results.

Mechanical seals are used to control leakage in rotating machinery, such as fuel pump or power generating pump. Those mechanical seals consist of two rings, a stationary ring and the rotating ring. The stationary ring is fixed to the housing around the shaft hole and the rotating ring is fixed to a shaft which rotates with it. While the machineries are in operation, two rings keep micron scaled gap by generating the hydrodynamic pressure between the sliding surfaces. Furthermore, it has been found that spiral grooves with a depth of a few microns on the stationary ring surface can form the sufficient hydrodynamic fluid film on the lubrication area. However, CFD-based predictions of the flow field in the lubricating area inside mechanical seals with surface textures have not been fully developed. In this study, we tried to understand the flow field of a few microns of the lubrication area with spiral grooves inside the mechanical seal in CFD analysis.

A top-loading washing machines use a pulsator to raise the pressure and spray water with detergent solution from the top of the clothes in a shower-like pattern, and achieve high washing power by changing the clothes and rubbing the clothes with the pulsator movement. This study used the moving particle simulation to predict the shower flow rate and visualize the flow in the tub by the pulsator. The shower flow rate in the analysis and the relative difference in flow rate due to different pulsator geometries generally agreed with the experimental values. The visualization results of the flow velocity distribution above the pulsator showed that the rotational axial and circumferential velocities varied with time, confirming the characteristics of the flow field depending on the geometry of the pulsators. It was confirmed that the developed pulsator has a flow field that moves clothing in the radial direction of the pulsator.

This study aimed to elucidate the mechanism of sudden acceleration of a sphere settling in a wormlike micellar solution. To this end, high-time-resolution birefringence observations were performed using an event camera. In the experiment, a stainless steel sphere with a diameter of 6.35 mm was permitted to settle in a stationary aqueous solution of CTAB/NaSal (30 mM, counterion molar ratio 4). The visualization of shear waves was achieved using the crossed polarizers method, which was then observed with an event camera. The results revealed significant differences between two successive rapid accelerations within a short time interval. Immediately following the initial rapid acceleration, birefringence was observed to be temporarily enhanced directly behind the sphere. Strong shear waves were generated from behind the sphere during the subsequent rapid acceleration. These observations are partially consistent with the previously reported rubber-band-cutting model and allow for the estimation of the cutting position. Using an event camera enabled the detailed observation of high-speed phenomena that were previously difficult to capture.

Most of the studies using ultrafine bubbles (UFB) use water as the solvent. In this study, we focused on solvents other than water and investigated the effects of ultrafine bubble mixing and its usefulness experimentally by examining changes in the physical properties of liquids when ultrafine bubbles are generated directly. Water and water-soluble coolant liquid were also used in this experiment as a comparison.

In this study, we have investigated the influenced of the change in stress amplitude and flow properties of polyethylene glycol (PEG) solution as a suspending medium for Cellulose nanofiber (CNF) suspension by using large amplitude oscillatory shear (LAOS) measurement. The experiments were conducted with a stress-controlled rheometer, the frequency was fixed and the stress amplitude was varied. The applied stresses were entered at 6.0, 15, 18 Pa, and the strains were set to 2.0 8.2 24. The Lissajous curves obtained by LAOS measurement were evaluated. The effect of suspension ratio and stress of CNF suspension on LAOS measurement was investigated. the anomalous responses of strain were obtained in CNF suspension. In particular, the approximate shape of the parallelogram-like ellipse is shown for strains 2.0 and 8.2. At a strain of 24, the shape of the ellipse approached a circular shape, confirming the increased hydrodynamic effect. The above results show that the properties of the CNF suspension changed depending on the applied stress.

To mitigate the impact of low-concentration methane with a high global warming potential and that is difficult to recycle, the use of plasma actuators (PA) has been explored. This is because PA can generate airflow without moving parts as well as oxidize substances in the air. To achieve high energy efficiency in the treatment, PA should be used in combination with catalysts at a high dielectric temperature. Therefore, the purpose of this study is to investigate the effect of the surface temperature of the dielectric on the performance of PA. A heat-resistant PA capable of withstanding high temperatures, made of alumina dielectric, was created for this study. As a result, it was confirmed that the higher the surface temperature, the faster the flow velocity and the wider the acceleration region. Observation of discharge images using an ICCD camera also showed that area of negative polarity discharge expanded as the temperature increased.

