This research presents a numerical simulation of flow induced cavity noise using the general-purpose simulation software COMSOL Multiphysics. Flow induced cavity noise is caused by turbulent flows, which has been the focus of numerous research studies during the past few decades. In this study, the Detached Eddy Simulation (DES) approach is used to compute the unsteady behavior of the vortex flow field. The DES approach is a hybrid method between the Reynolds Averaged Numerical Simulation (RANS) and the Large Eddy Simulation (LES), where the RANS model is used in the boundary layer and the LES treatment is applied to the separated regions. Therefore, the DES approach provides the accuracy of the LES method with substantially less computational effort. In this paper, the DES model and the Lighthill’s acoustic analogy are coupled to capture the cavity flow-noise in a ducted system. Finally, the results are verified with the experimental data reported by Lafon et al ^[1] in 2003.

CFD was used to investigate turbulent flow in circular pipes and square pipes. It was found that roughness in the calculation boundary generated disturbances and increased the pressure drop. A period of time during which disturbance was applied and a period of time during which the flow was left without disturbance were set alternately, and the pipe friction coefficient was calculated in the latter time period. Using the mesh length-to-diameter ratio and the Reynolds number as parameters, the values of the pipe friction coefficients calculated were compared with the values of the Moody diagram. Without using any knowledge obtained from experiments, it was possible to get a pipe friction coefficient that was consistent with the Moody diagram.

In recent years, with the improvement of technology, the Shinkansen have become faster and the performance in the intake and exhaust systems of automobiles have been remarkably developed. On the other hand, shock waves generated by high-speed flow in bullet trains when they pass through tunnels and inside the intake and exhaust systems are expected to have various adverse effects. Therefore, it is essential to measure the strength and propagation direction of shock waves to improve equipment performance. In this study, we measured the strength and direction of propagation of shock waves under conditions that anticipate internal flow, such as in a turbo machinery. The sensor used in this study is a diaphragm type pressure sensor with a strain gauge attached to the inner surface of the pressure-sensitive portion. Based on the pressure history of this pressure sensor, rosette analysis was performed, and the results were compared and discussed under two conditions, one in stationary fluid and the other in flowing fluid.

The purpose of this research is to develop a test method to evaluate the characteristics of non-Newtonian fluid by using MPS (Moving Particle Simulation) and equipment. Brookfield type viscometer is widely used as a method to evaluate the characteristics of non-Newtonian fluid. The device can evaluate the viscous properties of fluids well within a certain range. However, due to the measurement principle of the device, it is difficult to evaluate the characteristics of fluid that slip on the surface of the spindle. Therefore, in this study, we investigated a test method that may be able to evaluate the viscous properties of even the above-mentioned fluids. Therefore, we focused on the inclined flow test recently proposed in the civil engineering field. Inclined flow test is applied to evaluate the shape of fluid collapse. Newtonian fluid was used as the reference for the analysis, and pseudoplastic fluid was used as a representative of non-Newtonian fluid. By unifying the flow distance and analyzing the curvature of fluid collapse, it might be possible to evaluate index of power law model.

An experiment was conducted to investigate on a vibrating pipe flow with streamwisely-uniform blades aiming at the heat transfer enhancement. The experimental apparatus changes the Reynolds number from turbulent to laminar flow as it enters the test section from the entrance section. The test section is oscillated with a frequency of 100 Hz and amplitude of 800 μm. The vibration was generated by means of three piezoelectric actuators. There are a pair of uniform blades facing each other in the flow direction and their angles respect to the direction of vibration θ were varied as 0°and 90°. Particle Image Velocimetry (PIV) measurements were performed on a cross section perpendicular to the flow direction of the test section. As a result, the difference between the periodic and the fine vortices contributed to the increase in the friction drag coefficient.

To evaluate the pressure response of pressure-sensitive capsules in the hypoxic region, Ru(dpp)3 absorbed in microcapsules (B6C, E2C, B25C and AF6C) were used. The four pressure-sensitive capsules were found to gradually decrease from 0.1 kPa to 1.5 kPa. Comparing these capsules, B25C and AF6C showed better pressure sensitivity. This suggests that the average particle size may affect the pressure sensitivity of the pressure-sensitive capsules. The pressure distribution on the wing of a small rotating blade was also measured by PSP. An area of high pressure was observed on the leading edge of the wing, and an area of low pressure was observed on the trailing edge. Since pressure sensitivity is higher at lower oxygen partial pressures, when a pressure change occurs, the region of high pressure should be wider at lower oxygen partial pressures than at higher oxygen partial pressures. However, the present results show that the regions with high pressure gradient become wider as the oxygen partial pressure increases. This may be due to the fact that even at high pressure sensitivity, at oxygen partial pressures as low as 0.25 kPa, there are fewer oxygen molecules needed for oxygen quenching and the sensitivity to pressure increase is lower than at 0.50 kPa, where there are enough oxygen molecules. The error areas on some of the wings may be due to unevenness created during PSP fabrication; such pigment unevenness during PSP preparation or fan installation may cause significant changes in luminescence intensity, resulting in errors in the image.

