Three-dimensional numerical simulation of high pressure hydrogen jet is performed. Hydrogen leakage from the high pressure hydrogen tank has a possibility of serious explosion accidents. Therefore, it is necessary to understand diffusion behavior and ignition characteristics of hydrogen leakage. The present study simulates the high-pressure hydrogen supersonic free jet into the atmosphere to understand the dispersion process. As a result, the Jet flow fluctuates greatly in the radial direction and hydrogen disperses in a wide sphere. Also, lambda vortex structure was found to perform a crucial function in the diffusion of hydrogen.

In this study, the flow characteristics of transonic and supersonic under expanded air free jets issued from orifice nozzle are examined experimentally by flow visualization using Schlieren method, measurements of velocity distribution by a supersonic Pitot-tube. These jets are used widely, for example, as a driving flow of ejector. The difference between the flow characteristics of pipe jet issued from a circular nozzle and orifice jet is made clear and the effects of contraction area ratio of orifice nozzle are also examined.

The three-dimensional compressible Navier-Stokes equations are numerically solved to study suppress Mach wave emission in a supersonic round jet at high Mach number using high-order compact upwind schemes. Two cases of inlet disturbance for Mach number M_j=2.0 are presented. The first case is the jet flow forced randomly. The second case is the jet forced by random disturbances and a pair of unstable 3rd helical modes (m=±3) with a subsonic phase speed. The numerical results show that the jet potential core region is reduced in the jet forced by a pair of 3rd helical modes. Therefore, the intense Mach wave radiation observed in the randomly forced jet can be reduced by forcing with a pair of 3rd helical modes.

An application of ultrasonic acoustic resonance to piezo-driven synthetic jet pumps is examined both experimentally and numerically. Tested are acoustic resonances between two parallel disks (distance between disks << their radii), one of which has an orifice at the center and the other is driven by the piezo actuator into its resonant vibration in the axial direction. It is confirmed that significant increase of pressure amplitude is realized by the acoustic resonance and the flow rate amplitude through orifice has its extremum there. The flow rate amplitude depends on the orifice diameter and the distance between disks, and they have their optimum values to give the maximum flow rate amplitude. We conclude that the acoustic resonance is useful to enhance the performance of piezo-driven synthetic jet pumps.

In this study, coaxial type DBD plasma actuator was designed for jet flow diffusion control. DBD plasma actuator mounted on the tip of the converging nozzle and gives the induced flow on the boundary layer flow. DBD plasma actuator was driven by burst-mode and studied diffusion of jet. We applied peak-to-peak voltage 14kV to DBD-PA at time of Reynolds number 1000, 2000, 4000, 5000. The wave form used sin wave and square wave with all Reynolds number. As a result a section becoming f_vortex > f_burst, f_vortex = f_burst, f_vortex < f_burst exists in x/d=1(f_vortex:vortex development frequency, f_burst:burst frequency, x/d:the distance of the plumb direction from the nozzle exit / Nozzle diameter). When f_burst is low, it becomes f_vortex>f_burst and becomes f_vortex < f_burst when f_burst is high.

In order to elucidate the jet diffusion mechanism by coaxial DBD plasma actuator, the plasma induced flow was measured by a hot wire anemometer, were analyzed. By changing the duty ratio, it was show a change in the three velocity fluctuation distribution. In duty = 10%, the shear layer was provided a periodic disturbance. In duty = 50%, it became the pulsating jet. In duty = 90%, it was a continuous shear layer. It was examine the fluctuation strength and periodicity of the plasma induced flow, due to change in the duty ratio.

A plasma actuator has been widely studied as an active flow control device. We have developed a micro plasma actuator, which has small electrodes of 1 millimeter or less in size, for installing in small machinery. The wavy micro plasma actuator has induced streamwise vortices, enhancing the momentum mixing between mainstream and boundary layer. Additionally, we have developed the multistage type wavy micro plasma actuators so as to generate stronger streamwise vortices than those induced by single one. For evaluating the effect on separation control, we have performed PIV measurement of flow around NACA0012 airfoil at low Reynolds number. PIV results have presented that both micro plasma actuators have suppressed separation region.