Dielectric Barrier Discharge Plasma Actuator (DBD-PA) is a flow control device consisting of a single dielectric sandwiched between an AC and a ground electrode. In this study, we focus on DBD-PA having two opposing AC electrodes (Facing-PA) which is expected as vortex generator with active controllability. It was reported that the discharge in Facing-PA was enhanced compared to the conventional DBD-PA, and its mechanism was considered to be electric field enhancement due to residual charge on the dielectric surface, but there are no experimental results supporting this hypothesis. In this study, for clarifying the discharge enhancement mechanism of Facing-PA, we experimentally investigate the dielectric surface charging. We conduct the imaging of discharge photoemission and the Pockels measurement of surface charging. For this purpose, the BGO (Pockels crystal) is adopted as the dielectric. As a result, an increase in residual surface charge due to the discharge extending from the opposing electrode is confirmed, but the discharge enhancement effect could not be confirmed, and it imply the residual charge has small impact on the discharge.

To investigate the effects of ultraviolet (UV) light on the electric characteristics of plasma actuators, we measured the discharge current of surface DBD reactors while irradiating the dielectric surface with 269 nm UV light. The DBD reactors used were two types: a coplanar DBD reactor and a typical single plasma actuator. The current spikes of coplanar discharge were reduced and may result from two effects: atoms created by UV photodissociation near the surface and the electrons attached to them (Joshi effect); surface electrons emitted by continuous UV irradiation, preventing simultaneous filament formation, called collective effect. On the other hand, current spikes observed in the plasma actuator operation in the positive-going phase slightly increased at lower voltage. It suggests that microdischarge behavior under the UV irradiation is determined by the superposition of Joshi effect and suppressed collective effect.

In this experiment, two DBD-PAs and a flame retention device were used in a coaxial double-tube nozzle with pseudo-biogas fed from the inner nozzle and air from the outer nozzle to suppress ignition vibration of pseudo-biogas and contribute to carbon neutrality. Experimental methods and visualization of the jet flow were used. As a result, no significant control could be confirmed at present. In the future, we would like to increase the flow velocity to confirm the control of the jet flow.

Large-eddy simulations on pre-stall airfoil-flow control using spanwise type plasma actuator (SP-PA) and vortex-generator type plasma actuator (VG-PA) have been conducted. These simulations were carried out with a Reynolds number of 63,000 using a NACA0015 airfoil, set at an angle of attack of 4°. In this paper, we focus on examining the effect of the PA's installation length, installation method, and driving method on the control effectiveness. The simulation results show that using VG-PA promotes the transition to turbulence, which led to a reduction of the laminar separation bubble region and consequently lowered pressure drag. Although there is an observed increase in friction drag, the overall drag is reduced. This reduction in total drag leads to an improvement of lift-to-drag ratio.

A dielectric barrier discharge plasma actuator (PA) is a flow control device that can suppress flow separations. Previous studies have shown that burst actuation is especially effective for this purpose. An experimental study applied deep reinforcement learning (DRL) to the flow separation control and conducted feedback control to dynamically determine the non-dimensional burst frequency F⁺, according to the flow field. In this study, we make a framework coupling the DRL and large-eddy simulations whose fidelity reproduces the unsteady flow features to investigate the detailed flow fields controlled by PA with DRL. The framework found the optimal burst frequency clarified by the previous study at the angle of attack, 12 degrees. The suppression of flow separation was not completely achieved, but the results showed that the DRL models temporarily improved the lift coefficient, and a characteristic burst drive appeared at the angle of attack of 15 degrees.

