Control of flow separation on a vehicle front bumper model using a string-type dielectric barrier discharge plasma actuator (DBD-PA) was performed experimentally at Re = 56,000. The front bumper model composed of a side flat plate and a quarter cylinder with diameter of 169 mm was set up at 200 mm downstream from the exit of blowing-type wind tunnel. It was fixed with an aerodynamic sideslip angle of 10 degrees with respect to the main flow direction. Suction and blowing jets were induced in upstream of flow separation by the string-array type PAs. In x/R = 0.5 cross section, it was clarified that the displacement thickness was reduced by 47% by PA under the suction control in comparison with that under the blowing control, and suction jet had a higher control effect of flow separation than blowing one.

This paper presents experimental results of DFC (Delayed feedback control) of PSJA (Plasma Synthetic Jet Actuator) for LED cooling by induced flow. The dynamics from the duty ratio of driving voltage to the LED temperature is identified as a linear system. The state feedback gain for the optimal LQ tracking is by manually adjusting the gain calculated, we were able to achieve stable convergence to the target values. Experiment results show that the LED temperature converges to near target values.

To detect fires in the tunnel, fire sensors are installed according to the tunnel grade. And, in order to maintain the fire detection function, the detection lens must be cleaned so that the transmittance does not deteriorate. In some tunnels, there is an environment where soot and dust easily adhere, so there are fire sensors which cleaning is done more than the standard cycle. This time, in order to suppress the adhesion of soot and dust, we developed a duct to improve the flow velocity around the lens using CFD analysis, and we were able to suppress pollution by about 30%.

Water spray systems are installed on highway tunnels to prevent the increase of damages by vehicle fire accidents. The installation standards of tunnel emergency facilities including the water spray system are classified according to the tunnel rank. At the Takaosan Tunnel of the Ken-O Expressway, water spray system additional installation construction has become necessary due to the change of the tunnel rank. However, this construction period is long-term and traffic volume at the Takaosan Tunnel increased rapidly greater than the expected. It was supposed that the number of the traffic restrictions would be increased and it affects the customers and its safety. Therefore, we examined the lower positioning of the water spray system without the functional degradation to reduce the number of traffic restrictions.

In the safety evaluation of tunnel fires in Japan, a fire of one large bus is assumed, and ventilation control is performed to maintain the evacuation environment. Confirmation of maintaining the evacuation environment in the event of a large-scale fire accident has not yet been fully considered. In this study, the safety is evaluated by the number of evacuees exposed to smoke when the scale of the fire increases under the condition of zero flow control. In this way, we consider the effect of reducing the wind speed in a large-scale fire.

Taiwan Hsuehshan Tunnel fire investigation had revealed that the evacuation of the elderly took time more than twice as long as the young. Nowadays, the aging society is required to improve the transportation infrastructure. Even there are barrier-free city buses, but seldom barrier-free sightseeing buses, in fact. Therefore, in this study, we conducted the experiments that the subjects, who wore the elderly set, to get off the bus in a tunnel fire for the flow rate investigation. As a result, it was found that the flow rate count of the elderly is smaller than that of the younger group.

When a road tunnel fire, it is important to secure an evacuation environment for users by controlling the longitudinal wind velocity with ventilation equipment. Relatively old tunnels have a small internal cross-sectional area, which makes it difficult to control smoke and may require evacuation action in the smoke. In recent years, road tunnel fires have been studied to understand the diffusion of smoke and the evacuation environment, and experimental data on the amount of heat generated and smoke emission have been accumulated. However, data on the concentration of toxic gases contained in smoke are not enough understood.

In this report, we summarize and report on the relationship of CO and HCN concentrations with respect to the heat generation rate and smoke generation rate due to a light vehicle fire.

In the case of tunnel fires, it is speculated that the psychological factor of evacuees have influences on the evacuation behavior. Nonetheless, the relationship between the psychological factors and the evacuation behavior in tunnel fires has not been clarified. In this study, in order to clarify the impact of psychological stress on evacuation behavior in tunnel fires, we conducted evacuation experiments using a smoke tent, and investigated the heart rate, evacuation speed and blood pressure. As a result, there were 9 subjects’ heart rate increased during the experiment when Cs = 0.5 m^-1 and 0.9 m^-1 before the experiment. The mean heart rate ratio (during/before) of 9 subjects at Cs = 0.9 m^-1, was 0.02 larger than that of Cs = 0.5 m^-1. There were 6 subjects’ blood pressure increased after the experiment in the cases of Cs = 0.5 m^-1 and 0.9 m^-1. Due to blood pressure recovering characteristic after the experiments, there was a difference between the results by Omron and Wahoo Tickr. In all rising group such as the heart rate, systolic blood pressure and diastolic blood pressure at Cs = 0.5 m^-1 and 0.9 m^-1, the maximum evacuation speed was larger and the minimum evacuation speed was smaller than that of the decreasing group.

