Faculty Profiles - UCHIYAMA, Tomomi

Development of Desktop Air Curtain System to Block Aerosols in Exhaled Breath

TAKAMURE Kotaro, SAKAMOTO Yasuaki, YAGI Tetsuya, IWATANI Yasumasa, AMANO Hiroshi, UCHIYAMA Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2022 ( 0 ) page： S055-10 2022

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

A desktop-type air curtain device capable of being installed on a desk to protect healthcare workers from infectious diseases was developed. Pseudo-exhaled air containing aerosol particles emitted from a mannequin was blown toward the air curtain generated by the air curtain device. The aerosol blocking effect of the air curtain device was investigated using particle image velocimetry measurements. Air curtain flow was maintained inside the gate of the air curtain device. The aerosol particles approaching the air curtain device were observed to abruptly bend towards the suction port without passing through the gate, signifying that the aerosol particles were blocked by the air curtain flow.

DOI： 10.1299/jsmemecj.2022.s055-10

Falling behavior of hollow particle with uniaxial through-hole: A case study using experiments and numerical simulations

Takamure, K; Tanaka, J; Kato, H; Uchiyama, T

POWDER TECHNOLOGY Vol. 392 page： 367 - 374 2021.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Powder Technology

In this study, experiments and numerical simulations are performed where a hollow particle with a uniaxial through–hole is dropped freely in water, and its behavior is investigated. The distribution of falling particle trajectories reveals significant deviation in the direction perpendicular to the through–hole of the particle. In addition, the pressure distribution at the particle surface and the vorticity field of the wake of the particle are distributed asymmetrically in the plane perpendicular to the through–hole of the particle. Conversely, this pressure distribution and vorticity field are distributed symmetrically with respect to the direction parallel to the through–hole of the particle. Thus, this study clarifies that the movement of the particle in the direction parallel to the through–hole is suppressed. These results provide valuable novel insights into the control of particle motion.

DOI： 10.1016/j.powtec.2021.07.020

Effect of Froude number on the motion of a spherical particle launched vertically upward in water

Takamure, K; Uchiyama, T

EXPERIMENTAL THERMAL AND FLUID SCIENCE Vol. 128 2021.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Experimental Thermal and Fluid Science

A spherical particle with a diameter of 25.4 mm and density of 2640 kg/m3 was launched vertically upward toward the free surface of calm water. The Froude number of the particle passing through the water surface was varied. The dependence of the Froude number on the particle motion and water surface behavior was investigated from the instant the particle crossed the water surface until it attained its maximum displacement position. Based on the classical energy conservation law, the energy lost in the interaction between the particle and water surface (i.e., interface containing energy, Eo) was estimated. Eo was found to increase with the increase in the Froude number when the particle crossed the water surface. In addition, owing to Eo at the maximum displacement position of the spherical particle, the height and width of the interfacial water sheet changed by the same ratio at the point of intersection of the upper side of the particle with the calm water surface. This result was in agreement with that obtained by changing the submergence depth, as reported by Takamure and Uchiyama (2020). This finding suggests that the characteristics of the interfacial water sheet are the dominant parameters influencing the interface containing energy. The presented findings can help determine the parameters to model the water exit problem.

DOI： 10.1016/j.expthermflusci.2021.110453

Behavior of a solid sphere launched vertically upwards in water and its interaction with the air-water interface

Takamure K., Uchiyama T.

OCEAN ENGINEERING Vol. 235 2021.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ocean Engineering

An experiment was conducted in which a solid sphere with a density of 1,875 kg/m3 and diameter of 24.8 mm was launched vertically upwards in water towards the air–water interface. By changing the Reynolds number, Re, based on the launch velocity, the motion of the sphere due to interference with the air–water interface was investigated along with the behavior of the interface. The experimental results of the sphere's vertical position in water agree with the theoretical values. However, in air, the experimental results gave lower vertical positions than the theoretical values. When the Reynolds number where the sphere reaches the air–water interface is Rew1¯=0.2×103, the vertical trajectory of the sphere branches above and below the ensemble average immediately after passing the air–water interface. This difference in bifurcation does not depend on the Reynolds number in water. However, no branching occurs when Rew1¯ is large. There is an inverse relationship between the asymmetry of the air–water interface that occurs when the sphere passes through the interface and the sphere's maximum displacement. It was shown that the energy loss of the sphere and the asymmetry of the air–water interface have a linear relationship in all cases with different Reynolds numbers. This means that there is a invariant relationship between the energy lost by the sphere passing through the air–water interface and the asymmetry of the interface.