The flow field of an annular jet impinging on the wall was experimentally studied. Experiments were performed at the Reynolds number based on the jet exit velocity and the nozzle outer diameter of Re=67,000. Varying the distance from the nozzle to the wall, four types of flow pattern, from G1 to G4, were identified from the measurements of the central stagnation pressure and the radial pressure distribution. The velocity field between the nozzle and the wall was obtained by LDV and PIV. When the wall impingement distance is large (flow pattern, G1), a single forward stagnation point was formed at the central area of the wall by the merged jet after flowing around the re-circulation zone attached behind the nozzle inner body. For the intermediate impingement distance (flow pattern, G2), a reverse stagnation point which is formed by a large scale re-circulating flow between the nozzle and the wall, and a circular forward stagnation line which is formed by the jet impingement, were found to appear. It was also observed that the radial velocity fluctuation increased over a wide area of the impingement surface in the flow pattern of G2.

Natural convection in a horizontal slot with surface corrugation was examined experimentally at Rayleigh number based on the slot half-height below Ra = 300. The sinusoidal surface corrugations whose amplitude was 2.5% of the slot full-height and wavenumber was α_w = 0.5 - 2 was applied on the bottom surface while upper surface was kept smooth. Both walls were heated uniformly at different temperature. The results showed that surface corrugation promoted the occurrence of thermal convection significantly, that is, a pair of convection rolls whose wavelength was the same as that of corrugation was observed even at Ra = 50, about 1/4 the critical value for smooth slot. Velocity of convection rolls increased monotonically with Rayleigh number in sub-critical regime, in which rolls over α_w = 1.5 took the maximum. It was also found that the rolls became three dimensional at and around the critical Rayleigh number.

Since a fuel cell stack consists of many cells, it is important to distribute fuel to each cell efficiently to improve performance. In the present study, disc-type solid oxide fuel cell (SOFC) model with stacked hollow disks was used to investigate optimum conditions for uniform flow distribution by introducing a cylinder installed coaxially inside the circular supply tube. The velocity fields in the parallel-stacked disk channels are measured by using a particle image velocimetry (PIV). The volumetric flow rate was calculated from the velocity profiles, and distribution of the flow rate through each disk channel are also examined. From the measurement results, it was shown that narrowing the stack spacing of the disks improved the flow uniformity, suppressed vortices at the inlet of the disk channel, and produced a uniform flow field. Furthermore, it was found that equal distribution could be achieved more effectively by installing a cylinder with a diameter that occupies about 16% of the circular supply tube cross-sectional area.

Some centrifugal compressors have positive slope characteristics in their performance curves, which is a region with unstable operation. According to the system configuration, surging phenomena, which develop from a swirling stall and cause dramatic changes in flow rate and pressure, may occur. The surging phenomenon is investigated through experiments in this study. To detect the surge inception, the behaviors of flow rate time traces measured at the inlet of the compressor system are reconstructed on the phase portraits. To suppress the instability phenomena, the motor rotation speed is adjusted by PID control.

In this research, we investigated the effect of balance holes in centrifugal impellers on axial dynamic characteristics. To measure the unsteady fluid force applied to the impeller, we performed the axial oscillation test for a model impeller for rocket turbopumps with and without balance holes. Additionally, we carried out CFD-based investigations and compared the results between experiments and computations. The axial dynamic characteristics predicted by the unsteady simulations generally agree with that of the experiments. The axial thrust amplitude under oscillation becomes greater with balance holes than without balance holes because of the additional supply of leakage flow from balance holes. We also found the phase difference between axial displacement and thrust varies depending on the presence or absence of balance holes. From these results, we confirmed the change of leakage flow due to balance holes resulted in the change of pressure distribution at the back of the impeller and dynamic characteristics for centrifugal pumps.

The increase of turbine blade loading by the increase of blade turning angle is an effective method to improve the efficiency of gas turbines. However, it also increases the secondary losses caused by the intensifications of the horseshoe vortex, the passage vortex, and the leakage vortex, and consequently leads to the significant degradation in the aerodynamic performance of turbine. Therefore, the applications of any useful techniques to suppress the increase of aerodynamic losses are absolutely required for the development of the highly loaded turbine cascade in practical use. The squealer tip, which has a cavity on the blade tip surface, is one of the techniques to reduce the leakage flow and has been verified to be effective for the conventional turbine cascade. In this study, the performance tests were performed for the ultra-highly loaded turbine cascade (UHLTC) with three kinds of squealer tip, which were different in the cavity depth, by using the small sized wind tunnel test rig for an annular cascade. The test results showed that the application of the squealer tip with minimum cavity depth contributed to the enhancement of aerodynamic performance of the UHLTC. It increased the torque but had almost no effects on the efficiency due to the increase of the loss in the high flow coefficient region. On the other hand, its application improved the efficiency in the low flow coefficient region because of the reduction of the loss as well as the increase of the torque.