The authors conduct Fire Dynamics Simulator (FDS) simulation for tunnel fire on a single-track railway mountain tunnel with a small cross-sectional area. FDS gives calculation results of the arrival time, moving speed, and temperature rise of the hot gas. The heat transfer coefficient between the hot gas and the tunnel wall can be identified from the theoretical formula and the numerical simulation results. In addition, simple formulas for the arrival time, moving speed, and temperature rise with the distance from the fire source and the heat release rate can be also obtained.

Magatama blade has been proposed as a blade specialized for vertical axis wind turbine (VAWT). Cross section of the blade has been investigated by using Genetic Algorithm (GA) by authors to improve its performance. In this paper, performance of VAWT with the Magatama blade is experimentally investigated. As a first step, wind tunnel experiments are conducted with a small scale VAWT model at low tip speed ratio condition. Results show that power coefficient C_P of the improved Magatama blade increases at any tip speed ratio λ. Performance tests with large scale VAWT model are then conducted at open-air facility at relatively large tip speed ratio condition. In this field experiment the performance of the Magatama VAWT were compared with that of conventional VAWT with NACA0018 blade. Results show power coefficient C_P of the Magatama VAWTs are larger than that of conventional VAWT with NACA0018 blade.

In the wind farm, the wake velocity of the upstream wind turbine flows into the downstream wind turbine. In order to design more efficient layout of the wind farm, it is necessary to estimate more accurate velocity distribution of the turbine wake. The wake velocity, however, can be affected by the turbulent intensity of the inflow wind, due to turbulent diffusion of the momentum. Therefore, consideration of the inflow turbulence effects is imperative for the accurate estimation of the wake velocity. CFD is the most powerful tool for the wake analysis, however, its computational load sometimes becomes too heavy to obtain far wake velocity distribution. The present study proposes the calculation methods for the wake velocity of the wind turbine, by adopting panel method for the fluid analysis. For the consideration of the inflow turbulence, Veers model is used for the turbulence generation. The obtained calculation results are compared with the experimental results and the results from the engineering models, such as NEDO model, in order to evaluate the validity of the proposed method.

In this study, we investigate the flows around two Savonius turbines that rotate independently by numerical simulation considering the application to ocean current pawer generation. In general, when analyzing the flow around a rotating object, a rotational coordinate system is often used. However, it is difficult to calculate with such coordinate system when two objects rotate in the reverse direction independently. Therefore, we use the overset grid that consists of two rotational coordinates for each turbine immersed in a steady coordinate to calculate this turbines’ system. The basic equations are the incompressible Navier-Stokes equations expressed by the both rotational and stational coordinate systems. The nonlinear terms of the basic equations are approximated by the third order upwind difference in order to perform stable calculations even at high Reynolds number. The fractional step method is employed to solve the basic equations. In this study, two-dimensional simulation is performed by changing the direction of the mainstream, and the influence of interaction is investigated.

This study employs large-eddy simulations to investigate the effect wind farm layout on the flow fields and performance of offshore wind farm. To that end, four wind farm layouts (two aligned and two staggered) are defined over the fixed farm area. From the flow field analysis, it can be observed that wind speeds upstream of each turbine are relatively higher in staggered configuration due to larger streamwise spacing. Unlike aligned layouts what have high- and low-speed columns, staggered wind farms have relatively evenly distributed wind fields. Regarding the power output, fully staggered layout can generate 25% higher power than the aligned case with the same streamwise spacing.

Offshore wind farms are attracting attention as a measure against climate change because they are environmentally friendly and generate a large amount of electricity. However, as a problem of wind farms, it has been pointed out that the wake of the wind turbine reduces the amount of power generation and causes fatigue fracture. In this study, the yaw steering method was adopted as a solution to the wind turbine wake problem. The yaw steering method is a method that causes the wake deflection by tilting the rotor surface of the wind turbine that normally faces the inflow. By deflecting the wake, the influence of the wake on the downstream wind turbine can be suppressed. As a result, the power generation of the entire wind farm can be increased, and the service life can be extended. From the results of the wind tunnel experiment, it was confirmed that the wind turbine output increased under certain conditions. In addition, the results of numerical calculations revealed that the asymmetrical flow field on the left and right of the tower affects the flow velocity distribution of the wake.