To reveal the oscillation mechanism of a flip-flop-jet nozzle with a connecting tube, the authors assume that the jet switches when a time integral reaches a certain value. As the time integral, we consider the accumulated flow work of pressure, namely, the time integral of mass flux through a connecting tube into the jet-reattaching wall from the opposite jet-un-reattaching wall¹⁾. In the present study, in order to discuss the physics of the accumulated flow work further, we conduct the experiment in single-port control where the inflow from the control port on the jet-reattaching wall is forcedly controlled and the other control port on the opposite jet-un-reattaching wall is sealed, instead of the experiment in regular jet's oscillation using the ordinary nozzle with two control ports in connection. As a result, the accumulated flow work of the inflow until the jet's switching well agrees with that in regular jet's oscillation using the ordinary nozzle.

Effects of DC voltage for the flow control performance using tri-electrode (TED) plasma actuators was analyzed in wind-tunnel experiments. The jet from TED actuator is increased (DBD) or changed direction (SD) compared with the jet of SDBD plasma actuator. In low speed wind-tunnel tests of separation control on the NACA0012 airfoil at Reynolds number at 6.0×10⁵, the plasma actuator was mounted on the leading edge of the airfoil. The experimental results show that the TED actuator has advantage in the flow control performance compared to the SDBD plasma actuator. On the other hand TED-DBD and TED-SD do not have many difference.

Measurement of flow induced by ceramic plate Dielectric Barrier Discharge (DBD) Plasma Actuator (PA) is conducted by using 2D2C particle image velocimetry in the windless situation. Velocity distribution in the streamwise direction and the wall-normal direction and the maximum induced flow of PA are calculated by using image processing. Effects of the applied frequency and the applied voltage on the maximum induced velocity of PA are investigated. The induced flow is widely observed along the wall and a sink flow also observed on the electrode. The effect of frequency on the maximum induced velocity is small, while the effect of voltage on the maximum induced velocity is large. The maximum induced velocity of the ceramic PA is confirmed up to approximately 1.4 m/s.

This study shows the results of experiments in which the delayed feedback control at a flow velocity of a cylinder wake using PSJA. PSJA is a fluid control device using plasma generated by dielectric barrier discharge. The aim of this experiment is to effectively suppress the generation of vortices at the rear of a cylinder by the delayed feedback control method. The experiments are performed at Re = 1.6×10⁴ . The delayed feedback control was converted into PWM signals for the external input to the drive circuit output obtained from the hot wire anemometer in the microcomputer, and drive PSJA. As a result, the PWM driving by the delayed feedback control relative to non-driving, an increase in the flow velocity, a reduction in the turbulence intensity was seen. However, this result is not extend to the result of the continuous driving, it did not lead to effective suppression of vortex. Therefore, it is necessary to review threshold during PWM signal conversion in microcomputer and optimize the delay time τ.

This paper deals with separation flow control over an NACA0015 airfoil using a nanosecond-pulse-driven dielectric-barrier-discharge plasma actuator (NSDBD-PA). In this study, we evaluated the effects of driven frequency of NSDBD-PA on aerodynamic forces and associated flow field at the free-stream velocity of 40 m/s (Reynolds number of 252,000) by conducting force measurement and Particle Imaging Velocimetry (PIV) measurement. The results of force measurement show that the effective value of non-dimensional frequency (F⁺) are different at the post-stall angle (α = 22 deg) and the deep-stall angle (α = 28 deg). The results of PIV measurement show that, at F⁺ = 0.25 and α = 28 deg, the vortices generated by NSDBD-PA are combined with the ones from the lower surface and from large-scale vortex structure travelling downstream. It is inferred that vortices pass over the upper surface of the airfoil, resulting in, an increase in lift and drag.