An increase of turbine blade loading by increasing the blade turning angle is an effective method to improve the performance of gas turbine, which enables to reduce a turbine in size and weight. However, it also intensifies the secondary flows due to the increase of pitchwise pressure gradient and increases the associated losses. Since the pressure side leg of horseshoe vortex entrains the endwall boundary layer and grows into the passage vortex, the reduction of the horseshoe vortex leads to the reduction of the passage vortex. The application of a fillet to the leading edge endwall junction (LEF) is known to be effective for the reduction of the horseshoe vortex. The configuration of the LEF is defined by some geometrical parameters such as the fillet height and the fillet width, so it is necessary to investigate the effects of these parameters on loss generation. In this study, the LEF was applied to the ultra-highly loaded axial turbine linear cascade (UHLTC) with the turning angle of 160 degrees. The effectiveness of the LEF on the UHLTC was examined with the parameter of the fillet width by performing the internal flow measurement, the endwall surface pressure measurement and the oil flow visualization. The experimental results showed that the application of LEF to the UHLTC suppressed the passage vortex as well as the horseshoe, and consequently reduced the secondary flow losses. In addition, the increase of the fillet width enhanced the suppression effect caused by the LFE.

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 secondary flow was evaluated by flow visualization experiment. As a result, it was possible to confirm the high film cooling performance in the new original shape.

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 experiment and heat transfer experiment. As a result, it was possible to confirm the high film cooling performance in the new original shape.

Normally, lubrication in linear motion guidance is performed by having the entire load area supplied with lubricant by the rolling elements supplied with lubricant during long strokes. However, during minute strokes, the rolling elements cannot pass through the end plates at both ends of the carriage, so lubrication oil cannot be supplied to the entire load area, resulting in wear and fatigue of the rolling elements. Therefore, we devised a method to enlarge and utilize the gap between the carriage and the rail. By enlarging the gap through additional machining, we believed that lubricant could be supplied to the entire load area even with minute strokes. In the experiment, the carriage was cut in half and a porous material was installed. The results showed that with soft grease, the larger the rotation angle, the better the diffusivity, and the larger the number of rolling elements to be supplied, the easier it was to supply grease to the entire load area. With hard grease, it was difficult for the grease to exit the porous material, and the hard grease hindered the motion of the rolling elements, resulting in poor grease diffusivity. Future studies should consider the combination of porous material and grease.

It was reported that acoustic wave enhanced the adsorption speed of Silica gel by experiments and low frequency oscillating flow also would enhance the adsorption speed by CFD simulations. The objective of this study is to construct low frequency oscillating flow generator and to confirm the effect of the oscillating flow on the adsorption. Two blowers are involved to create oscillating flow with reverse flow, which is necessary for the adsorption enhancement. The adsorption amount was measured with steady flow and with the oscillating flow. According to the results, it was observed that the effect of adsorption enhancement depended on the ratio of flow velocity and the condition of air supplied from downstream side.

In this study, a hybrid rotary filter is proposed as one type of oil mist collector to be installed on a machine tool. To understand the performance of the filter, the flow characteristics inside the device were predicted using CFD. In predicting the flow characteristics, three conditions were analyzed: the condition under which no unpurified air leaks from the device, the amount of pressure loss downstream relative to upstream, and the length of the stream line passing through the filter. The results show that as the rotation speed of the filter increases, air leakage and pressure loss are eliminated and the length of the streamlines increases. The results clarify the necessary conditions for the design of the hybrid rotating filter, along with its performance.

Vortex tube is a simple device that can simultaneously produce cold and warm air when compressed air into it. It is widely used industrially mainly for the purpose of cooling things. The aim of the preset study is to have ideas what are the factors that cause vortex tube’s energy separation. In this experiment, the pressure, temperature, and flow rate of the gas flowing in and out of the vortex tube were measured. And the energy balance flowing in and out of the vortex tube is considered. The larger the cold flow fraction, the smaller the enthalpy inflow and outflow, and the greater the internal loss. This is thought to be due to the mechanism for adjusting the cold flow fraction, and increasing the cold flow fraction increases the flow resistance of the vortex tube.

