Effectiveness of a micro jet on the flow control has been investigated experimentally for a stronger wall jet. A small tap on the wall for self-preserving development region generates the micro jet and suction for the turbulent wall jet. Flow rate of the jet/suction is limited smaller than 1/100 overall flow rate in the shear layer of the wall jet. Velocity measurement was made with constant temperature anemometers and single or crossed hot-wires. Integral of the streamwise momentum flux with respect to the whole layer was calculated to confirm effectiveness for the flow control. The micro jet increases mean velocity and integral of the streamwise momentum flux. However, suction has almost no influence on the mean velocity profile and the momentum integral.

Effect of favorable pressure gradient on the similarity in the turbulent boundary layer has been investigated experimentally. In an equilibrium turbulent boundary layer under favorable pressure gradient, mean velocity, Reynolds stresses and wall shear stress were measured and compared with similarities as seen in flat plate boundary layers. The logarithmic mean velocity profile holds in the inner layer under the favorable pressure gradient. Otherwise, the wake component in the outer layer disappears due to the favorable pressure gradient. Turbulent kinematic energy budget is evaluated and compared for zero and favorable pressure gradients. The production and dissipation are almost balanced in the inner layer under zero and favorable pressure gradients. However, the production, dissipation and diffusion terms are reduced in magnitude under favorable pressure gradient. In the intermittency of the turbulent-nonturbulent interface, turbulent region seems to be enlarged due to favorable pressure gradient.

A series of direct simulations of a fully-developed turbulent flow over a mesh-screen type permeable plate whose geometrical property is systematically changed is performed to identify the relationship between the wall pore structure and the flow characteristics in a wall-bounded turbulent flow. The flow resistance is found to be increased by increasing the porosity of the plate or by decreasing the pore size, and to be closely associated with the blowing/suction intensity through the pores. However, there exists a certain critical pore size, below which the flow resistance is decreased by decreasing the pore size, and the flow goes back to the classical impermeable channel ow. It physically means that, below the critical pore size, the pore is too small for fluid to go through it freely.

A numerical study has been conducted to examine turbulent flow and heat transfer characteristics in a three-dimensional square-duct with V-shaped ribs. The computations are based on RANS and LES models. Water is the working fluid with the flow rate of which Reynolds numbers equals to 18500. The computation reveals that two symmetrical fully developed helical flow and developed heat transfer profile are generated. Effects of different rib shape on thermal characteristics for a ribbed duct flow are investigated. The change of the shape leads to increase in heat transfer and pressure loss. The velocity profile in the vicinity of ribs and streamline has been investigated, indicates that the different flow structures generated by the rib shape leads to superior heat transfer performance. Vortices are visualized, which indicates the connection between the heat transfer and flow structure

Direct numerical simulations are performed in plane Poiseuille flows with point-particles for varying density ratio of particle to fluid, or Stokes number. The purpose of our study is to understand subcritical transition in particle-laden flows. We investigated the effect of particle-fluid interactions on the robustness of intermittent localized turbulence, so-called turbulent stripe, in two-way coupling simulations. The stripe was found to disappear due to heavier particles with a density ratio over 4000, while it sustained with light particles, or small Stokes number. The particle-fluid interactions act favorably near the walls, but adversely in the channel central region with respect to the streamwise direction for all cases. The interaction force significantly is exerted in the case of heavier particle, or large Stokes number. In this paper, we also showed the instantaneous momentum transfer of the streamwise Reynolds normal stress. The production term gradually decreases with the increasing Stokes number. Furthermore, we found that the energy exchange due to particle-fluid interactions is from particle to fluid near the wall and is reversed in the channel central region. For larger-Stokes-number particles, the transports occur actively at each height during laminarization process.

In this study, we investigated the wall model for large eddy simulation by using flat plate boundary layer flow simulation. We conducted flow simulation by using different grid resolution, to find out the effect of grid resolution. We showed that the lack of resolution near the wall is affected to the overestimation of the production of kinetic energy. In addition to do simulation, we calculated the correlation between WRLES’s instantaneous flow and model’s result to evaluate the accuracy of the wall modeled LES by using spalding law as model. We found that there is no correlation between WRLES’s data and spalding law’s result.