A Synthetic jet device is a tool for generating a jet, and a useful tool for active flow control. Synthetic Jet actuators are low operating power, zero-net-mass-flux and very compact devices. Therefore, a synthetic jet is expected as a new method of boundary layer control. The orifice shape is an important parameter, which have an effect for boundary layer control. However, the effect of non-circular synthetic jets for boundary layer control is unknown. The purpose of this study is to investigate the effect of orifice shape for boundary layer control. In this experiment, circular orifice and two rectangular orifices were used. For the rectangular orifices with long side set in the spanwise direction, the boundary layer mixing is promoted and makes effective the separation control.

In recent years, graphene oxide suspension has been attracting attention, because of its high thermal conductivity and high lubricity characteristics. The purpose of this study is to determine the characteristics of the pipe flow of graphene oxide suspensions experimentally. Experiments were carried out using a stainless steel pipe with an inner diameter of 2 mm. Graphene oxide in the form of monolayer sheets of 0.8 nm thickness was used in this study. Sheets of two sizes were used: 3 μm and 300 nm. The concentration of suspension is 0.1 wt%. The results of the study showed that the viscosity of graphene oxide suspensions can be regarded as equivalent to that of Newtonian fluids, and the viscosity of graphene oxide suspensions increases with increasing particle size. The friction coefficient of graphene oxide suspensions is the same as that of distilled water in the laminar flow range. In the turbulent flow region, the friction coefficient of graphene oxide suspensions decreases slightly compared to that of distilled water.

In this study, drag reduction by additives in a turbulent pipe flow has been studied. Experiments were carried out using a head tank to prevent mechanical degradation, and the friction loss was evaluated from the flow rate. As a result, it was found that aqueous solutions of organic additives and suspensions of them showed high drag reduction. Drag reduction by suspensions of organic additives is as same as that by aqueous solutions, and the drag reduction by suspensions may be caused by that fibrous material. It is also found that the conductivity of the solution is not always proportional to the drag reduction rate.

Pressure drops were measured with constant flow rates because flow properties of dilute aqueous solutions of polymers passing through capillaries, which diameter ranged from 125 μm to 680 μm, were investigated. Good agreement between the resultant pressure drops for water and the predicted ones for laminar flow and Blasius expression was obtained even though small-sized capillaries were used. On the other hand, laminar flows were maintained in transition region by using dilute polymer solutions. Pseudo-laminarization of dilute polymer solution was thus obtained. Furthermore, we discussed relationship between the phenomena and their elastic properties.

Recently, there are many studies about pipe friction loss because almost energy loss with fluid transportation is ruled in pipe friction at very long fluid circuit such as oil pipeline, water and sewage and so on. There are many methods used to reduce pipe friction loss but there are problems. Therefore, we focused on Microbubbles (MB) MB which has various characteristics such as reducing pipe friction loss, self-pressurizing and so on. On the other hands, MB becomes small with time and disappear in water so we have to provide MB in the middle flow channel to get the effect reducing pipe friction loss. The purpose of this paper is measured pipe friction loss when generated MB by using orifice plate and injected air and flow characteristics. As a result, pipe friction loss decreased when orifice plate is set. Also, the reduction rate of pipe friction loss is decrease when the Re increased. Also, we confirmed bubbles are collapsed when a pipe was injected air but its diameter was bigger than theoretical diameter.

Processes of the air entrapment in microstructures fabricated on walls of rectangular microchannels were visualized by a high-speed camera. Effects of the geometry of the microstructures on the formation and the shape of the liquid–gas interface in the microstructures were investigated with four channels having the same dimensions but different microstructure geometries at Re = 1. The microchannels were made of stainless steel and acrylic, and the microstructures were hydrophobized by triazinethiol. Water–ethanol mixtures with different mixing rate (ranged from 0:100 to 100:0) were employed as the test liquids, thereby effects of the wettability on the liquid–gas interface formation process could be investigated as well. Consequently, four types of the interface behaviors were observed. In addition, observing the flow of the liquid–gas interface area, to investigate the effect of the liquid–gas interface has on the flow.