In recent years, with the progress of technology, drones have become widespread. Drones are often used in situations where fixed movements are made in a wide space, such as spraying pesticides, surveying, and inspecting buildings. Another example of utilization is to mount an observation device on the drone and measure the wind speed, but the drone becomes larger. Therefore, in this study, the wind speed was measured using the flight data of the drone. By using the drone, wind speed can be measured easily and inexpensively. From the results of the wind tunnel experiment, it has become possible to obtain the wind speed from the flight data of the drone. In outdoor measurements, the wind speed obtained from the drone roughly matched the anemometer value. As a result of measuring the wind speed with drones before and behind the wind turbine, it was confirmed that the wake of the wind turbine was slower than the inflow. Through measurements in various environments, the effectiveness of wind speed measurement using the drone was confirmed.

The purpose of this research is to experimentally investigate how increase of the air inlet area of the engine cooling air affects the aerodynamic characteristics depending on the shape of the front-end of the vehicle body. A simplified 1/5 scale car model was used with reproduction of the engine compartment. In past researches, we used a rectangular front-end model, and in this research we used a round front-end model with a shape closer to the actual vehicle. In the wind-tunnel experiments, the moving-belt ground board were used to capture ground effects. The experiment was conducted at a wind speed and a moving belt speed of 20 m/s. As a result, the drag force of the round model was lower than that of the rectangular model, but the lift was not reduced.

In recent years, attention has been paid to the activity of Unmanned Aerial vehicles such as disaster site surveys and home delivery using drones. However, the current UAV cannot fly for a long time because of the influence of viscosity. The application of biomimetics is being considered to improve the performance of the UAVs. Dragonflies are known to have high flight performance among flying organisms, and the fine structure existing in the wings of dragonflies is considered to be important. There are some types that can fly over 7100 km by using gliding flight. In this paper, we focused on the micro spike of about 100 μm on the wing surface of the dragonfly and performed computational fluid dynamics on changes in spike density using ANSYS FLUENT. As a result, it was confirmed that the drag coefficient was reduced by increasing the spikes density. It is thought that this is because the flow velocity is reduced by the micro spikes, which suppresses the growth of the vortex and reduces the pressure difference. From the above, it was considered that the pressure drag was reduced by the micro spikes. This consideration could be confirmed from the analysis results.

The aerodynamic characteristics of several airfoils under constant-pitch-rate motions are experimentally investigated at a Reynolds number of 50000. The non-dimensional pitch rates are between 1.8×10^-5 and 2.8×10^-3. When the non-dimensional pitch rate is 9.0×10^-4 or less, every wing model shows quasi-steady characteristics. The influence of the pitching motion appears around stall conditions at the non-dimensional rates of 4.5×10^-4 and above. Moreover, NACA0012 and reversed NACA0012 airfoils show lift hysteresis between pitch-up and pitch-down motions when the angle of attack is low. The size of the hysteresis at low angles shows an airfoil geometry dependency. It is found that the aerodynamic hysteresis disappears in the case of NACA0004 airfoil. The effect of pitching motion appears at near-stall conditions even for NACA0004, although the change in the lift coefficient becomes small compared to the ones for the thicker wings.

Shredder paper is treated as industrial waste. In order to pack this cut paper in a plastic bag so that it could be effectively used as packing when shipping packages, a method was developed to take out the cut paper from a cylindrical container filled with the cut paper by controlling the flow rate. A spiral feeding device rotated around the horizontal axis at the bottom of the container, a disk rotated around the vertical axis at the center of the container, and a piano wire attached to the rotating disk stirred the cutting paper and supplied it to the spiral feeding device. The characteristics of the moment and the number of rotations required for rotating the both axes were investigated experimentally.

The effect of centrifugal force acting in a supersonic turbine used in a liquid rocket engine was studied. In past experiment and numerical simulation, a shock wave was created at the leading edge of the blade, and the Mach number in the passage between the blades had been reduced. In the present study, The entrance Mach number was 1.94, and the turning angle of the blades was 120°. It was found that centrifugal force created the shock wave at the leading edge, reducing both the Mach number and total pressure. This phenomenon is characteristic of high-speed blades with large turning angles. A convergent-divergent configuration of the passage between the blades suppresses the performance degradation of supersonic turbines.