There are two types of flying cars integrated and combined with a drone. The combined with a drone type has the advantage of being able to run directly on existing roads by detaching a drone. Therefore, we developed the first prototype of combined type with a takeoff weight of 0.1 kg in 2021. We developed the second prototype and the third prototype with a takeoff weight of 2.5 kg in 2022. By changing the place of the drone motors from the arms to the top of the 200-mm newly inserted extension support rods, the drone has stronger ability to resist wind and improved flight stability．Furthermore, it was proved by flow simulation that the lift of the second prototype was increased by 4.0% with the above changing the place of the drone motors.

The vortex structures in the wake behind a circular disk, as a representative bluff body, were investigated by PIV measurement. Stereo PIV results perpendicular to the mainstream direction were visualized in the iso-surface of Q-criterion reconstructed three-dimensional vortex structure. It was found that the vortex structure at Re = 650 has a feature of staggered-type I with small vortices. In addition, velocity fluctuations in the wake behind a circular disk were decomposed into various scale structures by phase-averaged technique. The large-scale structures in the wake of circular disk were shown as alternatingly a series of connecting hairpin vortices. Small-scale structures revealed regular small vortices between adjacent hairpin vortices. Furthermore, we investigated the formation mechanism of the staggered-type I in the wake. When the vortices were separated, recirculation region was split into two vortex structures. One of those structure flowed downstream, rolled up as a vortex. The other went upstream, generating counter-rotating vortex with another recirculation region.

The velocity field around a cylinder was measured by PIV when the cylinder was moved in a Poiseuille flow in a circular pipe. The cylinder was placed coaxially with the circular pipe and moved at a constant speed in the axial direction. In the present experiment, the velocity distribution and flow rate in the gap between the circular pipe and the cylinder were investigated using the moving speed and diameter of the cylinder as parameters. It was found that the flow rate in the gap decreased with increasing cylinder movement speed, and the rate of decrease was significantly greater for larger cylinder diameters. Moreover, it was shown that the increase in the cylinder diameter also decreases the flow rate in the gap. From these results, it was suggested that the flow rate in the gap can be summarized using an approximate straight line with respect to the cylinder movement speed or the cylinder diameter. It was shown that as the movement speed and the diameter increased, the flow rate in the gap became more strongly affected by these parameters.

Evanescent light is exponentially decaying light that leaks onto a total reflective surface. To generate evanescent light, a pulsed laser pulse was injected into the glass-water interface, which caused the water placed on the prism to scatter. This phenomenon was found to be due to ablation caused by the enhancement of the electric field due to the superposition of the incident and reflected light inside the water-air interface. To generate the electric field enhancement in a smaller area, gold nanoparticles were placed on the glass surface, and ablation was successfully induced by the electric field enhancement caused by the interaction between evanescent light and the gold nanoparticles.

A typical anti-wear additive, zinc dialkyldithiophosphate (ZDDP), has been utilized for many types of lubricants. ZDDP is known to form reaction film by direct contact between sliding two substrates and protects adhesion wear. However, there are few reports about in situ observation of tribofilm formation due to difficulty in investigating the formation process of the tribofilm in nanoscale. Recently, Gosvami et al. observed the growth process of the tribofilm formed by ZDDP at the contacts of single asperities using a novel in-situ atomic force microscopy (AFM) method and suggested that increasing contact pressure and temperature promoted the growth of ZDDP tribofilm. In addition, we confirmed the promoting of tribofilm growth by increasing surface roughness. However, the promoting parameter on tribofilm growth has not been revealed. In this study, we used seven steel sample with different roughness and conducted in-situ AFM in ZDDP containing oil at 120 ℃. As a result, we confirmed the summit radius influenced the growth rate of ZDDP tribofilm. This suggests that the summit radius is a key parameter of tribofilm growth.

This report deals with a method for comprehending real contact situation by measuring complex refractive index in contact surface. For the contact surface where spherical samples were pressed against a glass plane in air, the distribution of complex refractive index was measured experimentally and was estimated by Hertz contact theory and the optical model in which the multiple reflections inside the gap between surfaces were considered. For the BK7 glass lens sample, the measured index was equal to the physical property in the contact and non-contact region and was accounted successfully for by the multiple interface model in the region where the index slowly changed. For the silicon lens sample, the measured index was not equal to the physical property but showed a proper value in the contact region. From the above it is suggested that this method enables identifying sample material as well as judging contact situation.

Since semiconductor manufacturing equipment does precise manufacture, the equipment can stop operation due to slight floor vibration. Accordingly, it is necessary to remove micro floor vibration in order to operate equipment properly. We have developed external vibration control device with piezoelectric actuator. By using this device, we demonstrated 78 % vibration elimination effect in horizontal 1 axis direction. However, control device which eliminates floor vibration of multiple direction is required in order to apply the device in factories. Therefore, the objective of this research is to develop the vibration control device which controls multiple degrees of freedom. In this paper, we firstly installed new piezoelectric actuator in a different direction, aiming to control 2 horizontal and 1 rotational axis. Then we demonstrated the device does not interfere with other axis during control. After that, we tested the control performance of 2DOF by horizontal 2 axis control. And lastly, we evaluated and improved 3DOF control performance by adding 1 rotational axis.