We apply the suboptimal control theory to a flow around a square cylinder to investigate its control effect. The cost function is chosen to be the pressure drag. The control input is assumed to be continuous blowing and suction on the cylinder wall. The control law is derived so as to minimize the cost function under the constraint of linearized NavierStokes equation. With this control input, the mean drag coefficient is found to reduce by 6.6% at most. Vortex shedding from the cylinder is also suppressed to result in reduction of the lift fluctuations.

A square cylinder is typical shape of a building and the bridge beam, therefore the grasp of its aerodynamic characteristics is important for the wind-resistance design. However, the study does not advance in comparison with many cylinders and is insufficient to grasp those. It is clarified that the pressure from wind decreases by changing the shape of the square cylinder from the study of Tamura and others. We focus the shape of the square cylinders with the step. The purpose of this study is to clarify the influence that steps gives in aerodynamic characteristics. The number of steps is changed and the drag measurement experiment using the wind tunnel and the visualization experiment using the water tunnel is made.

Recently, many studies have discussed the characteristics of flow around a circular cylinder, for especially shape modification and drag coefficient. In this paper, the two-dimensional aerodynamic flow characteristics around a circular cylinder are investigated. Cylinders with various groove depth are used. The drag coefficient is measured with a wind tunnel test. From the results, it is clarified that the separation point of the horizontal section of the circular cylinder moves to downstream and the drag coefficient decrease, as groove become deeper. It is found that the drag coefficient with groove decreased by about 28.6% in compared without groove.

We have previously confirmed that a Goerlter vortex occurred in the circumferential direction in the boundary layer of the rotary cylinder put in a uniform flow. The aim of this study is to confirm the separation position on the rotating cylinder changed by some grooves along the circumferential and the span direction in a rotary cylinder. We visualized the separation position the Goerlter vortex that was a whirlpool long in PIV measurement experiment measurement experiment. It was confirmed to be changed by the depth of the ditch which is dug in a cylinder, or with/without grooves. Furthermore, we confirmed it about the outbreak of the Goerlter vortex and relations of the detachment.

The objective of the present study is to elucidate the drag reduction mechanism by the suboptimal control for turbulent friction drag reduction by conducting the resolvent analysis. In the analysis, the turbulent velocity field is expressed as a linear superposition of propagating modes, identified via a gain-based decomposition of the Navier-Stokes equations. This decomposition enables targeted analyses of the effects of control on coherent turbulent structures such as the near-wall cycle (NW-modes) and very-large-scale motions (VLSMs). In the present study, we investigate the effect of suboptimal control on these turbulent structures.

Influences of pressure gradient on the friction drag reduction effect of uniform blowing or suction in a turbulent boundary layer is investigated by means of Reynolds-Averaged Navier-Stokes simulation. In the present study, to create an adverse-to-favorable pressure gradient, a suction-blowing velocity distribution is prescribed along the upper boundary. As a result, drag reduction effect of uniform blowing is increased by adverse pressure gradient and suppressed by favorable pressure gradient. On the other hand, it is also found that pressure gradient has a little influence on the overwall change in skin friction.

The effectiveness of LEBU for drag reduction in rough wall turbulent boundary layers has been examined experimentally. LEBU was located at two different heights, 0.4δ and 0.8δ and local wall shear stress was measured by drag balance device. The mean velocity and Reynolds shear stress profiles were measured by constant temperature anemometers. It is confirmed that LEBU is effective for drag reduction in rough wall boundary layers. The reduction rate of local skin friction coefficient in the rough wall flow is larger than that over smooth surface. Reynolds shear stress measurements state that LEBU reduces momentum transfer due to turbulent motion produced by interaction between boundary layer flow and roughness elements.