We examine two datasets of high-Reynolds-number turbulent boundary layers. One is a new dataset obtained by direct numerical simulations on the K computer, and the other is a dataset examined in our previous studies. By using these two datasets, we investigate the shape and sustaining mechanism of the largest-scale vortices in turbulent boundary layers. For this purpose, we identify the largest-scale structures by a coarse-graining method. First, visualizations in physical space show that vortices as large as the boundary layer thickness are hairpin-like. This explains the disappearance of smaller-scale hairpin vortices as the Reynolds number increases. Second, to quantitatively show the dominance of hairpin vortices at the largest scale, we take an average, conditioned by the existence of the low-speed structures at the height of the boundary layer thickness, of the second invariant of the coarse-grained velocity gradient tensor. This simple procedure, indeed, reveals a (largest-scale) hairpin vortex. It is also verified that a low-speed structure is located between the legs of the hairpin vortex.

Turbulent heat transfer in plane Couette-Poiseuille flows has been investigated numerically at Reynolds number Re = 2000 for Prandtl Number Pr=1. In this flow system the lower wall moves at a temporally constant speed U_lower, while the upper wall is at rest. While keeping a volume flux (and so a bulk mean velocity u_b) constant, the lower wall speed is changed in the range of 0 ≤ U_lower/u_b ≤ 2 to establish turbulent Couette-Poiseuille flows. Dissimilarity between heat and momentum transfer is found significantly for a certain value of U_lower, for which the mean velocity gradient on the lower wall is weak enough to be free from vigorous turbulence activity. Only spanwise vortices exist in the near region of the quiescent lower wall to induce the streamwise velocity so that the wall velocity gradient may be weaker, leading to the excess of the wall temperature gradient (or heat flux) over the wall velocity gradient (or skin friction).

We have investigated the condition developing a small disturbance introduced in boundary layer. From result obtained, it had cleared that the wavenumber of velocity fluctuation in undeveloped spot converged near upper branch of the linear stability theory, and that of developing spot converged near lower branch. It indicates that the development of spot related to spacing of the hairpin vortex in the spot. Since its result was obtained for a specific Reynolds number, we need to investigate widely for various Reynolds number. Therefore, the purpose of this study was to clarify the relationship between development of spot and wavenumber of velocity fluctuation in spot for various Reynolds number. From result obtained, it was cleared that the development of spot can be arranged by the wavenumber evaluated from first spacing between hairpin vortices. However, it is necessary to consider that which part of spot should evaluate the wavenumber.

Plant gets the good function with the shape of body to survive. In the desert, the cactus needs to realize the saving water in a body and the evaporation of water for the growing. We examined the characteristics shape of cactus and what kind of water absorption network in the stem. We observed the surface of cactus using Scanning Electron Microscope (SEM). Root is similar with other plants. Spines are consisted long spines and short spines. Long spines are shaped like a bundled thin tube and have like a barb. Cactus has stoma on epidermis of the stem for the water absorption. Cactus has no leaf but cactus complement function. The result for path of absorbed in cactus shows that vascular bundle was divided into two when the body is branching. Observed from cross section, conduit extends along the side of stem. One of conduit branches for spines. Spines are connected with conduit. The dye flow visualization shows that the cactus has the mesh-patterned network in a stem. From the graph theory, the network of cactus for water absorption is closely connected and it is consist of nodes with similar function.

The purpose of this study is the development of an elastic sensor for measuring wall shear stress induced by flow water. We used a flexible sensor by MCF Rubber. MCF is the abbreviation for magnetic compound fluid. MCF Rubber is composed of NR-latex, nickel powder, and magnetic fluid. These materials are mixed, then polymerized with electric heat. The MCF Rubber can measure the force normal to rubber sensor and the shearing force acting on the rubber since the MCF rubber is conductive rubber. The magnitude of the force measured with the change of electric conductivity of MCF Rubber. The change of electric conductivity causes when the deformation of rubber by some time force acting on the MCF rubber. For the consideration of shear stress measurement with MCF Rubber, we used mechanism of a rotational viscometer. Rotational viscometer consists with a rotor rotates by a motor, and the rotor makes a flow in circular container. The wall shear stress can be changed with a rotational velocity of rotor. The strength of wall shear stress can be defined as σ=3τ/2πR³ on Japanese Industrial Standard (JIS). Here, τ is the torque acting on the motor shaft, and R is the radius of rotor. So, the torque converter is installed between the motor and rotor to measure the torque. Six type rotational velocity ranging from 100 to 600 revolution per minute (rpm) to understand the characteristics of MCF Rubber sensor for the wall shear stress measurement. The result shows that the MCF Rubber can measure the change of wall shear stress under the unsteady flow condition.