Known to be hundreds of times more efficient than single-phase heat conduction and convection, nucleate boiling is a reliable heat transfer scheme for high-heat-flux applications such as nuclear reactors and semiconductor cooling. Due to its multiphase multi-scale nature, however, boiling heat transfer lacks a complete understanding of the many underlying physical mechanisms for its superior efficiency. It remains unsettled a topic in the heat transfer community as regards how bubble dynamics affects heat transfer performance. The aim of this work is to develop a data-driven diagnostic tool for fast detection of bubble behavior. Convolutional Neural Network (CNN), which is often relied on to solve problems involving classification and identification of objects in images is adopted in this study. Specifically, CNN is used to analyze high-speed infrared thermometry-generated distributions of heat transfer coefficient on a boiling surface. The deep learning framework manages to identify the microlayer region underneath growing bubbles as marked by enhanced heat transfer. Based on the collected data on the bubble growth time and maximum radius of microlayer, a heat transfer model is built to assess the latent heat transport via microlayer evaporation.

The aim of this study is to investigate the effects of twisted tape insert on the refrigerant horizontal evaporator tube on pressure drop increase and heat transfer enhancement. R410A was used as the refrigerant. Experiments were conducted under seven different tape insert conditions: five types of twisted tape with different pitches, flat tape without tape twist and smooth tube. Pressure drop in the test section and heat transfer coefficient were measured by varying the refrigerant quality under mass velocity conditions of 360-630 kg/m²s. Insert of twisted tapes resulted in an increase of the pressure drop in all conditions, but the increase ratio from the smooth tube decreased as the twist pitch ratio H/d increased. On the other hand, the effect of tape insert on heat transfer enhancement was more pronounced in a dryout region where the refrigerant quality was above 0.85, and the increase ratio of the heat transfer coefficient compared to the smooth tube increased up to about 1.7 at a high mass velocity over 500 kg/m²s.

Direct contact condensation (DCC) is a phenomenon that occurs when steam is injected into a subcooled water pool and is an integral part of many industrial devices. However, the actual phenomenon involves non-condensable gases in the steam, and there has been insufficient research on how non-condensable gases affect direct contact condensation. Therefore, the purpose of this study was to clarify the bubble collapse behavior of vapor bubbles containing non-condensable gas by DCC, and the bubble collapse behavior was confirmed using a high-speed video camera. The images show periodic bulging and necking, and the contraction speed at the point of necking was slower in the bubble plume with a higher air mass fraction. The number of microbubbles produced in the rising bubble plume was suppressed in the high air mass fraction plume. Thus, there is a negative correlation between the contraction rate of the bubble plume and the size of the generated bubbles.

Weakly nonlinear propagation of pressure waves in initially quiescent liquids containing many spherical microbubbles with phase change is theoretically studied. In particular, we focus on the effect of phase change across the bubble–liquid interface. Gas inside bubbles is composed of air as the non-condensable gas and water vapor as the condensable gas, and the diffusion of gas inside bubble is not considered. The liquid density and temperature are assumed as constants. However thermal boundary layer in liquid phase is considered, and the liquid temperature gradient is treated as a variable. From perturbation analysis using basic equations based on a two-fluid model, the Korteweg–de Vries–Burgers equation is derived. The phase change contributes to the nonlinear, dissipation, dispersion, and advection effects of waves. However, the result of the effect for dissipation effect is different from that in the previous study, and it is considered that treating the liquid temperature as a variable is necessary.

In recent years, as electronic devices have become more sophisticated, there has been a growing demand for highly efficient heat transport devices. In this research, as a new heat transport device, we have created a mechanism in which soft matter slides through a pipe. This sliding is expected to make the temperature boundary layer thinner in the pipe and to transport more heat than a dream pipe due to heat conduction with the pipe wall. In this experiment, the PIV method, LIF method and temperature measurements using thermocouples were used to elucidate the heat transport phenomena in sliding. The experimental results showed that heat conduction between the pipe and the soft-matter and the fluid flow behind the soft-matter caused the temperature change due to sliding. The temperature change of the fluid flow behind the soft matter was more dominant than that of the pipe contact.

In this research was performed an evaluated heat transport characteristic of simulated semiconductor heat flux conditions in thin plate type parallel tube heat transport device by using alcoholic solutions, in order to investigate the relationship between heat transport characteristics and internal fluid flow, it was conducted heat transfer experiment and internal flow visualization. As a result, the heat input and cooling flow rates were changed, the internal flow pattern and affecting the heated part wall temperature.

