Faculty Profiles - UCHIYAMA, Tomomi

Papers - UCHIYAMA, Tomomi

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Numerical simulation of the flow and performance of a Savonius hydraulic turbine provided with a shield plate

TAKAMURE Kotaro, GU Qiang, DEGAWA Tomohiro, UCHIYAMA Tomomi, IIO Shouichiro, IKEDA Toshihiko

Transactions of the JSME (in Japanese) Vol. 86 ( 887 ) page： 20-00181 - 20-00181 2020

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

The flow and performance of a rotor of a Savonius hydraulic turbine provided with a shield plate were analyzed by the two-dimensional simulations. The rotor diameter DR is 142 mm, and the Reynolds number based on the velocity of the main flow U0, U0DR/ν, is 1.1×105. The shield plate with a length of 0.5DR is installed upstream of the rotor, perpendicular to the main flow. The comparative experimental studies have visualized the flow and clarified that the shield plate increases the power output of the rotor. The vortex in cell method combined with the volume penalization method was applied to the flow simulation, and the torque acting on the rotor was computed with a custom method by the authors. The simulated flows around the shield plate and rotor agreed with the experimentally visualized ones. The simulation successfully revealed the effect of the shield plate on the flow and power output of the rotor. These demonstrate the applicability of the present simulation method for the performance prediction of the rotor of Savonius hydraulic turbines provided with a shield plate.

DOI： 10.1299/transjsme.20-00181

CiNii Research

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

TAKAMURE Kotaro, Uchiyama Tomomi

The Proceedings of the Fluids engineering conference Vol. 2020 ( 0 ) page： OS03-10 - 10 2020

Effect of uniaxial through hole on the falling behavior of hollow and solid spheres in water

TANAKA Junki, KATO Kaede, TAKAMURE Kotaro, UCHIYAMA Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2020 ( 0 ) page： S05129 2020

Energy transition of a sphere launched upward from stationary water toward air

TAKAMURE Kotaro, Uchiyama Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2020 ( 0 ) page： S05110 2020

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

In a present experiment, a solid sphere with a density of 2600 kg/m3 and diameter of 25.4 mm was launched vertically upward in water toward the air-water interface. The submergence depth was changed and the launch velocity was adjusted so that the Reynolds number of the sphere immediately after passing the air-water interface was almost equal at each submergence depth. The energy ratio Ep/Ek was defined as the ratio of the kinetic energy Ek of the sphere immediately after it passed through the air-water interface to the potential energy Ep when the sphere reached the maximum displacement position. Ep/Ek decreased when the submergence depth was H/d < 3. However, it had a constant value of Ep/Ek ~ 0.57 when the submergence depth was H/d ≥ 3. In addition, when the submergence depth was H/d ≥ 3, the ratio of each energy became similar immediately after passing through the water surface. This indicated that each energy distribution had reached the equilibrium state.

DOI： 10.1299/jsmemecj.2020.s05110

CiNii Research

Effect of uniaxial through hole on the falling behavior of a hollow sphere in water

The Proceedings of Conference of Tokai Branch Vol. 2020.69 ( 0 ) page： 602 2020

Experimental study of mixing of two-layer density-stratified fluid by a vortex ring

Cao L., Ito R., Degawa T., Matsuda Y., Takamure K., Uchiyama T.

ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019 Vol. 5 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019

This study experimentally investigates the mixing of a two-layer density-stratified fluid of water (upper layer) and aqueous sodium chloride (NaCl) solution (lower layer) induced by the interaction between a vortex ring and the density interface. The vortex ring, which consists of water, is launched from an orifice in the upper layer toward the density interface, after which its motion, along with the behavior of the lower fluid, is visualized through a planar laser-induced fluorescence method. The Atwood number that expresses the nondimensional density jump across the density interface is set at 0.0055, and the Reynolds number Re of the vortex ring is varied from 2050 to 3070. The visualization experiment clarifies that the vortex ring penetrating the density interface is bounced while collapsing in the lower fluid. Furthermore, it elucidates that the bounced upper fluid entrains the lower fluid into the upper layer by inducing a second vortex ring consisting of the lower fluid. Thus, this study reveals the effect of Re on the mixing of the upper and lower fluid induced by the launched vortex ring.