Among various driving forces of longitudinal ventilation flow, we know “natural air flow”. This is related to pressure difference between both portals caused by meteolorogical conditions, but it seems that the phenomena is sometimes not understood appropriately. The author describes definition of this phenomena firstly. Consideration is done on what happens due to differene in altitude of both portals, and explains the importance of measurement of natural air flow in tunnels before public service. Discussion is led also on the measurement of pressure difference in tunnel, where bouyancy effect can affect accuracy.

In previous reports, simulations are performed for a car tunnel fire using FDS+EVAC to estimate the amount of carbon monoxide inhaled by stationary people placed in the tunnel. The results shows that people near the side walls inhaled more carbon monoxide than people in the center. Since evacuees generally walk near the side walls and emergency exits are installed on the side walls, it is necessary to consider safety measures. Therefore, this report carefully observed the simulation data and investigated how carbon monoxide moves during a tunnel fire. In this report, the tunnel fire simulation is conducted using the same tunnel shape and fire source conditions as in previous reports, but the latest version of FDS6.9.1 is employed. In addition, in order to investigate the horizontal carbon monoxide concentration, the simulation conditions are set to output the carbon monoxide concentration distribution at different height cross sections. At heights of 1.0 m, 1.5 m, and 2.0 m, these are shown that the carbon monoxide concentration near the sidewall is higher than that near the centerline in the uphill direction near the fire source, but then there is an area where the concentration near the centerline is higher. Further to the uphill direction, the difference in concentration becomes smaller, but the concentration near the sidewall is again higher near the tunnel exit.

In this study, we developed a new design for the turnbuckle used in the suspension system of Jet Fans. The traditional turnbuckle required individual production to match the shape of the Jet Fan and the tunnel, posing significant challenges in terms of production time and cost. The newly developed turnbuckle, with its simple structure, shortens the production time and improves versatility by allowing adjustments to fit the diameter and hanging bracket position of the Jet Fan. It was confirmed that the strength and durability are equivalent to the traditional turnbuckle. The production cost is currently similar, but a future reduction is expected due to its universal structure.

In the tunnels of the Metropolitan Expressway, there are 217 jet fans installed, necessitating lane restrictions for many days for inspection purposes. Therefore, our aim was to conduct measurements of jet fan motion to understand structural anomalies and achieve continuous monitoring. In our previous report, we explained that frequency analysis and trajectory analysis using a measurement 3-axis accelerometer are effective for measuring jet fan motion. In this report, we developed a MEMS sensor integrated with low-cost components based on these two analysis methods. We compared the measurement results of the MEMS sensor with those of the measurement 3-axis accelerometer and found them to be equivalent. This verification that the MEMS sensor is effective for measuring jet fan motion.

The Kan-etsu Tunnel is the longest mountain tunnel in Japan, with a length of approximately 11 km, and longitudinal ventilation is operated using fans installed in two underground ventilation stations and one precipitator room on each of the outbound and inbound tunnel. These fans have a variable rotor blade angle in consideration of air volume adjustment and the effect on the electric motor. In recent years, there have been occasional cases which it has become difficult to adjust the blade angle of the fans installed in the precipitator room due to rust caused by antifreeze sprayed in winter. Therefore, it was required to consider upgrading the system to one with a fixed blade angle and variable motor speed controlled by an inverter. This report describes the results of tests conducted during the retrofit and the operating status after the retrofit.

In high-speed railways, the strength of the infrastructure and car bodies is highly dependent on the pressure fluctuations generated by trains passing through tunnels. Numerous experimental studies have been conducted to simulate these pressure fluctuations. Although axisymmetric 1 / 100 scale moving model rigs are useful, a more in-depth investigation of the three-dimensional effects is required to increase train speeds. In this study, a large-scale moving model rig was developed. Six pairs of rotating wheels were used to accelerate the carriage. A 1 / 20 scale train model weighing 14.6 kg weight connected to the carriage was launched at 400 km/h and safely stopped in a breaking box filled with foam beads. The developed model can lead to the design of safer and more durable infrastructure and train car bodies, and more optimized three-dimensional train nose shapes.