As the inlet temperatures of gas turbines are becoming higher to achieve higher thermal efficiency, it is essential to improve the cooling techniques for turbine airfoils. Film cooling is one of the cooling techniques, which is adopted at the cutback surface of the trailing edge of the turbine airfoils. Our previous study of large eddy simulation of channel flow showed that the heat transfer performance of the cutback surface with teardrop dimples was higher for the pulsating cooling than the steady cooling flow. This study experimentally focuses on the heat transfer performance of pulsating cooling flow over the cutback surface with teardrop-shaped dimples. Heat transfer measurements were performed by transient technique with compensation of three-dimensional heat conduction. Three types of cutback surface geometries (smooth, teardrop-shaped dimples of 0deg staggered arrangement, and 30deg in-line arrangement) were examined. Pulsating conditions were three types (St/St₀=0.3, ΔU_c,rms/U_c=5%), (St/St₀=1.0, ΔU_c,rms/U_c=5%) and (St/St₀=0.3, ΔU_c,rms/U_c=10%). For the smooth surface, the effect of pulsation was within uncertainty. 0deg staggered arrangement surface, pulsation of St/St₀=1.0, ΔU_c,rms/U_c=5% increased Nu_m/Nu_∞ by 0.2% (within uncertainty), decreased η_m by 7.0%, and decreased NHFR_m by 12.0% compared with the steady flow. 30deg in-line arrangement surface, pulsation of St/St₀=1.0, ΔU_c,rms/U_c=5% decreased Nu_m/Nu_∞ by 6.4% (within uncertainty), decreased η_m by 4.3%, and decreased NHFR_m by 11.2% compared with the steady flow. In addition, 30deg in-line arrangement surface, pulsation of St/St₀=0.3, /U_c=10% increased Nu_m/Nu_∞ by 9.3%, decreased η_m by 0.1 %, and increased NHFR_m by 6.0% compared with the steady flow, but all changes were within uncertainty.

It has been experimentally found that the flame shape of hydrogen, methane, propane swirling premixed lean flame are different. In this study, adiabatic numerical simulations of swirling lean methane premixed flames were carried out with the diffusion coefficient of methane set to thermal diffusivity weighted by the reciprocal of the Lewis number. As a result, it was found that when the Lewis number of fuel is lower than unity the flame shape is same as the methane flame in former studies. On the other hand, when the Lewis number of fuel higher than unity, the flame shape is same as propane. As a result, we concluded that the difference of the flame shape observed in our former studies is obviously due to the effect of Lewis number.

In this study, the possibility of ultra-diluted combustion of counterflow flames was investigated by numerical calculations using three counterflow flame models. As a result, the response curves of counterflow diffusion flame, counterflow double flames, and counterflow triple flames were produced separately, and the comparison shows that the triple flame is more difficult to extinguish than the double flame and diffusion flame. Then by chemical analysis, we found an important reaction which can be used as a criterion for determining the flame pattern of PPFs. Furthermore, as the dilution rate increases and extinction approaches, the double flame becomes a diffusion flame and the triple flame becomes a diffusion flame with a lean premixed flame. This characteristic inspired us to design a new partially premixed counterflow flame with similar extinction characteristics to the triple flame.

In recent years, internal combustion engines have been widely used in automobiles and power generators. However, in order to realize a sustainable society, it is necessary to reduce carbon dioxide emissions by using alternative energy sources such as hydrogen and biofuels, and to improve thermal efficiency by improving existing internal combustion engines. As one of the methods to improve thermal efficiency, we are studying a multi-stage impinging injection method that combines multi-stage injection in a heterogeneous combustion field and the impinging method. The use of multi-stage impinging injection method suggests the possibility of reducing unburned fuel components and improving combustion by controlling the ignition delay time. In this study, in order to examine the combustion improvement effect of the multi-stage impinging injection method, we investigated the effects of premixing and fuel atomization by changing the fuel injection rate on the combustion characteristics from the viewpoints of heat release ratio, total burning time, and ignition delay.

This research aimed to reduce NOx by injecting an aqueous ethanol solution into the intake pipe of a diesel engine. Previous studies have revealed the effects of aqueous solution concentration and intake pipe temperature on combustion products. In this study, we focused on the injection pressure of aqueous ethanol solution and also investigated the spray particle size and engine load. As a result, increasing the injection pressure reduced the spray particle size, and the latent heat of evaporation reduced NOx. Furthermore, it was confirmed that NOx concentration was reduced by 44% when the without engine load and 12% at high engine load of 1800W, respectively.