The asymmetric gas bearing is a bearing developed to improve the maintainability of a large vibrator used for ground investigation. We also investigated the vibration characteristics of asymmetric gas bearings and ordinary symmetric gas bearings, and found that the vibration damping performance of asymmetric gas bearings is excellent at about 15 Hz or higher. For this reason, we will apply gas bearing technology to newly design and develop a rotary joint for transporting air, and evaluate its performance. First, a static levitation test was performed without rotation, and the theoretical value and the experimental value were compared. We found that they match quantitatively in the thrust direction and qualitatively in the radial direction. Then, the change in the number of revolutions due to the shaft diameter of the rotor was investigated, and the optimum diameter in the experimental equipment of this study was found. Next, numerical analysis was performed using the DFM (Divergence Formulation method). Here, we confirmed how the pressure distribution changes due to eccentricity.

Turbines are used in aeroengines and generators, and turbine blades generate power. In actual machine, the turbine is exposed to a harsh environment because the mainstream and the wake, which is generated at the trailing edge of the upstream blade inflow into the domain. The influence owing to the wake inflowing has been studied for a long time. And we have revealed that the wake inflowing make the separation bubble short. Although it is important to study how the wake inflowing affect the flow field, it has never been understood clearly. The reason is that the wake inflowing not only affect the shape loss but accumulate as the loss at the flow domain. We need to investigate the wake mixing loss isolation from whole cascade loss. In this study, we separate wake mixing loss from cascade loss by using Denton Loss and new method. Besides, we study the relationship between the loss and the shape of the domain by estimating the wake deformation.

The diffuser rotating stall is one of the biggest problems in pumps because unstable flow and pressure fluctuations are induced and the pump operating range is severely limited. However, it is difficult to quickly predict the flow rate at the onset of diffuser rotating stall. Unsteady-state analysis is generally used to investigate the internal flow of the pump in detail for rotating stall, but the computational cost is huge and the design process is inefficient. In this study, we investigated a simple prediction method using steady-state analysis by CFD. We focused on the deviation of the mass flow rate between diffuser passages near the onset flow rate because the precursor to the onset of rotating stall is non-axisymmetric flow. The validity of the method was verified by comparing the analysis results using the simplified prediction method with the experimental results.

A potential way to reduce cooling system noises generated by heavy construction machinery is to generate the required cooling airflow with a low fan speed, and one way to accomplish this is to optimize the ventilation path through which the airflow generated by the cooling fan passes. The computational fluid dynamics (CFD) approach would be effective for modeling the three-dimensional pressure drop characteristic of such systems. However there have been few reports aimed at clarifying the loss generation mechanisms or suggesting minimization methods based on flow field viewpoints. Accordingly, in this study, we visualize the three-dimensional (3D) flow field characteristics of an electric cooling fan system installed within the cooling enclosure of a heavy construction machinery and investigate the details of the system’s pressure drop mechanisms. The total pressure drop that occurs in the exhaust side enclosure accounts for 26% of the total pressure drop that occurs in the entire enclosure. In the exhaust side enclosure, the pressure drop is increased because the shape of the exhaust port is not corresponded to annular flow of the cooling fan wake.

In this study, large eddy simulation (LES) for turbulent flows through several isosceles triangle ducts with different top angles is performed using immersed boundary (IB) method. As results of mean quantities, the streamwise velocity is the smallest in the case of regular triangle duct and increases as the top angle increases. The mean secondary flow in the cross section becomes strong at the small top angle. The turbulence energy and Reynolds stress disappear near the corner of the small acute angle. From the visualization instantaneous field, it is shown that no low-speed streak and no vortex structure appear near small acute-angle conners.

We report on the experiments of turbulent pipe flow with a porous wall. The pipe wall consists of a cylindrical porous medium in which there are many radial fine through-holes connected with a plenum chamber. We have investigated the dependence of friction factor f on Reynolds number Re up to Re~10⁵ in porous pipe flow with a chamber, porous pipe flow without a chamber, and a smooth pipe flow. In the non-porous case, turbulent flow exhibits the Blasius law f = 0.3164Re^-1/4 in the range of 3 × 10³ ≲ Re ≲ 10⁵. In porous pipe flow with chamber, on the other hand, we have found the scaling f~Re⁰ at higher Re ≳ 2 × 10⁴, implying the Taylor dissipation law. In porous pipe flow without chamber, the friction drag increases compared to the non-porous case, but f decreases with increasing Re at Re ≲ 10⁵. The significant difference in porous pipe flows with and without chamber suggests that the scaling f~Re⁰ in porous pipe flow with chamber is attributed to the fluid motion through the porous wall.