The maximum height of the crown produced when a single droplet impinges on a stationary liquid film was investigated numerically using the numerical analysis code JUPITER. Only We number, which represents the inertia force, and Eo number, which represents the gravity term, were changed in the analysis. The results show that the maximum crown height increases as the We number increases, and that when the Eo number is smaller than 0.4, the crown is not affected by gravity, but when the Eo number is larger than 0.4, the crown becomes affected by gravity. Until now, it has been thought that gravity has no effect on splash phenomena, but it was found that gravity affects the process of crown formation, and accordingly, gravity is thought to have an effect on splash as well.

Differential pressure type water level gauges are generally used to measure a water level in a reactor pressure vessel (RPV), but they may not be able to measure a water level correctly in severe accident environments. Therefore, we are developing a Clamp-on Ultrasonic Water Level Measurement Method that can measure a water level in a RPV even under severe accident conditions. In this study, we measured water levels using Clamp-on Ultrasonic Water Level Measurement Method in the range of 0 to 28 cm water level using a small laboratory test apparatus. The measuring section was made of a metal plate with a wall thickness of 10 mm, and its materials were aluminum, stainless steel (SUS303), and carbon steel (SS400).Ultrasonic transducers have a resonant frequency of 2 MHz, and the angle of incidence of the transmitted wave was measured under two conditions. We confirmed that the trend and degree of change of the received signal according to the water level in the vessel for each vessel material and transmitted wave, and showed that the water level can be obtained accurately from the received signals.

The test blanket modules for the ITER fusion reactor have been designed. As for Japan, the TBM has a complex structure for breeding tritium while cooling with water and is exposed to high temperatures, radiation, and magnetic fields during operations. One potential accident is the blanket module's Loss of Coolant Accident (LOCA). Currently, leakage detection is planned through differential pressure. Identifying leakage locations and developing rapid detection methods are necessary to improve safety. The authors propose using optical fibers wrapped around a mock blanket submodule and applying machine learning to frequency modulation of scattered light for leakage detection. This study aims to develop a method to detect internal leakage and external heating using linear optical fiber arrangements.

To reduce the computational demand in the best estimate plus uncertainty (BEPU) analysis, an accurate and inexpensive machine learning model is expected to be used to replace the high-fidelity RELAP5 code for rapid determination of the uncertainties on the figure of merit of interest. One of the problems associated with the application of machine learning is overlearning. Quantum circuit learning is the quantum analogue of classical deep learning, which is expected to be less prone to overlearning because the optimized parameters are bound by unitary transformations in the quantum circuit. In this paper, quantum circuit learning is applied to the BEPU analysis of the fuel peak cladding temperature (PCT) for a small-break LOCA scenario in PWRs. The parameterized quantum circuit is trained using a small number of the RELAP5 analysis results and the prediction accuracy of the 95th percentile value of the PCTs is investigated. By taking a large number of layers of parameterized quantum circuits depending on the complexity of the analysis target and applying a global optimization method to optimize the parameters, the 95th percentile value of the PCTs predicted by the quantum circuit learning is found to result in better accuracy and smaller variability than linear quadratic regressions.

Japan Atomic Energy Agency and Central Research Institute of Electric Power Industry have been conducting a project to develop safety analysis methodologies on metal fuel sodium-cooled fast reactors in the area of advanced reactors under the framework of the U.S.-Japan bilateral commission on civil nuclear cooperation since 2018. The project encompasses analysis methodology development and experiment on core bowing reactivity analysis, core damage accident analysis, and mechanistic source-term analysis. This report describes the project overview and the outcomes of five-year activities in Phase 1: 2018-2022.

To enhance a safety of sodium-cooled fast reactors, decay heat removal systems under natural circulation with a dipped-type direct heat exchanger (D-DHX) installed in a hot pool of a reactor vessel (RV) have been investigated. During the D-DHX operation, the thermal-hydraulics of RV is complicated because the coolant at low temperature from the D-DHX flows into the core and the radial heat transfer through coolant in the interwrapper gap among assemblies occurs.