To achieve the in-situ imaging of reaction-diffusion phenomena during aqueous acid-base reactions, regression models constructed based on near-infrared (NIR) spectroscopic data measured using Fourier transform infrared spectroscopy were transferred to the image construction of HCl, NaOH, and NaCl concentrations through multivariate calibration standardization methods. In order to find the optimal method of model transfer, we compared the transfer performance of three methods: direct standardization (DS), spectral space transformation (SST), and calibration model transformation based on canonical correlation analysis (CTCCA). As a result, the transfer performance of DS was the best; the root mean square errors of prediction were 0.131, 0.069, and 0.027 M for HCl, NaOH, and NaCl, respectively. This result indicated that the proposed algorithm was a promising calibration transfer method for the NIR imaging.

Graphene is an atomic layer material with interesting properties due to the regular arrangement of carbon elements. Graphene is prepared by chemical vapor deposition (CVD) on copper or nickel thin film surfaces. Graphene is expected to be effective as a corrosion-resistant film due to its high gas barrier property. In this study, we explored the conditions for graphene deposition on the surface of steel plates with a thickness of 3.0 mm using the chemical vapor deposition (CVD) method. Although graphene deposition on thin steel sheet surfaces with a thickness of about 0.2 mm has been reported from previous studies, graphene deposition on thick steel sheets with a thickness of 3.0 mm has not been technically established. The deposited graphene was confirmed by optical microscopy and Raman spectroscopy. The tensile strength of the graphene-coated steel was also evaluated by tensile strength evaluation tests, and it was confirmed that the maximum stress was about twice that before the coating treatment.

The near-infrared (NIR) imaging of aqueous acid-base reaction using concentration regression models, wavelength selection algorithms, spectra transfer, and fitting is presented. The near-infrared spectra and concentration regression proposed methods of each acid, base and salt were converted into near-infrared images of concentration and diffusion fitting predictions. The study aims to qualitatively investigate the aqueous ionic effects of acid-base solutions using near-infrared absorption of spectra and images. The comparison was based on the acid-base formed salt concentration images during neutralization reaction between acids of H2SO4 and HCl, bases of NaOH and KOH, and salts of Na2SO4 and KCl.

This paper reports on the measurement of material spectra of acrylic plate and glass plate using a plasmonic spectrometer. Portable spectrometers are needed for more diverse applications of spectral analysis. This spectrometer has gold diffraction gratings on a n-type silicon wafer and is suitable for miniaturization because it completes the spectroscopy on the surface of the photodetector by using surface plasmon resonance. However, it has not been applied to spectral measurement of materials other than gases. Here, we measured the transmission spectra of acrylic and glass plates by the spectrometer with a plasmonic photodetector. We measured the responsivity to near-infrared light over a range of angles and at different wavelengths. We also measured the photocurrent due to the light under spectroscopy and performed matrix calculations for spectroscopy. The transmission spectra calculated were compared with the transmission spectra obtained with a conventional Fourier transform infrared spectrometer. The maximum error in the transmission spectrum was 22 % from 1250 nm to 1410 nm and the results calculated for this wavelength range were accurate. In conclusion, the spectrometer and continuum light can measure material spectra in the range. This research contributes to the realization of compact sensing system using the spectrometer that can analyze various material.

In grinding, the condition of the tool work surface affects the accuracy and roughness of the workpiece. There are various methods for evaluating the tool work surface. In this study, we used a polarization camera to evaluate the state of abrasive grains falling off, cracking, and wearing on the working surface of the grinding belt. A polarizing camera is a camera that can easily utilize polarization technology for one-shot imaging by polarizing elements. A polarization camera can obtain a DOLP（Degree of Linear Polarization) , an AOP(Angle of Polarization), and an ADOLP(Angle and Degree of Polarized Light) or reflection removal image combining them. Image processing was applied to the obtained images, and the state of the abrasive grains on the tool working surface was evaluated. The experiment was performed using a grinding belt. As a result, it became clear that the state of cracking and wear of abrasive grains can be evaluated by using a polarization camera.

We report the instantaneous physical evidence of detachment of residual φ80 nm Au particle due to the cavitation effect approaching during enforcing 1.1 MHz waves, which was clarified by using both of evanescent light field and dark field with duplicated the non-contact cleaning process of the surface to be cleaned.

The removal of particles on a wall surface by polyvinyl alcohol (PVA) roll brush was experimentally investigated as the fundamental study of wafer cleaning process. As the test particles, fluorescent silica powder were used. Change of the particle number near the wall surface before and after passing through the brush was investigated. Ejection of particles from the brush to the cleaning water was also estimated. Particles were removed by brush passage, however the particles re-adhered from the brush to the surface. It was also found that removed particles adhered to the surface on the inside of the brush and were ejected to the cleaning wafer at the next passing of brush.