In this study, we conducted PIV measurements for a turbulent boundary layer with nonionic surfactant solution injection from wall surfactant at the momentum thickness Reynolds number up to 1500. The nonionic surfactant, which mainly consists of oleyldimenthylamineoxide (ODMAO), was used. Turbulence structures were investigated for water and surfactant injection flows.

The prediction of the turbulent flow of a viscoelastic fluid is required for engineering applications. We applied a Reynolds stress model proposed (for Newtonian fluid) by Hanjalic & Jakirlic (1998). This model can predict a turbulent flow in a Newtonian fluid with precision. In the viscoelastic turbulence, we should model an additional nonlinear term of fluctuating strain and conformation tensor in the ensemble-averaged constitutive equation. In the present model of the nonlinear term, we investigated the model parameters in order to adjust them to the adopted background Reynolds stress model aiming at a better prediction of the mean velocity profile. The present model can predict mean velocity profile better than earlier model by Leighton et al. (2003). The optimal values of model parameters were found to depend on either the friction Reynolds number or Weissenberg number. The relationships between the model parameters and flow parameters are formulated. Moreover, we tried introducing a viscoelastic pressure strain term, since the anisotropy of the Reynolds normal stress is significant character in the drag-reducing flow.

Friction loss on the flow passages accounts for about half of all losses of the hydraulic turbine. In the performance enhancement of the hydraulic turbine, the reduction of the shape loss has been performed mainly. However, it is more necessary to reduce friction loss to improve efficiency. The present paper deals with experimental investigation using two kinds of surface-treated material coated on a flat plate fixed in the rectangular channel in order to observe effective skin-friction reduction. As the results it was seen that the organic hydrophilic coating decrease the skin-friction drag. Consequently it was confirmed that in the model test the turbine efficiency improved within a certain Reynolds number by the runner applied an organic hydrophilic coating to blade surfaces.

In this investigation the effect of relaminarization was confirmed by periodic pulsation flow using the Gas Transport Pipe.The effect of relaminarization obtained during acceleration period was confirmed by calculating the turbulent intensity and flow velocity distribution from the local flow velocity measured by the Hot wire anemometers.

An experiment is performed to investigate the drag-reduction effect in a turbulent channel flow on a traveling wave wall. The wall is made of a thin rubber sheet vibrating to generate a traveling wave. The rubber sheet was vertically placed at the middle of the channel. A piezoelectric actuator is used as a vibrating source. A vibration experiment with the input frequency of 120Hz is investigated to check whether or not to occur a traveling wave. Since the phase velocity does not become within the range of effective parameter for drag reduction, the pressure-drop difference between uncontrolled and controlled cases cannot be confirmed.

The effect of streamwise wave-like wall deformation of a turbulent channel is studied through direct numerical simulations. Here, the simulation was conducted under constant pressure gradient, unlike past studies, which was held under constant flow rate conditions, in order to prevent friction velocity changes before and after the control for concrete discussions on mechanism of drag reduction. Simulations reveal that wall deformation grants approximately 40% drag reduction, due to random component of velocity fluctuation drop and negative periodic Reynolds shear stress.

We have synthesized a low-molecular-mass organogelator: cyclohexane carboxamido (HPMDA-R), which is composed of four amide groups with two kinds of side chains (R and R'). These chains have different alkyl groups: 2-ethylhexyl (2C₈) and oleyl, which are effective to increase solubility and the formation of the structure by self-assembly after the dissolution. In this study, we evaluated rheological properties of HPMDA-2C₈/oleyl for paraffin oil and ester oils. From the results, HPMDA-2C₈/oleyl contributed to increase the viscosity and viscoelasticity of isododecane, while to give gelation state for isostearyl isostearate.