We have been constructing the practical model for physics in the RV in the design study which can achieve a lower computational cost while maintaining prediction accuracy using the computational fluid dynamics code (RV-CFD). The applicability of RV-CFD previously was confirmed through several numerical analyses of steady-state in a sodium experimental apparatus named PLANDTL-1. In this study, to expand the scope of applicability of RV-CFD to the transient-state, we develop the non-equilibrium thermal model which considers the thermal inertia in simulated fuel pins.

The transient analysis simulating the power reduction due to reactor scram from the steady-state operation in PLANDTL-1 is conducted. The result shows the thermal-hydraulic behavior in the RV during the transient can be predicted, and the core temperature in the transient can be reproduced. Thus, the applicability of RV-CFD using non-equilibrium model to the transient analysis for PLANDTL-1 is confirmed. Its applicability for an actual reactor will be investigated in the future.

An evaluation method of gas entrainment phenomena due to free surface vortices has been developed for the design application of a reactor vessel of a sodium-cooled fast reactor. The method predicts vortex dimple by applying the vortex model to the flow field obtained from three dimensional hydraulic analyses of an evaluation area. In this study, the applications of the adaptive mesh refinement (AMR) method to a gas entrainment water flow experiment in a rectangular channel with advection vortices were examined to create analysis meshes automatically for gas entrainment evaluation. Transient analyses were carried out using refined meshes obtained from the applications of AMR methods under different initial grid size conditions. Then, the quantities related to vortex formation and the total computation cost were compared with the result from a transient analysis under a reference mesh with uniformly fine grids. As the result, it was confirmed that the variation of the total grid number is possible to use as a criterion to judge the refinement termination in the application of AMR, and the computation cost of transient analysis can be reduced by the application of AMR.

As one of the safety evaluation methods for a steam generator in sodium cooled fast reactors, a computer program called SWACS has been developed to calculate pressure wave propagation induced by sodium water chemical reaction under tube failure accident. This code consists of the modules for computing water leak rate under double-ended failure of heat transfer tube, propagation of initial spike pressure, and variation of quasi-steady pressure. Previous studies have improved the elemental analysis methods such as a gas-liquid two-phase flow model. In this study, the experiment on water discharging into liquid sodium was analyzed to validate the latest version of modules for initial spike pressure propagation and quasi-steady pressure variation. The results showed consistency with the measured pressure.

In the study of safety enhancements on advanced sodium-cooled fast reactor, it has been essential to evaluate the influence of buoyancy on pressure drop in a fuel assembly at mixed convection condition during natural circulation under the decay heat removal operation. In this study, the numerical simulations of the 19-rod and 91-rod bundle water experiments at low flow rate conditions were performed for the validation of a thermal-hydraulic analysis code named SPIRAL with the hybrid turbulence model. The influence of buoyancy on the velocity and temperature distributions was analyzed, and the applicability of the hybrid turbulence model to the pressure drop evaluation was investigated by comparison with the experimental friction factors.

Thermal fatigue cracking can initiate in tee pipes where high and low-temperature fluids flow. A numerical fluid-structure thermal coupled simulation was conducted to investigate the penetration flow phenomenon of the mainstream into the branch pipe at a T-junction. Additionally, dynamic mode decomposition (DMD) was performed on the temperature field to analyze the factors contributing to temperature fluctuations. The penetration of high-temperature mainstream into the branch pipe caused temperature fluctuations on the pipe inner surface. Relatively high temperature fluctuations were observed on the upstream side of the branch pipe wall. DMD of the temperature field revealed a temperature fluctuation of 66 Hz at the location where the mainstream and branch pipe flows collide, and approximately half of that, 30 Hz, at the right corner. Temperature fluctuations of 5.5Hz and 0.29Hz were observed in the penetration region. The collision of waves against the right corner caused temperature fluctuations on the branch pipe wall with a relatively low frequency of 0.29Hz.