DOI： 10.1115/AJKFluids2019-4972

Scopus

Flow and Noise Characteristics of Cavitating Jet Issuing from a Rectangular Orifice for Various Aspect Ratios

TAKEI Hironori, WATANABE Akari, IIO Shouichiro, YOSHIDA Futoshi, UCHIYAMA Tomomi

The Proceedings of the Fluids engineering conference Vol. 2019 ( 0 ) page： OS3-23 - 23 2019

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

Cavitation is one of the significant issues for water hydraulic components. This study focuses on the relationships between the cavitation phenomenon and noise under various pressure condition. Cavitating jet from a rectangular orifice with different aspect ratio was investigated in this study to reveal the critical parameter for the cavitation in a water hydraulic spool valve. The author performed flow visualization and noise measurement. The experimental results showed that the relationship between jet behavior and noise characteristics. The noises of all aspect ratio jets had a peak at the same positive downstream pressure. The both of cavitation and noise were suppressed for the largest aspect ratio of AR=52.0.

DOI： 10.1299/jsmefed.2019.os3-23

CiNii Research

Motion of a Solid Sphere Launched Vertically Upward toward Water Surface and the Behavior of Air-Water Interface Induced by the Sphere

TAKAMURE Kotaro, UCHIYAMA Tomomi

The Proceedings of the Fluids engineering conference Vol. 2019 ( 0 ) page： OS3-08 - 8 2019

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

To investigate the variation in a sphere's motion and the behavior of the air-water interface induced by the sphere, a solid sphere is launched vertically upward in water toward the air-water interface. Four spheres with different densities ρp were studied: a stainless steel sphere (ρp = 7930 kg/m3), an alumina sphere (ρp = 3900 kg/m3), a Teflon sphere (ρp = 2180 kg/m3), and a Duracon sphere (ρp = 1360 kg/m3). By experimentally visualizing the sphere motion in water, their launch velocity can be set with high accuracy. When a sphere passes through the air--water interface, it makes the interface more complex and entrains water. Additionally, spheres with a small value of ρp were demonstrated to not always vertically collide with the air--water interface.

DOI： 10.1299/jsmefed.2019.os3-08

CiNii Research

Flow around Bluff Body within Bubble Plume

UCHIYAMA Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2019 ( 0 ) page： W05102 2019

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

This article describes the flow around bluff body in microbubble plume. Firstly, the flow around two circular cylinders arranged in tandem within a microbubble plume was investigated. The experiment revealed the water and bubble shear layers originating at the sides of the lower cylinder, and allowed the elucidation of their behavior around the upper cylinder. Secondly, the motion of a solid spherical particle in a microbubble plume and the behavior of bubbles around the particle were studied. The studies clarified the bubble distribution and velocity around the particle.

DOI： 10.1299/jsmemecj.2019.w05102

CiNii Research

Flow around Two Circular Cylinders Placed Tandemly Inside a Microbubble Plume

UCHIYAMA Tomomi, KANO Ryota, DEGAWA Tomohiro, TAKAMURE Kotaro

The Proceedings of the Fluids engineering conference Vol. 2019 ( 0 ) page： OS3-07 - 7 2019

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

This study investigates the flow past two cylinders arranged in tandem within a microbubble plume inside a tank. Microbubbles with a mean diameter of 0.055 mm are released by water electrolysis from electrodes placed at the bottom of the tank. Upon rising, these microbubbles induce an upward water flow around them due to buoyancy. Orthogonally to the axis of this microbubble 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. The bubbles and the water flow around the cylinders are visualized, and the bubble velocity distribution is measured. The experiments reveal the water and bubble shear layers originating at the sides of the lower cylinder, and allow the elucidation of their behavior around the upper cylinder. Furthermore, this study makes clear the effects of L on the flow around the two cylinders, such as the stagnant bubbly flow and the bubbly wake.