In recent years, the development of microfabrication technology has encouraged the research of microscale flow. However, the detail of the non-Newtonian fluid flowing through the microchannel is not insufficient yet. The purpose of the present study is to clarify the behavior of non-Newtonian fluid flow through the microchannel, we carried out experiments to obtain the velocity profiles in the microchannel with an abrupt contraction. In addition, we have focus on the secondary flow upstream of the abrupt contraction where the characteristic flow of the non-Newton fluid can been observed conspicuously. Thus, we measured vortex lengths occurring in the abrupt contraction. As the result, we have clarified that the electric interaction between the wall of the microchannel and the fluid affects the velocity and the vortex lengths near the wall.

Effect of concentration on flow induced orientational changes of Xanthan gum solutions in a planar channel with an abrupt expansion were examined by measurement of the flow induced birefringence and velocity fields along the centerline. Five kinds of solutions with different concentrations (0.4, 0.45, 0.5, 0.7, 0.9 wt%) were tested in this experiments and relaxation times were evaluated from the G' and G'' curves respectively. Temporal decreases in birefringence were observed just after the abrupt expansion due to the elongational effect. Moreover, longer birefringence changes were observed as the concentration became higher in the downstream regions where the influence of shear was dominant. There was a good relationship between the birefringence changes and the Weissenberg numbers estimated with the relaxation times. From these results, it is clarified that flow induced alignment structure of the polymers after the abrupt expansion was strongly affected by the elongational flow field and the relaxation properties of the polymeric liquids.

Velocity-volume data of sedimenting rigid spheres in viscoelastic liquids were experimentally obtained. The flow fields around a sphere were also measured by using a particle image velocimetry (PIV). No discontinuity in terminal velocity was observed. However, there was a discontinuity in the rate of change of terminal velocity with volume at a shear-wave-based sphere Mach number of unity. It was found that the formation of Mach cones around a sphere plays a key role in the sedimenting velocity of the rigid spheres.

We observed 2D flow birefringence profile near a vertical flat walls of an upside-down air tight quartz cell filled with CTAB/NaSal aqueous solution. When a tiny bubble is placed inside the top wall of the cell, an oscillating flow can be generated by pressing a rubber film at the bottom of the cell by a sinusoidal vibrating piston whose vibrating amplitude, frequency and center positon of the cell can be tuned precisely. As the bubble is getting contracting and expanding alternately, shear waves were observed clearly, which was propagated from the vertical wall using the 2D high speed polarization camera. In this study, a correlation of the propagated waves and propagation speed of the shear waves were studied and discussed experimentally.

Rheological behavior of interstitial fluid in epidermal tissue, including blood micro-circulation, can vary skin mechanics in micro scale, i.e. visco-elasticity. Therefore, an in vivo diagnosis of blood velocity is quite necessary to diagnose skin tissue. In this paper, we propose OCDV (Optical Coherence Doppler Velocigraphy), which is a method of tomographic micro-visualizing blood flow velocity based on a high frequency modulated low coherence interferometer. The rapid scanning optical delay line was implemented as a reference arm so as to visualize video-rate tomography of velocity field. This system applied experimentally to RBCs suspension (Hct40%) pressurized into a simplified capillary vessel of rectangular PDMS microchannel. Consequently, this could offer tomographic velocity in micro circulation, as an in vivo tomographic diagnosing tool of blood flow velocity profiles in tissue.

Static mixers are simple devices for mixing fluids capable of saving space and energy in comparison with stirring tank systems. Many static mixers have developed and commercialized, while a new static mixer; MSE (Multi-Stacked Elements) static mixer has also developed in our previous work. Inadequate mixing conditions are frequently observed for complex fluids; however, it is difficult to evaluate the non-uniformity of mixed fluids. In this study, we have conducted flow visualization using a green laser sheet device and a high speed video camera to evaluate mixing performance for static mixers including MSE static mixer. Experimental study was conducted using viscous and/or poor compatible fluids to propose five indexes, which can express the ability of static mixers.