DOI： 10.1016/j.oceaneng.2021.109282

Falling of a Spherical Particle in Fine-Bubble Plume and Fine-Bubble Behavior around the Particle

Takamure K., Kawasaki Y., Degawa T., Uchiyama T.

FLUID DYNAMICS Vol. 56 ( 5 ) page： 612 - 621 2021.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Fluid Dynamics

Abstract—: In this study, the interaction between a spherical solid particle descending in a fine-bubble plume and the fine-bubbles around the particle is investigated experimentally. The fine-bubbles, which are formed by water electrolysis and have an average diameter of 0.037 mm, rise via buoyancy to form bubble plumes. The average bubble velocity in the conduit is 0.05 mm/s. A spherical solid particle with a diameter of 11.1 mm and a density of 1130 kg/m3 is dropped into the fully-developed bubble plume. The particle falls in a meandering motion in the fine-bubble plume. In this process, the terminal velocity of the particles falling in the fine-bubble plume is almost identical to that of a particle falling in the quiescent water. Additionally, after the fine-bubbles have been separated from the particle surface, they flow into the wake of the particle, forming a stagnant region. The particle wake diameter increases threefold, as compared with its value in the downstream direction of the fine-bubble plume.

DOI： 10.1134/S001546282105013X

Mixing of a two-layer density-stratified fluid by two vortex rings successively launched toward the density interface

Cao, LL; Takamure, K; Degawa, T; Uchiyama, T

JOURNAL OF VISUALIZATION Vol. 24 ( 4 ) page： 683 - 697 2021.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Visualization

Abstract: In this study, two vortex rings composed of upper fluid were continuously ejected vertically downward toward the interface of the two-layer density-stratified fluid. The motion of the vortex rings and behavior of the lower layer fluid were investigated via visualization experiment, and the effect of time interval between the injections of the two vortex rings on the mixing of the density-stratified fluid was investigated. The first emitted vortex ring (VRA) advected vertically downward in the upper layer, passed through the density interface, and then advected in the lower layer. After VRA reached the maximum depth in the lower layer, the upper part of the fluid mass ejected into the upper layer due to buoyancy. The lower fluid was entrained in the upper layer. Subsequently, a new vortex ring (VRC) was generated by the fluid mass ejected in the upper layer and advected vertically upward in the upper layer. The second vortex ring emitted (VRB) collided with the tip of the fluid mass of the VRA ejected from the lower layer. Subsequently, it slightly penetrated the lower layer, rolled up the lower layer fluid into the upper layer, and coalesced with VRC to collapse. In the process of vortex merging, the mixing of the upper and lower layers reached a maximum when the VRA reached the maximum depth. Furthermore, it was clarified that the mixing ability of the upper and lower layers depends on the ejection time interval of the two vortex rings. Graphic abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s12650-020-00738-8

Vortex-in-cell simulation of the flow and performance of a Savonius hydraulic turbine with S-shaped blades

Takamure, K; Wang, HT; Uchiyama, T; Iio, S; Ikeda, T

JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY Vol. 13 ( 4 ) 2021.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Renewable and Sustainable Energy