We have performed experiments of turbulent thermal convection in cylindrical container of aspect ratio D/H = 1, bounded by the two (heated or cooled) horizontal porous walls, where D and H are the diameter and the height of the container, respectively. The horizontal walls consist of porous media of the thickness L = H, in which there are many through-holes of diameter d ≈ 0.05H, connected with plenum chambers underneath and overhead. At the low Rayleigh number Ra ≲ 4 × 10⁷, the Nusselt number Nu is comparable with that in turbulent Rayleigh−Bénard convection between impermeable (closed porous) walls, but as Ra increases, the wall permeability leads to significant heat transfer enhancement. At higher Ra ≳ 2 × 10⁸, we have found the scaling Nu~Ra^1/2 implying the ultimate heat transfer. The visualization of the temperature field using encapsulated the thermochromic liquid crystals has shown that strong large-scale thermal plumes, quite distinct from small-scale plumes observed in the non-porous case, appear in the ultimate state.

The effects of turbulence intensity on the aerodynamic characteristics of wing models at a Reynolds number of 3.6×10⁴ are investigated in a wind tunnel. The aerodynamic characteristics of a two-dimensional wing and a low-aspect-ratio wing are compared. The low-aspect-ratio wing has an aspect ratio of 1.0. The NACA0012 airfoil was used in both models. A sudden decrease of the lift coefficient disappears at the stall, when the turbulence intensity exceeds a certain level. However, for the two-dimensional wing with TI ≧ 8.1%, the decrease in the lift coefficient at the stall is not clearly observed. The stall angles increase with increasing turbulence intensities for the two-dimensional wing, but it was approximately constant for the low-aspect-ratio wing. In both cases, it is found that as the turbulence intensity increases, the effect of turbulence intensity on the lift slope becomes small. The maximum lift coefficient is found to increase with increasing turbulence intensities for the two-dimensional wing, but gradually decrease for the low-aspect-ratio wing. Thus, there are qualitative trend differences between the two-dimensional and low-aspect-ratio wings in terms of the effects of turbulence intensity on the aerodynamic characteristics.

Cold spray (CS) is one of the thermal spraying methods which make coatings by spraying melted minute particles on substrate surfaces. Solid particles are sprayed onto a substrate at high speed to form a coating accelerated by a supersonic gas flow using a convergent-divergent nozzle. Therefore, it is important to understand the gas flow condition inside the nozzle that accelerated the gas flow. However, diagnosing internal gas flow is almost impossible for commercial CS nozzles because the nozzle is fabricated with hard metal alloy to prevent abrasions of the nozzle. Therefore, it is impractical to drill pressure taps to the CS nozzle to diagnose the gas flow. To solve this problem, authors propose non-intrusive flow-diagnostic methods which uses outer surface temperature of the CS nozzle and temperature recovery factor of the working gas. This research shows that the accuracy of this method is improved by measuring the outer surface temperature of the entire axial direction of the nozzle, and that the temperature recovery factor of the internal flow depends on the stagnation pressure. Therefore, the temperature recovery factor of the internal flow should be treated as a function of stagnation pressure.

For a baffled vessel agitated by conventional disk turbine impellers with six flat blades, the liquid flows discharged by the impellers were measured using the particle tracking velocimetry (PTV) for the turbulent flows to be evaluated. The PTV measurements were comparable to those by the lasser Doppler velocimetry which has been often employed over other techniques for flow measurement. The geometry of the impeller and vessel having baffles was suggested to affect the turbulent flow level in the impeller discharge flow.

The agitator providing forward-reverse rotation whose rate changes periodically in the sinusoidal pattern employed an impeller with the disk turbine impeller with 12 flat blades, for turbulent agitation of liquid. The liquid flow discharged by the impeller was measured using the particle tracking velocimetry (PTV) and was compared with that with the conventional turbine type impeller with 6 flat blades. For the 12 flat blade impeller, an efficacy to rectify the flow was demonstrated as a decreased level of the turbulent flow relative to the mean flow.

At the Great East Japan Earthquake in 2011, various structures along the coast were damaged by tsunami. Therefore, methods for evaluating tsunami damage to structures came under extensive review. The causes of tsunami damage can be classified into two types, one is wave force, and the other is debris collision. We focused on added mass effect related to debris collision. The added mass effect is generated by motion in water. In order to clarify the effect of added mass at the time of collision, we developed simulation models for added mass effect using CFD analysis. Experimental tests corresponding to the CFD analysis of underwater collision were performed for validation. By using this model, we performed simulations of debris collision after horizontal floating to determine an added mass coefficient. We confirmed that the definition of prior knowledge about added mass effect is useful even in collisions, which are typically high-acceleration phenomena. Furthermore, we formulated an approximation of the added mass coefficient of floating debris.