An interesting phenomenon about irreversible viscosity in the large amplitude oscillatory shear, LAOS, of the wormlike micellar solutions is found. A wormlike micellar solution exhibits a different viscosity in the CW direction compared with one in the CCW direction in each period of the LAOS flow. This phenomenon appears only when a suitable preshear is applied before the LAOS flow. The difference of the shear stress between the CW direction and the CCW direction at a several periods from the onset of the LAOS is very large and it is named the transient irreversibility. In some condition, the irreversibility keeps permanently. It is named the permanent irreversibility. The transient irreversibility becomes large in a certain shear rate in the pre-shear, but the permanent irreversibility is not affected by the shear rate of the pre-shear.

In this study, we investigated mixing patterns of paddle impellers with two large blades in shear-thinning fluid by decoloring experiment and visualizing streak line. As a results, isolation mixing region like doughnut ring was observed in the upper side of MAXBLEND and Super-mix. On the other hand, that was observed in the center part of FULLZONE. By increasing Reynolds number, isolation mixing region like doughnut ring was quickly diminished. Streak line of MAXBLEND is also changed according to Reynolds number. Mixing patterns are changed according to Reynolds number, and mixing is improved by increasing Reynolds number.

Addition of a little amount of high-molecular-weight polymers in a Newtonian fluid reduces turbulent intensity, which causes the drag reduction in a pipe flow. When the drag reduction occurs in a flow, vortices generated in the flow deform. In this study, in order to understand the vortex formation and vortex deformation in turbulent flows affected by extensional rheological properties of polymer solution, we have observed the vortices in two-dimensional turbulence. Polyethylene oxide and hydroxypropylcellulose were used as polymers that have different extensional rheological properties. We investigated how the relaxation time of the polymer solution that is related to the extensional viscosity of the solution affected the vortex shedding in two-dimensional flow.

To develop the amorphous liquid crystalline actuators which can drive objects as well as can change own shape, the behavior of a liquid crystal droplet under electric fields has been investigated. In this work, two kinds of electric fields are employed, and they are (1) a lateral electric field and (2) vertical electric field. For the case of the lateral electric field, the liquid crystal droplet moves until its gravity center reach the center of the paired electrodes. On the other hand, for the vertical electric field, the droplet continue moving until the field is turned off. Also, the flow in the droplet is visualized by tracking the micro-particles mixed in the liquid crystal.

It is one of challenging problems to remove well dispersed fine particles from dilute slurry, because filtration and evaporation process requires a lot of time and energy. Electrophoresis is known as a method to enhance sedimentation of fine particles with isoelectric point electrophoresis on a substrate. We use the electrophoresis technique for fine particles with higher zeta potential to make concentrated paste of fine particles near electrodes. Concentrated paste near the electrode is falling down during electrophoresis process, finally drops from the electrode. We examined a process to collect the concentrated particle as a paste. In this study, we successfully visualized transport phenomena of fine particles in slurry under electric field using micro X-ray CT.

In this study, in order to realize the high efficiency of the filling process of milk without large-scale splashes of milk, we focus on the effect of the in-flow condition at the nozzle where the milk is injected on the filling process. We assume two in-flow conditions which are flat and sine-curve velocity profiles and computationally reproduce the flow dynamics of milk filling process for two in-flow conditions. In the case of the flat profile, much air is entrained in the milk and many bubbles are generated in the carton. Accordingly, it is shown that the disturbances of the free-surface shape attributable to bubbles bursting at the gas-liquid interface became larger than that for the sine-curve velocity profile.

In this paper, we carried out experiments on backward-facing step (BFS) turbulent flow to investigate viscoelastic influence. We performed particle image velocimetry (PIV) measurement on turbulent flow passing BFS for Newtonian and viscoelastic fluids. The measurement fields were set in x-y plane and x-z plane (here, x is streamwise direction, y is wall-normal direction and z is spanwise direction). The instantaneous velocity fields show that meandering main flow in x-y plane (not in x-z plane) on certain conditions. We employed analysis to investigate characteristics of turbulent structure using of method combined with 4-quadrant classification method and two-point correlation function. The results show that meandering motion is dominated varicose mode, vortices are generated from shear layer, accompanied with that low speed fluid ejecting from upper wall. High correlation region of streamwise velocity fluctuation corresponding to meandering motion is observed at inflection point of streamwise velocity.