In recent years, research and development on metal additive manufacturing technology has been active in various fields. One of the metal additive manufacturing technologies is wire arc additive manufacturing (WAAM). WAAM can be added to existing parts, and when combined with machining, has a high affinity for the manufacture of vanes and blades, which are important parts of turbomachinery. However, related research has been limited to the manufacturing of parts such as turbine blade or screw propeller and has not been able to verify the incorporation of the manufactured parts into turbomachinery. In this study, a fan type inducer made of stainless steel was developed using WAAM and machining. The developed inducer was assembled to a centrifugal pump, and pump performance tests were conducted to investigate the applicability of this manufacturing process to turbomachinery. The results of the study show that this process is industrially advantage.

In the maintenance of precision machines, regular cleaning is critical to the performance and service life of parts. However, with the remarkable improvements in manufacturing technology, the shapes of machine parts have become more complex such that more efficient cleaning technology is required. This study clarifies the effects of different shapes of machine parts on microbubble cleaning with surfactants and investigates efficient cleaning methods. In the previous study, experiments were conducted on flat specimens. In this study, in addition to flat specimens, three-dimensional specimens are prepared, and experiments are conducted. A cleaning solution containing a surfactant are filled with microbubbles and cleaning experiments are conducted. Experimental results between planar and three-dimensional specimens are then compared. Results showed that the cleaning effect of the three-dimensional specimens was worse than that of flat specimens on the microbubble cleaning process when certain surfactants were combined.

Cavitation erosion is a serious problem in turbomachinery. Quantitative prediction of the cavitation erosion by a numerical simulation is desired. The collapse of a bubble cloud attached to a solid surface causes high pressure and is the most destructive phenomenon. In the present study, a direct numerical simulation of the collapse of a bubble cloud was performed, where the mixture flow model with VOF method is employed, and AMR is used to capture the gas-liquid interface. The result of the collapse of a bubble cloud half attached to a wall showed that the outer bubbles deformed into a concave shape toward the center of the bubble cloud. The outer bubbles gradually collapsed toward the inner bubbles, and the bubble cloud finally collapsed, producing maximum pressure.

We verify applicability of a computational fluid dynamics (CFD) method based on a phase-field model (PFM) to direct numerical simulation of microscopic droplet motion on structured and heterogeneously wettable solid surfaces. Instead of the Cahn–Hilliard equation, the conservative Allen–Cahn (CAC) equation is adopted to calculate the advection and construction of diffusive interfaces. A numerical scheme based on the lattice Boltzmann model is employed to solve the Navier–Stokes equations of fluid coupled with the CAC equation in one-field formulation for an immiscible incompressible isothermal two-phase fluid system with equal densities and viscosities. Droplet motions under external force are simulated on grooved, square-pillar-arrayed, and flat sold surfaces in three dimensions. From the numerical results in qualitative comparison with available experimental data, it is confirmed that the PFM-CFD method can be used to simply evaluate the wettability of micro-fabricated solid surfaces with patterned 3D structures for efficient evaluation and optimal design by analysis of the functions of micro-fluidic devices in various fields of science and engineering.

Using microbubbles coated by a thin shell as Ultrasound Contrast Agents (UCAs) for ultrasound diagnosis improves image resolution. Since numerous microbubbles are used in clinical practice, understanding the acoustic properties of liquids containing multiple microbubbles is important. However, interactions between ultrasound and numerous coated microbubbles have not been fully investigated theoretically. Additionally, ultrasound contrast agents with shells made of various materials have been developed. Recently, Chabouh et al. proposed an equation of motion that considers the anisotropy of the shell [Chabouh et al., J. Acoust. Soc. Am., 149 (2021), 1240] and reported that the anisotropy of the shell affects the resonance of the oscillating bubbles. In this study, we derived a nonlinear wave equation describing ultrasound propagation in liquids containing numerous coated microbubbles based on the method of multiple scales by expanding Chabouh’s equation of motion for a single bubble. This was achieved by considering shell anisotropy in the volumetric average equation for the liquid and gas phases. The anisotropy of the shells was observed to affect the advection, nonlinearity, attenuation, and dispersion of the ultrasound waves. In particular, we have discovered an anisotropic case that suppresses attenuation and promotes nonlinearity.

Weakly nonlinear propagation in bubbly liquids is investigated theoretically and numerically mainly toward medical applications utilizing the combination of focused ultrasound and microbubbles. The Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation, that has been used as the mathematical model for the nonlinear propagation of focused ultrasound in single phase liquid, is extended for the liquid containing multiple microbubbles. The resultant KZK equation can consistently describe the nonlinear propagation of focused ultrasound, nonlinear oscillation of multiple bubbles and the thermal effects of gas inside the bubbles. Moreover, the resultant KZK equation is numerically solved and the intensive temperature rise is obtained near the focal point.