This paper aims to investigate flows in a model of microscopic lymphatic vessels of mice for developing noninvasive cancer treatments. The model consists of an axisymmetric tube with its diameter changing linearly along the axis, called a tapered tube. Reynolds number of the flow is assumed to be much smaller than unity because the tube diameter and the flow velocity are small. Continuity equation and Navier-Stokes equations are solved in an analytical manner based on the Stokes approximation. Solutions of the velocity and pressure are represented in nondimensional forms. The friction coefficient of the flow is expressed in a simple form for convenience of applications.

Jet with Re ≪ 1 is observed downstream of valves in lymphatic vessels of mice and it is an impending research target in developing treatment of noninvasive cancer, especially breast cancer. The jet has the characteristic that the pressure and velocity greatly vary at the exit because of flows with angle change of ninety degree at the exit periphery. A new theory of Stokesian free jet is presented as a model of the jet from a lymphatic valve to predict the pressure in the jet region. Navier-Stokes equations and continuity equation, expressed by the spherical coordinates, are solved under the Stokes approximation by taking radial pressure and velocity variations at the exit into account. Flow field is divided into two regions by the hemisphere with its origin at the exit center and the exit radius, inner region and outer one. The former is inside the hemisphere and the latter is outside it. The pressures in both regions are given by Legendre polynomials, multiplied by powers of the radial distance, and the velocity components are expanded by two series of unknown functions of the angle, multiplied by the powers of the distance. The pressure gradient and the stream lines in the outer-region solutions are patched with those in the inner-region one over the hemisphere, resulting in reasonable solutions in forms of infinite series for the pressures and the velocities. Numerical examples show nonuniformities of the exit pressure and velocities.

In this paper, the aggregation of microbubbles by ultrasonic irradiation is attempted. The effect of ultrasonic frequency on the area of captured aggregates and the diameter of formed bubbles were investigated. The microbubbles are generated in a polydiaperse (1~100μm) by the porous material in the water tank. The microbubble group was irradiated with ultrasonic waves of three different frequencies (26,78,130kHz) in order to investigate the influence of the frequency of ultrasonic waves. The resonance diameter of the microbubble was changed by changing the frequency of ultrasonic wave. As a result, aggregate is formed from microbubbles by ultrasonic irradiation. The microbubbles which are smaller than a resonance diameter captured at the antinodes of the ultrasonic wave and the microbubbles which are bigger than a resonance diameter captured at the nodes of the ultrasonic wave. It was shown that the area of the aggregate increases as the frequency of ultrasonic wave increases. It was possible to control the diameter of the bubbles formed aggregates.

In this paper control of oil droplet in O/W (Oil-in-Water) emulsion (EM) stream is attempted. These oil droplets are positively and negatively charged by the cationic and anionic surfactants, respectively. The behavior is controlled by applying an electric field to the EM charged with a surfactant. The experiment is carried out in a flow path that branches in two directions. EM flow in this flow path. Iron plates are set on the side of flow path. Iron plates are connected to constant voltage power supply. EM is applied an electric field. An electric field is applied from the side walls of flow path. Oil droplets are guided to one branch. An electric field strength is controlled by the applied voltage. The applied voltage is increased. Oil droplets move to the electrode. Oil droplets are passed through one branch. Oil droplets are changed the direction of branches by type of surfactants.

A numerical scheme to analyze oscillations of a conductive droplet under DC magnetic fields in zero gravity was developed, and the effect of DC magnetic fields on the oscillation of a conductive droplet is investigated. In the present scheme, the Navier-Stokes equations for the liquid-gas two-phase fluid flow are solved by a Galerkin finite element method and the ALE method is used to allow a conductive droplet to oscillate. An elliptical conductive droplet is placed in the center of a two-dimensional rectangular domain and uniform DC magnetic fields are applied in the x direction. It is confirmed that the DC magnetic fields generate Lorentz force in the directions which prevent oscillations of the conductive droplet, resulting in a damping effect of the oscillations. Furthermore, as compared with the case without applying a DC magnetic field, phase delay and phase advance are observed as a result of applying DC magnetic fields.