ABSTRACT The purpose of this study is the development of a training system for improving technical skills of canoe slalom athletes. One of the most important technique in the canoe slalom competition is the selection of optimal line between the gates. We are trying to visualize the path line of canoe to understand the difference from the optimal line. As the first step to develop the training system, we understand the characteristics of self-position estimation using BLE beacon. The results show the beacon needs to keep the distance less than 1m.

The small insect, especially the Diptera (for example, fly, mosquito and so on) has a pair of wing and can fly with high mobility and high efficiency. Hence, by consulting the flapping flight of Diptera, it will develop the small flight device which has high flight performance. We focused the planer shape of wing. Then the rectangular wing model whose aspect ratio is agree with that of Diptera wing was treated as the standard model and create some wing model. To study the aerodynamic feature, we performed the numerical simulation of flow around flapping wing by using ANSYS CFX. Then the behavior of the wing model was treated as the immersed boundary by using the “Immersed Solid” function. As results, the following became clear. The average lift force during half stroke is proportional to the squared flapping frequency and the wing area. When the two rectangular wings which have the same wing area were compared the average lift force, the long span wing is higher than the long cord wing. Comparing the mosquito like wing model (Real0) and the rectangle wing (Rect0) which has same cord and span with the Real0, the average Lift and thrust forces per wing area during half stroke were almost same value when the attachment angle of wing model was changed 0 to 60 degrees. Hence, the Real0 has more efficient than the Rect0 from the viewpoint of the generated force per unit area.

Swallowing disorder has been becoming a serious issue with increasing in elderly people. Disorder sometimes appears with a decrease in saliva, because saliva has an important role in lubrication over the oral cavity and throat. Though the structure of biological mucosa has been studied physiologically, there are only few studies that examined the influence of its micro structure on fluid lubrication. Therefore, we investigated the friction characteristics by reproducing the micro structure of oral cavity and pharynx. As an example of the oral cavity mucous membrane, the tongue of a pig was subjected to observation by microscope and laser surface shape and roughness measuring machine. As a result, roughness properties of a pig tongue differed from root part to tip part, and it was confirmed that hemispherical protrusions were observed on the tip part by irregular arrangement. An imitation tongue was produced using a high-precision 3D printer. Furthermore, the concentration of thickener was determined from the measurement of the viscous characteristic by the rotational viscometer to have the same viscosity as that of saliva. It is necessary to evaluate the rheological properties of mucus with low viscosity and high spinnability like saliva, and the viscosity characteristics different from the shear viscosity. Therefore, we investigated the rheological characteristics by measuring the extensional viscosity to make a mucus that simulates saliva.We measured friction force on the imitation tongue lubricated by artificial saliva. The friction force were changed depending on the lubrication condition and the moving speed.

Urinary stones are calcium oxalate stones in the urinary tract. According to the 2005 national survey, the lifetime prevalence of urinary stones is 15.1% for Japanese men and 6.8% for women. In addition, 96% of the whole are upper urinary tract stones such as kidney stones. Small stones are excreted in the urine without feeling great pain in the process of excreting, but when they become large, natural excretory becomes difficult and it causes severe pain when it descends into a narrow ureter. Therefore, it is desirable to establish a treatment that can be discharged before growing. However, the mechanism of the flow around kidney stones from the upper urinary tract has not been fully investigated, and confirmation by follow-up observation is also difficult. Furthermore, the natural excretion can be difficult from the lower kidney calix because of the gravity. We analyzed flows around a stone by numerical simulation using immersed boundary method. First, the numerical results and the actual experiment were compared with the free fall sphere. As a result, accuracy of the numerical simulation was confirmed. Furthermore, the lower kidney calix model was created based on medical computed tomography images, and the flow of stones was analyzed by numerical simulation.

Connector-tube interface is where very easily to occur thrombus formation in extracorporeal blood circulating system. For early detection of thrombus formation at the connector-tube interface, connector sensor was developed (by incorporating sensing electrodes on the connector). The aim of this study is to improve the electrode shape of the connector sensor for quantitative evaluation of thrombus. In this study, three types of electrode shapes were devised and evaluated using finite element method (FEM) simulation. The measurement area of each electrode was found from the current density distribution image. Also, simulations were performed with various types of thrombus, and the relationship between the thrombus volume and the change in permittivity was compared to clarify the electrode performance. From these simulations, it was found that the type of connector sensor using two arc-shaped electrodes is most suitable for thrombus quantitative evaluation.