DOI： 10.1299/jsmefed.2019.os3-07

CiNii Research

Numerical Simulations of the Flow and Performance of a Hydraulic Savonius Turbine by the Vortex in Cell Method with Volume Penalization

TAKAMURE Kotaro, UCHIYAMA Tomomi, GU Qiang, DEGAWA Tomohiro, Iio Shouichiro, IKEDA Toshihiko

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2019 ( 0 ) page： S05121 2019

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

This study is concerned with the numerical simulations of the flow and performance of a rotor of a hydraulic Savonius turbine. The flow was simulated using the vortex in cell (VIC) method in combination with the volume penalization (VP) method. The torque acting on the rotor was computed using a custom method, which can accurately calculate the fluid forces on solid bodies in flows simulated by the VIC-VP method, to analyze the rotational speed and power output of the rotor. The simulated flow around the rotating blades agreed qualitatively with the experimentally visualized flow, and the analyzed relation between the rotor's rotational speed and power output agreed well with the experimentally measured relation. These demonstrate that the VIC-VP method in combined with the authors' method for calculating fluid forces is applicable for the simulations of flow and performance of hydraulic Savonius turbines.

DOI： 10.1299/jsmemecj.2019.s05121

CiNii Research

Numerical Simulation of Pin-on-disk Sliding Lubricated with Nanometer-thick Liquid Film by MPS Method

WATABE Shotaro, Uchiyama Tomomi, TAKAMURE Kotaro, ZHANG Hedong, DEGAWA Tomohiro

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2019 ( 0 ) page： S16105P 2019

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

Pin-on-disk sliding tests have been carried out to investigate lubrication properties of nanometer-thick liquid films. However, it is difficult to experimentally observe the detailed flow behavior of the films at the nanoscale contacting interface. To solve this problem, we performed numerical simulations with the moving particle semi-implicit (MPS) method in this study. To model a pin sitting on a rotating disk lubricated with a nanometer-thick liquid film, the effects of surface tension and external force were taken into account in the governing equation. As a result, details of the behavior of the film and pin and their interference were visualized. This result suggests that the MPS method is potentially useful for clarifying the mechanism of lubrication with nanometer-thick liquid films.

DOI： 10.1299/jsmemecj.2019.s16105p

CiNii Research

Flow past two cylinders arranged in tandem within a microbubble plume

Uchiyama T., Kano R., Degawa T., Takamure K.

ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019 Vol. 5 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019

This study investigates the flow past two cylinders arranged in tandem within a microbubble plume inside a tank. Microbubbles with a mean diameter of 0.055 mm are released by water electrolysis from electrodes placed at the bottom of the tank. Upon rising, these microbubbles induce an upward water flow around them due to buoyancy. Orthogonally to the axis of this microbubble 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. The bubbles and the water flow around the cylinders are visualized, and the bubble velocity distribution is measured. The experiments reveal the water and bubble shear layers originating at the sides of the lower cylinder, and allow the elucidation of their behavior around the upper cylinder. Furthermore, this study makes clear the effects of L on the flow around the two cylinders, such as the stagnant bubbly flow and the bubbly wake.

DOI： 10.1115/AJKFluids2019-4971

Scopus

Flow around Bluff Body within Bubble Plume

UCHIYAMA Tomomi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2019 ( 0 ) page： W15102 2019

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

DOI： 10.1299/jsmemecj.2019.w15102

CiNii Research

Development of a propeller-type hollow micro-hydraulic turbine with excellent performance in passing foreign matter

Uchiyama Tomomi, Honda Satoshi, Degawa Tomohiro

RENEWABLE ENERGY Vol. 126 page： 545 - 551 2018.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd

This study develops a micro-hydraulic turbine with excellent performance in the passage of foreign matter included in the water flow. The runner has four blades, with a circular hollow around the rotating axis to pass foreign matter through the runner. The ratio of the hollow diameter D2 to the runner outer diameter D1, D2/D1, is defined as the hollow ratio ε. Laboratory experiments are conducted by introducing polyester fibers into the water flow as foreign matter. The turbine efficiency η decreases with increasing ε under the fiber-free condition. For the runner having no hollow (ε = 0), η decreases drastically with increasing the mass of the introduced fibers. This is due to the blockage of the runner by the fibers. But η for the runners provided with the hollow decreases less. This demonstrates that the hollow makes the fibers pass successfully through the runner. Additional experiments are conducted using the runner with ε = 0.25. The blade leading edges near the central axis are rounded with radius R. When R/D1 = 0.1875, the decrease in η due to the fibers is extremely small. The rounded leading edges successfully prevent the runner from catching the fibers, demonstrating that they effectively heighten the passage performance of foreign matter through the runner.

DOI： 10.1016/j.renene.2018.03.083

Web of Science

Scopus

Improvements to the convection scheme in the vortex particle method using a semi-Lagrangian method

Degawa Tomohiro, Uchiyama Tomomi

JOURNAL OF ALGORITHMS & COMPUTATIONAL TECHNOLOGY Vol. 12 ( 3 ) page： 223-233 - 233 2018.9

Mixing of density-stratified fluid in a cylindrical tank by a diagonal jet Reviewed

Tomohiro Degawa, Kota Uno, Tomomi Uchiyama

Journal of Energy and Power Engineering Vol. 12 page： 436-443 2018

Mixing of density-stratified fluid in a cylindrical tank by a diagonal jet Reviewed

Tomohiro Degawa, Kota Uno, Tomomi Uchiyama

Journal of Energy and Power Engineering Vol. 12 page： 436-443 2018

Falling of a Spherical Particle in Microbubble Plume and Microbubble Behavior around the Particle

UCHIYAMA Tomomi, KAWASAKI Yujiro, DEGAWA Tomohiro

The Proceedings of the Fluids engineering conference Vol. 2018 ( 0 ) page： OS5-20 - 20 2018

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

This study conducts experimental exploration on the motion of a solid spherical particle falling in a microbubble plume and the bubble behavior around the particle. Bubbles with a mean diameter of 0.037 mm, released into a rectangular conduit using the electrolysis of water, rise by the buoyant force and induce a bubble plume. A spherical particle with a diameter 11.1 mm and density 1130 kg/m3 is released from the top of the conduit. The experiment clarifies that the particle falls meandering through the plume and that the terminal velocity is almost the same as that for a particle falling in quiescent water. The experiment also makes clear that the bubbles separate from the particle surface and that the separation induces a stagnation area just behind the particle. A wake still exists at a location with a distance of three times of the particle diameter from the particle.

DOI： 10.1299/jsmefed.2018.os5-20

CiNii Research

Motion of a Spherical Particle in Microbubble Plume and Bubble Behavior around the Particle

UCHIYAMA Tomomi, DEGAWA Tomohiro, KAWASAKI Yujiro

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2018 ( 0 ) page： S0510401 2018

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

This study investigates the motion of a spherical particle in microbubble plume and the bubble behavior around the particle. Microbubbles with a mean diameter of 0.037 mm, released into a rectangular conduit using the electrolysis of water, rise by the buoyant force and induce a bubble plume in the conduit. A spherical particle with a diameter 10 mm and a density 1022 kg/m3 is placed on a mesh stretched near the bottom of the conduit at the commencement of the microbubble release from the cathode. The experiments clarify the effects of the bubble volumetric flux on the motion of the particle. They also explore the bubble distribution and velocity around the rising, still and lowering particle to make clear the front stagnation and wake of the particle.

DOI： 10.1299/jsmemecj.2018.s0510401

CiNii Research

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Papers - UCHIYAMA, Tomomi