Diffusion characteristics of the turbulent jet can be controlled by modifying the initial condition, namely the nozzle shapes. Lobed jet is one of the non-circular jets, supplied from the nozzles with wave-shaped edges. In this study, we measured the self-similarity of the velocity fields of two lobed jets with six lobe peaks but different curvatures (6L and 6S), and compared their diffusion characteristics with those of a round jet. The results show that the mean streamwise velocity distribution display the self-similarity in x/De≳5 and the RMS value of fluctuating velocity x/De≳20 for all of the investigated jets. Therefore, we conclude that the self-similarity region of the present flow fields is x/De≳20. The flow rate of the lobed jet is lower in the self-similar state than that of the round jet. In contrast, the difference of the flow rate between the two lobed jets is small, proposing that the diffusion characteristics of the lobed jet is almost independent of the curvature of the nozzle shape.

An evaporative cooling system using ultrasonic vibrators has been proposed for the small centrifugal compressors in the micro gas turbine system, in order to decrease the compression work. The validity of the cooling system had been verified experimentally for the certain compressor. In order to clarify the extent of the validity of the system, a numerical analysis model is being constructed for the cooling system, which can be applied for various types of compressors. The present model simulates the evaporative cooling in the mist introducing duct, implying the physics of the advection and the diffusion of the mist, the vapor, the heat and the momentum of the air flow, as well as the evaporation. The present paper shows the effects of vortex generator (VG) installed in the mist introducing duct, through the measurements of the temperature decrease and the advection velocity distribution in the duct. The installed VGs produce strong secondary flow, which advects the water mist even to the upper region of the duct, resulting in the promotion of the evaporation and the decrease in the air temperature of the duct.

Although many recent studies about the cavitation effects on the atomization of sprays, few studies have taken the viscosity effect into account. Therefore, we investigated how the development of cavitation and its atomizing effect on spraying depend on the difference in viscosity. In the present study, glycerin-water solution adjusted to three different viscosities was used as the fluid sample. Cavitation in the nozzle and spraying were visualized with the metal halide lamp installed at the back of the nozzle and recorded using a high-speed camera. Results showed that cavitation is less likely to occur as the viscosity increases. Furthermore, the flow structure in the nozzle was visualized by the shadowgraph method, and the relationship between the vortex and cavitation was discussed. As the viscosity increases, development of cavitation needs large injection pressure and flow velocity. It can be thought that the pressure drop in the condensing area and the local pressure drop due to the vortex become smaller as the mainstream velocity decreases.

Since ships are exposed to severe corrosive and fouling environments, the coating of hulls is an important factor in determining the life of ships. However, in most cases, the details of hull coating operations are not managed, and basic information for production management, such as the amount of paint used and working hours, is not available. In this study, we investigated a simple method to measure such basic information on painting work. We investigated a method for monitoring the amount of paint used and working hours based on the operating principle of an airless coating machine used in shipbuilding.

Abrasive-water suspension jets (ASJs) which jet out the suspension mixed water and abrasive in advance are excellent even at relatively low pressure. Although ASJs system by bypass system is advantageous in terms of equipment maintenance and cost as the jetting time increases the abrasive concentration in the vessel decreases, since high pressure water directly flows into the vessel and pushes out the suspension. In this study, we aim to stabilize the abrasive concentration by the bypass system which has a merit in terms of cost and simple structure and perform highly accurate cuttings. The stabilization of the abrasive concentration was adjusted by changing the opening of the valve attached in the bypass pipeline and changing the flow rate over time. The change in the flow rate was made based on the equation derived from the equation by formulating the change in the abrasive concentration in the suspension vessel by the differential equation. We conducted a cutting experiment using a 0.3 mm thick aluminum plate under stable abrasive concentration conditions.As a results, although the cut width decreased without stabilization adjustment, when the valve opening was adjusted, the cutting width became almost stable.

A hemispheric head cyclone separator has higher collection perfoemance of fine particles compareing with a conventional cyclone separator with a cylindrical head. In order to optimaize the shape model with hemispharic head, we have investigated the air flow in various shape cyclone models by making numerical and experimantal approaches. In the near future, we will propose the compact cylone with hemisperical head for use as an intake side pre-filter for fuel cell vehicles. In this study, we forcus a dust holder which requrires the most large space to achieve space-saving of an installation space in vehicles. The internal air flow characteristics in hemispheric head cyclone separators with dust holder variously down sized has investigated by direct numerical simulation (DNS). Using the average air velocity field of numerical results, the translational motion of particles is analyzed by the Lagrangian Particle Tracking (LPT) method. The particle collection coefficiendy at particle density of 1000 kg/m3 is shown. As a result, it is found that the downsizing of the dust holder causes a decrease in the collection coefficency of particles smaller than 2 μm. The downsized dust holder require that the air flow easily flows into the dust folder and the inside air is sufficiently stagnant.