We have developed a novel microporous covered stent (MCS) for the endovascular embolization treatment of intracranial aneurysm (IA). This stent promotes progressive thrombosis by flow divertion and facilitates IA embolization treatment by clotting of whole blood in the IA. However, difference of geometric configuration of each aneurysms affects the performance. In this study, we investigated intra-aneurysmal flow with various aneurysm position at a curved parent vessel by using in-vitro flow simulator. The IA models were placed at the outer-sidewall at the U-bend parent vessel, of which curvature was as same as that of human carotid siphon. The IA opening position on U-bend vessel was located at θ_a = 30, 60, 90, 120, 150 and 180 deg. Reynolds number of the parent vessel flow was set at 190 - 970 to simulate CCA blood flow. Microporous sheet (pore diameter: 100μm, aperture ratio: 30%) was placed as a model of a MCS at opening of IA. Flow velocity field at the IA model were measured by PIV. As the results, by MCS stenting, volumetric mean share rate (VMSR) in IA model became about 15 times smaller than before stenting. Dimensionless VMSR was increased proportionally by dimensionless IA in-coming/out-going flow rate increasing. These results suggest that our developed MCS has one of the best embolization device for IA therapy and is expected high embolic effects due to obstruction of direction flow in aneurysm.

The osmotic resistance of human erythrocytes under the hypotonic condition is studied. We experimentally observed the swelling and hemolytic behavior of a human erythrocyte caused by a hypotonic solution. The volume change by swelling was approximately estimated from the two-dimensional images of the erythrocyte during the experiments. The results show that the erythrocytes swell until getting spherical shape, and they tend to be reduced in volume and finally hemolyzed. Based on the light absorption characteristics, the mass of the hemoglobin included in an erythrocyte was estimated. Although the hemoglobin mass in an erythrocyte does not change immediately after the hypotonic solution was added, it starts to decrease at a certain time, indicating that the hemoglobin starts to leach out of the erythrocytes due to the hemolysis. The onset time would coincide with the time at which the erythrocyte volume starts to decrease. It is found that the hemoglobin leaching would begin after the erythrocyte getting spherical and it would cause the volume decrease. Additionally, we have attempted to visualize the hemoglobin concentration both in and out of the erythrocyte. The time-dependent concentration change was captured.

The usefulness of deep ocean water has been recognized in various fields such as food, agricultural and marine resources and medicine in recent years. Currently, there are two methods of taking deep sea water: the offshore type, which takes water from offshore bases such as ships and buoys, and the onshore type, which takes water by extending a pipe from the land. They are sucked up by the difference between the pressure at the pipe inlet and the water pressure in the pipe. In addition, the development of an efficient in-pipe water transportation system is considered to contribute not only to the intake of deep ocean water but also to the recovery of seabed sludge and water-soluble resources. The purpose of this study is to investigate numerically the effect of using a water jet from a nozzle installed in the middle of a pipe of a water intake device using a water pressure difference.

Shock absorbers are devices that reduce the vibration of the vehicle by the resistance of the internal fluid and improve the ride center and handling. Low damping force is preferred to improve ride comfort, but the opposite is necessary for maneuverability, and reciprocity occurs to improve both. To solve this problem, there is a method to adjust the damping force by changing the face century of the orifice. We focus on shock absorbers with fan-shaped channels as damping force adjustable shock absorbers. By using CFD as an evaluation method of this type, performance evaluation including the effect of vortices is performed.

The effect of expansion ratio and Reynolds number on a backward-facing step flow is investigated experimentally. The expansion ratio ER is changed to 1.5, 1.75 and 2.0. The Reynolds number Re based on the mean velocity and the hydraulic diameter of inlet channel ranges from 1.5 × 10³ to 6.0 × 10³. This Reynolds number range includes laminar, transition and turbulent flows. The wall static pressure and the forward flow fraction are measured. When the position of reattachment point is nondimensionalized by the step height, it moves to the upstream direction as the ER increases in the laminar region. However, it is almost the same in the turbulent region. The pressure loss due to channel expansion increases as the ER and Re increase.