Flow-accelerated corrosion (FAC) is a pipe wall thinning phenomenon caused by a combination of thermal-hydraulic, water chemistry, and material factors. The current management of the pipe wall thinning of Japanese nuclear power plants is based on the thinning rate and residual lifetime evaluated using the measured pipe wall thickness. While current management has the advantage of directly identifying the residual wall thickness of pipes and the timing of replacement and repair, there are issues with management for piping sections and systems where the actual residual lifetime cannot be accurately identified because it has not been measured or because it is difficult to measure. To rationalize the current management, we have been developing FALSET, a pipe wall thinning prediction software, to improve its prediction accuracy and to study its specific applications in wall thinning management. The reactor water cleanup system (CUW system) in a BWR plant, which is a self-managed system in terms of wall thinning management, is located in a high-dose area, and thus needs to be managed rationally while minimizing radiation exposure. In this study, we compared the residual lifetime of the CUW system of a BWR plant calculated using the initial thickness measurement and the predicted residual lifetime by FALSET, and examines the issues to be solved when the prediction method is applied to the wall thinning management of the self-managed system.

Flow-Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in nuclear power plants as a high priority. In one of the pipe rupture accidents caused by FAC in the past, it was reported that the swirling flow generated in continuous piping elements affected FAC behavior at the downstream of the orifice in power plants, but the parameters determining the FAC-related swirl intensity remained unclear. To add the effect of swirling flow to FAC and Liquid Droplet Impingement Erosion (LDI) Prediction Software for Pipe Wall Thinning (FALSET), which was developed by authors, the dominant swirl intensity parameters must be elucidated. In this study, a FAC prediction model downstream of the orifice due to the swirling flow generated in continuous piping elements was developed by numerical simulation. From the results, the geometric factor expressing the intensity of FAC increases with swirl intensity. Finally, the FAC prediction model was constructed by applying the relationship between the dominant swirl intensity parameters and the geometric factor.

In order to properly identify the pipe wall thinning in power plants, electric utilities have implemented management based on the pipe wall thinning management codes published by the Japan Society of Mechanical Engineers (JSME). However, there are some management issues, such as the inability to accurately evaluate the wall thinning rate in areas that are difficult to measure, so the introduction of wall thinning management using a wall thinning prediction method is positioned in the roadmap for the revision of the JSME codes. This paper summarized the advantages of using the prediction method, and proposed a concrete process for the management of the wall thinning using the prediction method. Furthermore, the timing of the measurement based on the prediction was evaluated based on the proposed wall thinning management process.

In this study, in order to theoretically analyze the strength and torsional rigidity of planetary gears, a mechanical equivalent model is proposed for planetary gears, 17 equations are derived based on the balance of forces of each component, and special software is developed. Force analysis of planetary type of planetary gears system is performed using special software to clarify the loads generated on each gear in the system. If the loads generated on each component are known, it will be possible to analyze the strength of planetary gears. In the future, we plan to further improve the mechanical model so that gear machining errors and tooth surface modifications can be taken into account, and to clarify the effects of gear machining errors and tooth surface modifications on the force distribution of planetary gears by developing special software.

The strain wave gearing was invented by Musser in the 1950s. This device has many advantages such as small size, lightweight, a large reduction ratio and a small backlash, so it is widely used in industrial robots and semiconductor manufacturing equipment. But design and strength analysis problems have not been solved completely since the complex deformation of the flex-spline used in the tooth engagements. In particular, strength analysis using models that consider balls has rarely been conducted. This study develops design software for strain wave gearing in the surrounding of AutoCAD. This software can make it possible to design the strain wave gearing automatically and reduce design calculation and drafting time significantly. Also, it makes it possible for less experienced designers to design the strain wave gearing freely. The developed software can also be used to study tooth meshing characteristics of the strain wave gearing. Strength analysis problem is also study in this paper by using SolidWorks' Simulation function, a 3D finite element method model that includes the flexible bearing balls is proposed to conduct tooth contact analysis of the strain wave gearing. Tooth surface pressure, principal stress at the tooth root of the flex-spline, and the surface pressure on the balls are analyzed.