A base oil with a high viscosity index (VI) over the entire operating temperature range is preferred for the engine. Improvement in viscosity at high temperature can be achieved by adding a viscosity index improver (VII) polymer. However, it is important to understand the interactions between the oil and the immersed polymers for optimum design criteria of the VII polymers. The current study aims to understand these interactions from a macroscopic perspective by using a highly accurate and coupled numerical model of lattice Boltzmann method and Brownian dynamics method.

It is required to reduce both the friction and lubricant oil consumption (LOC) in order to reduce CO₂. In addition, as the requirement to reduce particle number(PN) may be realized by reducing LOC, the relationship between LOC and PN should be examined. Elucidation of the mechanism of LOC is a basic and applied field and a common subject, however, only the LOC is measured by the weight method etc. and the mechanism is not clarified so far. Thereby, the relationship between LOC and PN was measured in a wide operation area in a production engine in this study.

In this study, formation and evaporation of liquid fuel film on various walls were investigated. Iso-octane was injected from multi-hole injector of GDI engine. Injected spray impinged to an aluminum wall having different surface roughness (R_a = 1.07 μm to 17.1 μm) and fuel film was formed. Wall surface temperature before fuel spray impingement was controlled by an electric heater (25°C to 130°C). Fuel film formation under various conditions were captured by high-speed camera. Fuel film area changes and evaporation lifetime of the fuel film were measured from captured top view image. As a result, lifetime of the fuel film became shorter with an increase of surface area of the wall.

With the motivation to optimize the cost and time of function development and calibration of the ECU, reinforcement learning (RL) technique, DDPG (Deep Deterministic Policy Gradient) has been applied to coordinated control of gasoline ICE air-system/combustion system manager. As an environment part of the RL system, surrogate ICE model using deep learning technique, simulates resembled real driving situation and it is coupled with ECU model including steady-state setpoints maps and intervention by RL-actions.

In this paper, training either using the real driving pattern or the synthetic driving pattern is compared. It was observed that synthetic pattern based on statistical analysis of real driving data helped reduction of the training steps by 1/3. At the end, the controller policy provided by the well-trained actor is analyzed from the automotive ICE expert’s point of view and concluded as reasonable strategy has been obtained through the reinforcement learning.

The authors have studied an argon closed-cycle hydrogen engine in regard to system configuration, starting and fueling methods, thermal efficiency and losses, the effect of water vapor in the working gas, and the effect of argon concentration. Argon concentration is a trade-off between increased thermal efficiency and worsened knocking, and no method has been found to balance the two. Since the closed-cycle engine recirculates all the exhaust gas except water, the ratio of oxygen, hydrogen, and argon can be set freely. In this study, the oxygen/hydrogen mixing ratio was extended to the extreme range to investigate the possible operating range. The compression ratio and argon concentration were also varied to investigate the effects on knocking and thermal efficiency.

In this study, the ignition delay time of gasoline blended with various hydrocarbons having different molecular structures (isooctane, n-heptane, 1-pentene, and toluene) was measured using a rapid compression machine. Additionally, the effect of mixing hydrocarbons on the ignition characteristics of gasoline surrogate fuels was investigated. The ignition delay times were measured under two conditions: an equivalence ratio of 0.5 and an equivalence ratio of 1.0 with an EGR ratio of 30%. The compressed pressure and temperature were 4.0 MPa and 750 K, respectively. When toluene was blended with the gasoline surrogate, the ignition delay time increased regardless of the experimental conditions. In contrast, when n-heptane was blended with the gasoline surrogate, the ignition delay time decreased. When isooctane and 1-pentene were individually blended with the gasoline surrogate, the ignition delay times were unchanged with varying mixing ratios. Based on the chemical kinetic analysis, it is found that the reactivity for the low-temperature oxidation of blended fuels changed when each hydrocarbon was blended, which determines the ignition characteristics of blended fuels.

A temperature measurement method based on laser absorption spectroscopy was developed to obtain the time history of temperatures during the low-temperature oxidation (LTO) of iso-octane. The absorption signals of H2O were measured using two near-infrared distributed feedback laser diodes emitting at wavelengths near 1392 and 1842 nm. The temperature was obtained based on the absorbance ratios between two temperature-dependent absorption lines. The temperature profiles in the LTO of iso-octane at 0.77 MPa, 660 K were successfully obtained. The calculated temperature profiles using the latest chemical kinetic model of iso-octane had the same tendency as the experimental profiles.