The volume penalization vortex-in-cell (VP-VIC) method, which combines the vortex-in-cell and vortex penalization methods, is a kind of immersed boundary method that has the advantage of accurately calculating the vorticity field near the boundary. It is expected to be used as a design tool for shape optimization. In this study, the flow and performance of a small Savonius turbine rotor (rotor diameter DR = 245 mm) with S-shaped blades, which is used for small-scale distributed power generation with output less than 100 kW, were analyzed by numerical simulation. The results were compared with those of previous experimental studies to examine the usefulness of the VP-VIC method for fluid analysis around the Savonius turbine. The Reynolds number (Re=U0DR/ν) based on the streamwise velocity U0 is 1.32×105. The volume penalization vortex-in-cell (VP-VIC) method is applied for flow simulation, and the rotational motion of the rotor is analyzed using the calculation method previously proposed by the authors for the fluid force acting on the solid boundary (blade surface). As a result, the relationship between the rotational speed of the rotor and the output coefficient obtained in this simulation is similar in the experimental results of Golecha et al. [Appl. Energy 88, 3027-3217 (2011)] using S-shaped blades. In particular, with an increase in the load torque, the rotational speed of the rotor decreases, and the rotor stops momentarily. When the rotor stops, the positive torque of clockwise rotation acts on the advancing blade, while the negative torque of counterclockwise rotation acting on the returning blade decreases; hence, the rotor restarts immediately after stopping. In addition, it is established that the rotor output can be accurately predicted. Based on the above, it is reconfirmed that the VP-VIC method is beneficial for predicting the performance of a Savonius turbine.

DOI： 10.1063/5.0051203

Development of a self-powered wireless sensor node to measure the water flowrate by using a turbine flowmeter

Uchiyama, T; Takamure, K; Okuno, Y; Sato, E

INTERNET OF THINGS Vol. 13 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Internet of Things (Netherlands)

A self-powered wireless sensor node was developed to measure the water flowrate. It is composed of a turbine flowmeter and an IoT control unit. The turbine flowmeter generates electric power from the rotation of the rotor. The IoT control unit, consisting of a microcomputer and a low power wide area (LPWA) communication module, uses the power generated by the rotor rotation to detect the rotational speed of the rotor (the water flowrate) and to communicate wirelessly with a server on the Internet. Experiments were also conducted to evaluate the performance of the sensor node. The power generated by the rotor rotation was sufficient to operate the wireless sensor node as a self-powered unit. The full-scale accuracy and indication accuracy of the measured flowrate were 1.2% and 2.8%, respectively. The wireless sensor node could stably upload the measured flowrate to a server on the Internet.

DOI： 10.1016/j.iot.2020.100327

Motion of a Solid Sphere Launched Vertically Upward in Water and Deformation of Water Surface by the Sphere

Takamure K., Uchiyama T.

Lecture Notes in Mechanical Engineering page： 159 - 166 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Lecture Notes in Mechanical Engineering

A solid sphere is launched vertically upward from water toward the air–water interface, and the modulation of the sphere’s motion and the behavior of the air–water interface induced by the sphere are investigated. Spheres with three different densities ρp are used: the almina sphere (ρp = 3900 kg/m3), teflon sphere (ρp = 2180 kg/m3), and duracon sphere (ρp = 1360 kg/m3). Through a visualization experiment on the motion of a sphere in water, it was demonstrated that the launch velocity of the sphere can be set with high accuracy. When the sphere passes through the air–water interface, it forms a complex interface while entraining water. Additionally, spheres with small ρp were demonstrated to not always vertically collide with the air–water interface; this causes different behaviors of the spheres in the air.

DOI： 10.1007/978-981-15-5183-3_17

Flow Characteristics of Cavitating Jet through a Rectangular Orifice with Different Aspect Ratios

TERAKWA Kohei, IIO Shouichiro, TAKAMURE Kotaro, UCHIYAMA Tomomi

The Proceedings of Conference of Hokuriku-Shinetsu Branch Vol. 2021.58 ( 0 ) page： F021 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