In this study, a tooth profile design method is developed for a three-lobes strain wave gearing and the responsive design software is developed in AutoCAD surrounding. A three-lobes strain wave gearing is designed by the developed software. Then stress analysis is conducted for the flex-spline when it is deformed by the three-lobes wave-generator using specially developed finite element method software. This analysis is also conducted for the flex-spline when it is deformed by a two-lobes wave-generator in order to know the effects of the lobe numbers on the stresses occurred in the flex-spline. Based on the calculation results, it is found that the maximum load on the ball surfaces is increased by approximately 65% and there is almost on difference in the shear stress that causes diaphragm fatigue cracking failure when the two-lobes wave-generator is changed into three-lobes wave-generator. In addition, it was confirmed that the bending stress at the root of the tooth was reduced by about 20%.

In order to confirm the effect of the difference in module sizes of micro-cross-helical-gears on the load-carrying-capacity, we compare the failure modes of module 0.1 mm and module 0.2 mm. We carried out acceleration endurance test on a micro-cross-helical-gear under the lubricant dropping condition only at the start of the experiment. As a result, in case of module 0.2 mm, extremely minute wear powder was spread thinly over the entire tooth surface, which was quite different from the tendency of wear powder in modules 0.1 mm. Micro-crossed-helical-gear of module 0.2 mm had failed tooth tips due to progressive wear, module 0.1 mm showed progressive wear, but did not experience failures at the tooth tips. This is most likely due to the influence of the micro-crossed-helical gear specifications, especially the same tooth width. A comparison was also made in terms of the area of the contact ellipse, and it was found that the increase in contact area per step was larger for the module 0.2 mm. This means that the maximum Hertzian pressures increase per step is also larger, and the magnitude of the load applied to the tooth surface during a single test is also different for each module. Therefore, differences in modules may affect the area of the contact ellipse and the associated maximum Hertzian pressure, which may also have an effect on lifetime.

Chains are used in the case of difficult to transmit rotation or torque using friction wheels or gears over long distances between two axes. However, drawbacks such as decreased transmission efficiency due to friction, wear, vibration and noise, in addition elongation for wear occur under transmit conditions of high loads and high speeds. Previous studies have shown that the viscosity of lubricating oil affects the temperature rise of chains. It is believed that the formation of oil film between pin and bush is related. Therefore, this study evaluated differences in lubricating oil viscosity affect the wear of chains, focused on temperature rise of chain and wear of pin. Based on the experimental results, effect of lubricant viscosity on the wear characteristics of chains were discussed. From these discussions, it seems reasonable to conclude: (1) It was cleared that the temperature rise of chain was higher and the amount of wear increased with low viscosity oil compared to high viscosity oil. (2) The oil film thickness formed between pin and bush changes depending on the difference in the lubricant viscosity and the rotational speed of chain, and affects the frictional state during operation.

In this study, spur gear driving tests were conducted with the ultimate goal of developing a calculation method for predicting tooth flank wear. In order to determine how the initial roughness of the tooth surface affects the wear of the tooth surface, three types of test gears were manufactured and subjected to wear tests in which only the tooth surface roughness was different and other parameters, such as surface hardness, were kept as identical as possible. The tooth profile of each test gear was measured using a gear measuring machine, and the amount of change from before the experiment was calculated as the amount of wear. This paper reports the results and discusses how tooth surface roughness affects the amount of wear on the tooth surface.

Ball casters are widely used to transport heavy objects such as molds because they can move freely on a surface and they exhibit low friction. However, unlike ordinary rolling bearings, the movement of the balls that support the load is not restricted by a cage or raceway groove, and many aspects of the behavior of ball casters are unknown. To achieve even higher load capacities and lower friction, it is necessary to understand the load distribution and behavior of the balls and optimize the specifications and shape of such casters. To achieve this, the present study determined the load distribution through geometric calculations and measurement of running marks. The behavior of the balls was also investigated through multibody dynamics simulations and observations using a high-speed camera, and the frictional force was compared between the simulations and actual measurements. Based on the results obtained, a shape that combines low friction and high load capacity was proposed, and its effectiveness was confirmed through experiments.