With the global awareness of the environmental protection, regulations related to exhaust emission from an automobile is strengthened and enhanced. Because the turbocharger can make up for the displacement volume being decreased by downsizing engine, it is considered to be effective device for the improvement of the fuel consumption and the reduction of carbon dioxide. The turbocharger is used in the wide range from a low rotational speed to a high rotational speed. However, the appearance of shock wave in the compressor causes some problems in high rotational speed. A purpose of this study is to clarify the effects of the generation of shock wave on the flow field in the compressor. The pressure near the tip of blade of compressor is measured at different rotational speeds of impellers and these pressure histories are compared with each other. In this study, the performance test facility of the turbocharger with a combustor is used. The hot air compressed by a compressor is heated by the combustor and is used as the driving source of the turbine. The total inflow to the turbine is adjusted by a control valve, and the rotational speed of the impeller is set to 120000 rpm to 140000 rpm. As a result, when the rotational speed of the impeller increases, the mean pressure near the tip of blade decreases, and the scale of the pressure change increased. When a circumferential speed of the impeller reaches the transonic speed, the pattern of pressure change is distorted in the process of pressure increase.

When the temperature of automobile exhaust gas is low, the catalyst becomes inactive and this phenomenon is one of causes of environmental pollution. This study focuses on the pulsating flow in the exhaust pipe of the internal engine for heating up the catalyst and causing its activation. The flow through the exhaust pipe of the engine is modeled as the air flow which is pulsated by a rotary valve in test pipe and the relation between the wave phenomena and the fluid temperature is examined in this study. The change with time of the opening area of the valve is designed to be same as that of the exhaust port of an actual engine and an obstacle simulating a catalyst is installed in the test pipe. As test pipes, a straight pipe, a rectangular pipe, and two types of semiellipse pipes are used in this study, and pressure and temperature are measured using pressure transducers and thermocouples at some points in pipe. As a result, when the pulsation frequency is high, the pressure waves are found to merge into the shock wave upstream of the obstacle in the cases of all four types of test pipes, and the shock becomes relatively strong in the straight pipe. Furthermore, it is found that the fluid temperature most increases at the location where the shock wave grows and becomes strongest. In addition, when a semiellipse pipe is used, high pressure and high temperature is obtained at the focal point of the ellipse.

The micro-tube heat exchanger efficiently exchanges heat by flowing fluid into the flow path and small diameter tube. In recent years, thanks to 3D printers, it has become possible to easily mold even shapes that could not be realized in the past. Based on these points, we investigated the flow of the rhomboid tube group that could not be created before and the effect of self-excited vibration on the temperature field.

Cold spray (CS) is a thermal spraying method in which solid particles are mixed with an inert gas, accelerated at supersonic speed through a Laval nozzle, and collide with a substrate to form coating. The particle adhesion rate in CS nozzle strongly depends on the gas velocity of the working gas. Therefore, it is important to understand the flow condition inside the CS nozzle which accelerated the gas flow. One of the most traditional methods to diagnose the internal flow is to measure static pressure through thin ports. Although this method can accurately estimate the internal flow, it is not practical to apply to the commercial CS nozzle. Therefore, there is a need for a non-destructive measurement technique that can easily monitor the internal flow of the nozzle. In this study, we focused on the fact that the temperature of the compressible fluid depends on the velocity, and investigated the Mach number estimation method using the outer surface temperature of the nozzle. In addition, the Mach number obtained from the estimation method and the static wall pressure in the nozzle was compared to clarify the validity of the method.

According to the downsizing of automotive equipment, the present report discussed the heat exchange efficiency in intercoolers used in turbochargers system, etc. Due to the downsizing, low-flow-rate heat exchanger such as installed in a sub-radiator, or the electronic devices in hybrid and electric vehicles. In a low flow rate regime, we can propose a method for promoting convective heat transfer by installing a protrusion on the surface to generate a calm swirling flow. In this study, we visualized the flow using a temperature-sensitive liquid crystal that promotes the heat transfer coefficient while suppressing the increase in pressure loss caused by the method of generating swirl flow with protrusions. In this study, experiments were conducted using a model of the tube part without cooling fins. The size of the channel is 16mm x 120mm x 1.2mm. We visualized the flow using the temperature-sensitive liquid crystal that promotes the heat transfer coefficient while suppressing the increase of pressure loss caused by the method of generating the swirl flow by the protrusion using the temperature-sensitive liquid crystal. From the results obtained in the temperature-sensitive liquid crystal experiment and the results obtained from the numerical analysis, it can be confirmed that the temperature distribution of the entire flow path is increased by installing V-shaped projections. Therefore, it can be said that it is necessary to improve the experimental apparatus in the future and compare the obtained temperature boundary layer with the approximate solution to confirm the validity of the experiment.