A spool valve for water hydraulics, Aqua Drive System (ADS), which uses tap water, has some rectangular openings at control ports for precise control because of the low viscosity of the water. In the valve, cavitation happens quickly, and it occurs some troubles, e. g. noise and vibration, erosion, degradation of controllability. This study focuses on cavitation behavior and cavitation-related noise and pressure-flow rate characteristics of a rectangular orifice. Jet flow behavior issuing from a rectangular orifice strongly depends on its aspect ratio. So, cavitation could be affected by the aspect ratio. However, there is little knowledge of the relationships between the aspect ratio and cavitation noise or pressure-flow rate. This research investigates the aspect ratio influence on cavitation, noise, and pressure-flow rate characteristics with different pressure conditions. The equivalent diameter of the orifice used in this study is from 0.35 to 1.3mm, and it is based on a product spool valve model. As a result, the cavitation jet behavior changes with the orifice aspect ratio and the ambient pressure. But the noise characteristics show the almost same tendency for different aspect ratio.

DOI： 10.1299/jsmehs.2021.58.f021

Visualization and Flow Characteristics of a Cavitating Jet from a Rectangular Orifice with Various Aspect Ratios

TAKEI Hironori, TERAKAWA Kohei, IIO Shouichiro, TAKAMURE Kotaro, UCHIYAMA Tomomi, YOSHIDA Futoshi

The Proceedings of the Fluids engineering conference Vol. 2021 ( 0 ) page： OS03-20 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

This study focused on the characteristics of a cavitating jet issuing from a small rectangular orifice with different aspect ratios. The orifice size is similar to the control port in a water hydraulic spool valve. The authors conducted the flow visualization to capture the overall and cross-sectional jet images. The maximum Reynolds number based on the equivalent diameter is approximately 1.3×105. The results show that cavitation bubbles generate in the jet shear layer and just downstream the jet exit. The shape of the cavitation region varies with the streamwise position except for the two-dimensional orifice having an aspect ratio (AR) of 38.3. In the square orifice, the cavitation region rotates at 45 degrees from the jet exit like an axis switching. The cavitation region in the jet of AR=6.76 deforms from the rectangular shape. On the other hand, under the large aspect ratio condition, the shape of the cavitation region is maintained relatively downstream.

DOI： 10.1299/jsmefed.2021.os03-20

Effect of initial angle of through-hole of sphere on the motion of a sphere launched vertically in water

TAKAMURE Kotaro, UCHIYAMA Tomomi

The Proceedings of the Fluids engineering conference Vol. 2021 ( 0 ) page： OS03-04 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

A sphere with a uniaxial through-hole of 6mm with a sphere diameter of 25.4 mm and density of 1360 kg/m3 was launched vertically upward toward the free surface of calm water. The effect of initial angle of the uniaxial through-hole was investigated from the time the sphere passed through the calm water surface until it attained its maximum displacement position. When uniaxial through-hole of the sphere and the water surface are horizontal, a slight rotation occurs in the sphere that rises in the water. As the initial angle of the uniaxial through-hole increases, the sphere over the water surface deviates greatly from the central axis.

DOI： 10.1299/jsmefed.2021.os03-04

Characteristics of the wake of a sphere with a uniaxial through hole in uniform flow

KATO Hayato, TAKAMURE Kotaro, UCHIYAMA Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2021 ( 0 ) page： S051-09 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

In this study, we investigated the characteristics of the wake of a sphere with a uniaxial through-hole．The sphere diameter was 25.4 mm, and the through-hole diameter was 6 mm. The sphere was placed in a uniform flow so that the through-hole is perpendicular to the streamwise direction. The Reynolds number based on the sphere diameter and the uniform flow velocity was 12,000. The flow velocity was measured by a hot-wire anemometer. As a result, the velocity defect of the sphere was smaller than that of a sphere without such through-hole. However, the significant differences were hardly observed as the flow moves toward the downstream direction.