The purpose of this study is to simplify the tooth flank design of conjugate gears meshing with involute cylindrical gears on non-parallel axes. In this study we have so far clarified and reported that a face gear, which is a gear conjugate to an involute cylindrical gear, has a straight meshing contact line of action in three-dimensional space. The meshing point between the involute cylindrical gear and conjugate gear proceeds at a constant speed along the straight line of action. The straight line of action is continuous and exists as a curved surface. We named it the meshing contact surface of action. We will discuss the meshing between involute helical cylindrical gears and bevel shaped conjugate gears with crossed axes and tilted axes. In this report, as a first step in researching this complex gear, we use generation analysis from the cross-sectional tooth profile of an involute helical gear, to clarify a method for numerically calculating the tooth profile of a bevel gear.

Involute curves are mainly used for gears. However, involute gears likely occur tooth undercutting, pointed tooth, and reduction in contact ratio as number of tooth decrease. On the other hand, cycloid gears, similarly involute gears, can transmit motion at a constant speed ratio. Although cycloid gears are not suitable for power transmission because of significant increase in contact stress at the pitch point. In this study, we designed an inconvertibility cycloid gear, an involute- cycloid composite gear, a modified cycloid gear and an asymmetric involute gear, which gears have small tooth number. Inconvertibility cycloid gears prevent contact at the pitch point by using epi-cycloid tooth profile for the pinion and hypo-cycloid one for the wheel. Involute-cycloid composite gears use an involute curve near the pitch point. Modified cycloid gears remove the curve near the pitch point attempt to reduce contact stress. Asymmetric involute gears have different pressure angles between the working flank and the non- working one to prevent tooth undercutting at the tooth root and pointed tooth at the tooth tip. Driving tests were accomplished using these gears with the power absorption gear testing machine, and discussed the driving performance.

Research on transmission error (TE) for fishing reel in previous reports has made it possible to estimate fishing reel sensation with high accuracy from TE waveforms. However, there are still cases where the results of the estimate differ from human judgement. In the previous report, the TE waveform was intentionally changed to investigate the effect on the fishing reel sensation felt by the human fingertips. The results showed that sawtooth waves have a significant effect on the sensation of fishing reels at the same level as the amplitude variation. In this study, we focused on the sawtooth wave of the TE waveform and verified whether the accuracy of the estimation of the fishing reel sensation could be improved by considering the phase of the sinusoidal peak position after Fourier transform. The estimation accuracy of the fishing reel sensation was significantly improved by adding weights considering not only the phase of the peak position but also its sign.

To create a sustainable society, efforts are being made to reduce CO2 emissions from transportation equipment, including automobiles. To improve fuel/electric efficiency, lightweight structures with high strength and stiffness are desired. Specifically, to enhance stiffness, rather than adding members that increase mass, an approach involves focusing on joints where stress is likely to concentrate and re-evaluating the structure and number of joints. We have investigated the stiffness of bolted joints and have shown that the joint area could be a parameter affecting stiffness. Since spot welding is the primary joining method in automobiles and the use of adhesive bonding has been increasing, we compared the shear tensile stiffness of bolted joints, spot welded joints, and adhesive bonded joints. As a result, we found that there is a qualitative proportional relationship between stiffness and joint area regardless of the joining method. However, it was also found that joint area alone cannot fully explain the stiffness.

Screw loosening tests are often performed with a size of about M10. Ease of load application to screw fasteners and ease of measurement of axial force for detecting loosening are the main reasons. In comparison with that, in the loosening test of small diameter screws, since the sample of the test is small, it is difficult to detect the load applied to the screw fastener, addition of displacement, loosening, and the like. This study proposes a method of looseness test and a method of detecting looseness for a small diameter screw of about M1. In this study, we proposed a method to test for screw loosening using inertia. We also proposed a method to detect the occurrence of looseness during the test. Experiments were performed to confirm that they were effective.