Abstruct In semiconductor production, efficiency and precision of the cleaning process are very important. In this study, we handle “single wafer cleaner” that is one of the washing methods in the way of blowing air to a wafer with a turning disk at a high speed. However, the flow in the device becomes turbulence, which causes a problem that water drops and dusts reattach to the wafer surface. It is necessary to understand the flow in the device exactly to solve this problem. In the previous study, we found that there were “large-scale vortices” appearing inside the device, which causes particle reattaching to the wafer. In this study, we studied how they were created or disappeared. We found that the vortices were related to the speed of the rotating disk and the downflow rate.

The sorting devices of microfluidic system have a passive method and an active one. Curved microchannels are often used in these systems due to secondary flows. Because sorting or mixing can be used with the secondary flow in these systems, it is necessary to clarify the characteristic of the secondary flow. In this study, we investigate behavior of particles in spiral rectangular microchannel, and effects of aspect ratio and of Dean number De on the particle sorting. We performed three-dimensional numerical simulations using the particle tracking method (PTM) to analyze the particle sorting. When particle density is larger than water density, it is found that good sorting is obtained in the case of 20 < De < 40. This tendency appears to be stronger if the aspect ratio is small.

We studied on the drag reduction of CNF (cellulose nano fiber), that is a natural polymer, on the friction in a pipe flow. The fibers of CNF are characterized by the fact that into density in about one-fifth of iron while the strength is five times that of iron. Therefore, it attracts a lot of attention in material industries.

It is known that adding polymers to water in the pipe flow significantly reduces the coefficient of pipe friction as compared with water all. If you can understand the drag reduction of pipe friction resistance, one is understood can save energy. In this study, the pressure difference and the flow velocity of the water with CNF were measured, and the relationship between them was investigated to confirm the effect of CNF on reducing the pipe friction resistance.

In this study, the velocity profile acquisition technique based on laser Doppler velocimetry, which have a variable-focal system was proposed. As the variable-focal system, the focus tunable lens was installed in the transmitting optics. The proposed technique provided us that it became possible to obtain the velocity profile for axial direction without any mechanical scanning systems. The velocity profile in a parallel plate channel was measured to demonstrate the proposed technique. The calibration procedure of the technique and its validity were also described.

For energy management in industrial plants, it is important to monitor actual consumption of steam in each usage place. In order to measure the steam flow rate in existing pipes, clamp-on ultrasonic flowmeter is one of the effective solution. However, it is difficult to accurately measure the steam flow rates because of the large acoustic impedance difference between the pipe material and fluid, signal attenuation in the fluid, and high temperature. Hence, in this study, a new signal processing method using standard deviation of the target signal of the transmitted ultrasonic is proposed. Ultrasonic transmission experiments were carried out in air-water two-phase and saturated steam flows. Two ultrasonic sensors located at up- and down-stream positions were used for the measuring ultrasonic time-of-flight that depends on the flow rate. In air-water two-phase flows, it was shown that flow rate measurements were difficult with increasing of the flow velocity and the wetness fraction. However, the transit time difference of the ultrasonic signals transmitted from the upstream and downstream transducers could be accurately obtained using the proposed method. Furthermore, distributions of the standard deviation were influenced with the flow conditions. Uniqueness shape of the target signal in the standard deviation were also confirmed in the steam flow conditions. Thus, it implies that the proposed method is useful for measuring steam flows.

In an emulsion emulsified and mixed with water and fuel oil, the fuel that causes the micro-explosion when the superheat limit of water is exceeded during combustion is called emulsified fuel. One of the biggest problems for putting it into practical use is emulsion instability. It is important to prevent the malfunction of an internal combustion engine and get the effect of exhaust gas reduction. The stability of emulsion fuel is obtained by preventing a creaming in which the water droplets of dispersed phase settle and stratify due to the density difference from the fuel oil of the continuous phase. The settling shear velocity is decided by the droplet size. In this study, we focused on the measurement using the ultrasonic waves that reflected an attenuated at the interface of the medium with different acoustic impedance. In this report, we produced 10 %, 20 %, 30 % water-vegetable oil emulsified fuel with a Taylor-Couette reactor and measured it utilizing ultrasonic echo attenuation and compared it with ultrasonic velocity profiler. As a result, the ultrasonic attenuation coefficient tended to increase as the inner cylinder rotation speed increased. Furthermore, vibrations of the flow velocity profiles occurred at 500 rpm and 600 rpm at 10 and 20% W/O emulsion, whereas such vibration was not seen at 30% W/O emulsion.