It is important to investigate two-phase flow phenomena in tube bundles. In this study, difference of instantaneous and time-average void fractions in in-line and staggered tube bundles at pitch-to-diameter ratio of 1.5 were investigated. Void fraction distributions around tubes across horizontal tube bundle in liquid-gas two-phase flow were measured using X-ray radiography. It was confirmed that time-dependency of void fraction was more apparent in intermittent flow. Time-average void fraction distribution was high at front of a tube and low at back of a tube in bubbly and intermittent flows in the staggered bundles. Time-average void fraction at the maximum gap was higher than that around the other points at intermittent condition in in-line bundles. Volume-average void fraction in in-line tube bundle was approximately 20% higher than that in staggered bundle. Further, it was confirmed that volume-average void fraction at higher mass flux could be predicted by the Feenstra's equation.

This paper proposes a digital holographic particle measurement using multi-wavelength holograms for improvement performance in particle measurement. In reconstruction of digital holography, 0th and ±1st order diffracted light waves occur. The 1st order diffracted light wave forms the shape of recorded object, while other two light waves cause noises in reconstructed images. The proposed method reduces the influence of the 0th and -1st order diffracted light waves on the quality of reconstructed images. Further, by using a color camera for capturing digital holograms, it becomes possible to simultaneously record a set of holograms with different wavelengths for adapting digital holographic measurement to dynamic phenomena. Therefore we evaluate the performance of the proposed method in numerical simulation by varying the wavelength of reference light wave. It is shown that the measurement accuracy is improved by the proposed method using multi-wavelength holograms.

A method of visualization for the flow containing microbubbles is presented. The aim of the visualization is to investigate how microbubbles stay inside a turbulent boundary layer of a vertical flat wall as main flow passes by horizontally. A color coded volumetric illumination using a computer-controlled liquid crystal screen projector successfully extract three dimensional distribution of microbubbles close to the wall. From the result, long survive of microbubbles within low-speed streak regions and intermittent bursting of microbubble clouds due to ejection events have been clearly visualized, which contribute to the first-principle understanding of microbubble drag reduction,

PVA (Polyvinyl acetal) brushes have been widely used for a wet cleaning in semiconductor device fabrication. To better understanding the lubrication condition between a PVA brush and cleaning surfaces, we observed gas-liquid-solid interface using a total reflection microscope with polarization plates. First we investigated the real contact area of a POM (Polyoxymethylene) ball by applying a normal load in air and water. Then we observed the contact condition of a PVA brush. As a result, the observed real contact areas of the POM ball were agreed with the estimation from the Hertzian contact theory. In addition, the real contact area between a PVA brush and a glass plate in water was also able to observe. The real contact areas were increased with increase the normal force acting on the PVA brush. We concluded that the part of a PVA brush is contact with a cleaning surface.

Centrifuges have important part in solid-liquid separation process of sewage plant to reduce slurry. Measuring solid-liquid separation phenomena in centrifuge is required to obtain more effective separation and save energy. However, the measurement device that measures solid-liquid separation phenomena in centrifuges has not existed yet, because centrifuges rotate at high speed. Therefore, in this study the measurement device with wireless communication function for centrifuges has developed. The measurement device is composed of constant current circuit, voltage measurement circuit, wireless communication device and electrodes. The measurement device measures solid-liquid separation phenomena(particle sedimentation thickness) by measuring electrical resistance between electrodes. Experiments carried out attaching the measurement device on centrifuges. The changes of particle sedimentation thickness were measured changing elapsed time and feed rate. Particle sedimentation thickness increased with the passage of time and increases of feed rate.