DOI： 10.1299/jsmemecj.2021.s051-09

Development of a self-powered wireless sensor node measuring water flowrate using a turbine flowmeter

SAKAMOTO Yasuaki, UCHIYAMA Tomomi, TAKAMURE Kotaro, OKUNO Yuta, SATO Eiichi, NAKAYAMA Hiroshi, OSA Noburo, MATSUMOTO Hiroyuki

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2021 ( 0 ) page： S144-01 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

A self-powered wireless sensor node was developed to measure the water flowrate. It is composed of a turbine flowmeter and an IoT control unit. The IoT control unit, consisting of a microcomputer and a low power wide area communication module, uses the power generated by the rotor rotation to detect the rotational speed of the rotor (the water flowrate) and to communicate wirelessly with a server on the Internet. Experiments were also conducted to evaluate the performance of the sensor node. The power generated by the rotor rotation was sufficient to operate the wireless sensor node as a self-powered unit. The full-scale accuracy and indication accuracy of the measured flowrate were 1.2 % and 2.8 %, respectively. The wireless sensor node could stably upload the measured flowrate to a server on the Internet.

DOI： 10.1299/jsmemecj.2021.s144-01

Improvement of Power Generation Efficiency of Self-powered Turbine Flowmeter with NACA airfoil Shaped Blades

SAKAMOTO Yasuaki, UCHIYAMA Tomomi, TAKAMURE Kotaro, NAKAYAMA Hiroshi

The Proceedings of the Fluids engineering conference Vol. 2021 ( 0 ) page： OS03-15 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

The purpose of this study is to improve the power generation efficiency of the self-powered turbine flowmeter developed by the authors. To increase the efficiency, the NACA airfoil was applied to the blade of the rotor. It was shown that the efficiency is favorably improved over the entire range of the flowrate by using the NACA airfoil blade.

DOI： 10.1299/jsmefed.2021.os03-15

Effect of density of a sphere launched vertically in water on the water-surface behavior and sphere motion in air

Takamure, K; Uchiyama, T

PHYSICS OF FLUIDS Vol. 32 ( 11 ) 2020.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Physics of Fluids

Submerged solid spheres with specific gravities relative to water ranging from 1.36 to 7.93 were launched vertically upward toward the free surface of calm water. The motion of each sphere and the behavior of the water surface were investigated from the time the sphere passed through the calm water surface until it attained its maximum displacement position. The energy lost in the interaction between the sphere and the water surface (i.e., the interfacial containing energy Eo) was estimated from energy conservation. A larger Eo at the maximum displacement position of the sphere led to a larger increase in the height and width of the interfacial water sheet where the upper side of the sphere intersected with the free surface of calm water. This result corresponded to the result obtained by changing the submergence depth, as reported by Takamure and Uchiyama ["Air-water interface dynamics and energy transition in air of a sphere passed vertically upward through the interface,"Exp. Therm. Fluid Sci. 118, 110167 (2020)]. This aspect suggests that the characteristics of the interfacial water sheet are the dominant parameters influencing Eo. The presented findings can facilitate the determination of parameters to model the water exit problem.

DOI： 10.1063/5.0024032

Dynamics of a sphere launched vertically in water

Takamure, K; Uchiyama, T

POWDER TECHNOLOGY Vol. 372 page： 246 - 257 2020.7

Effect of cylinders on the characteristics of a fine-bubble plume

TAKAMURE Kotaro, DEGAWA Tomohiro, KANO Ryota, UCHIYAMA Tomomi

Journal of Fluid Science and Technology Vol. 15 ( 3 ) page： JFST0019 - JFST0019 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

The characteristics of a fine-bubble plume passing through two tandem cylinders are investigated. Fine-bubbles with a mean diameter of 0.055 mm are released by water electrolysis from electrodes placed at the bottom of a tank. They induce an upward water flow around them with rising due to buoyancy. Orthogonally to the axis of such fine–bubble plume, two cylinders with a diameter D of 30 mm are arranged in tandem. The distance between the cylinders, L, ranges between 1.5D and 3D. This study visualizes the bubbles and water flow around the cylinders. It also measures the bubble velocity distribution. The experiments reveal the water and bubble shear layers originating at the sides of the lower cylinder and make clear their behavior around the upper cylinder. This study elucidates the effects of L on the characteristics of the fine-bubble plume, such as the stagnant bubbly flow and the bubbly wake around the cylinders.

DOI： 10.1299/JFST.2020JFST0019