Faculty Profiles - UCHIYAMA, Tomomi

Papers - UCHIYAMA, Tomomi

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Study of the Interactions between Rising Air Bubbles and Vortex Core of Swirling Water Flow around Vertical Axis

UCHIYAMA Tomomi, ISHIGURO Yukihiro

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2016 ( 0 ) page： S0520304 2016

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

The interactions between rising air bubbles and the vortex core of swirling water flows in a cylindrical tank are experimentally investigated. A stirring disc mounted at the center of the tank bottom is rotated to produce swirling water flows around the central (vertical) axis of the tank, and small air bubbles are successively released from tubules mounted near the stirring disc. The bubbles rise helically in the swirling water flow because of the buoyancy force, and some bubbles are entrained into the vortex core. The precessional amplitude of the vortex core is enhanced by the bubbles when the bubble flow rate Qg is very low. But it decreases with increasing Qg when Qg is larger than a certain value. In the horizontal cross-sections near the stirring disc, the bubbles make the water flow field non- axisymmetric and reduce the water velocity.

DOI： 10.1299/jsmemecj.2016.s0520304

CiNii Research

Numerical Study of Wall Wettabilities by Immersed Boundary-Lattice Boltzmann Method

SETA Takeshi, Uchiyama Tomomi, TAKANO Noboru

The Proceedings of the Fluids engineering conference Vol. 2016 ( 0 ) page： 0711 2016

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

We improve the accuracy and the numerical stability of the immersed boundary-lattice Boltzmann method (IB-LBM) to calculate the motion of a droplet on hydrophobic surfaces in complex geometry. To exactly derive the Chan-Hilliard equation, we use the proper source term proposed by Liang and the two-relaxation-time (TRT) collision operator. The series of the numerical tests, including Zalesak’s disk rotation, a single vortex, and a deformation of a sphere demonstrate that the computational effectiveness of the TRT collision operator is superior to that of the multi relaxation time collision operator. Analytical and numerical solutions of the symmetric shear flows demonstrate that the implicit diffuse direct-forcing method without the computational cost of the sparse matrix solver reduces the velocity slip and boundary value deviation as effectively as the implicit correction method for any relaxation times. The present IB-LBM with the TRT collision operator appropriately calculates the contact angle of liquids on the arbitrary shaped surfaces.

DOI： 10.1299/jsmefed.2016.0711

CiNii Research

Numerical study on the flow and performance of an open cross-flow mini-hydraulic turbine

Uchiyama Tomomi, Uehara Shou, Fukuhara Haruki, Iio Shouichiro, Ikeda Toshihiko

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY Vol. 229 ( 8 ) page： 968 - 977 2015.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy

This study simulates the flow through a small-scale open cross-flow hydraulic turbine and analyzes the turbine's performance. The simulation employs a two-dimensional particle method that was used for the simulation of a small-scale impulse-type hydraulic turbine in a prior study. Flow in the turbine is successfully simulated, with the simulated turbine performance showing good agreement with experimental measurements. The simulations also clarify that the deterioration in performance with increasing water flow rate is caused by the degeneration of the radially outward flow between the rotor blades.

DOI： 10.1177/0957650915592260

Web of Science

Scopus

Investigation of Blade Angle of an Open Cross-Flow Runner

Katayama, Y; Iio, S; Veerapun, S; Uchiyama, T

INTERNATIONAL JOURNAL OF TURBO & JET-ENGINES Vol. 32 ( 1 ) page： 65 - 72 2015.4

Language：English Publishing type：Research paper (scientific journal) Publisher：International Journal of Turbo and Jet Engines

The aim of this study was to develop a nano-hydraulic turbine utilizing drop structure in irrigation channels or industrial waterways. This study was focused on an open-type cross-flow turbine without any attached equipment for cost reduction and easy maintenance. In this study, the authors used an artificial indoor waterfall as lab model. Test runner which is a simple structure of 20 circular arc-shaped blades sandwiched by two circular plates was used The optimum inlet blade angle and the relationship between the power performance and the flow rate approaching theoretically and experimentally were investigated. As a result, the optimum inlet blade angle due to the flow rate was changed. Additionally, allocation rate of power output in 1st stage and 2nd stage is changed by the blade inlet angle.

DOI： 10.1515/tjj-2015-0005

Web of Science

Scopus

0210 Numerical Simulation of Jet Issued into Density-Stratified Fluid in a Cylindrical Tank

AOZASA Isao, UCHIYAMA Tomomi

The Proceedings of the Fluids engineering conference Vol. 2015 ( 0 ) page： _0210-1_ - _0210-5_ 2015

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

This study is concerned with the numerical simulation of the jet issued into two-layer density-stratified fluid in a cylindrical tank. Vortex in cell (VIC) method combined with an Immersed Boundary (IB) method is applied to the simulation. The upper and lower fluids are water and a NaCl-water solution, respectively, and the lower fluid is issued vertically upward from a nozzle on the bottom of the tank. The Reynolds number Re defined by the jet velocity and the nozzle diameter ranges from 95 to 1188, and the mass concentration of the NaCl-water solution is set at 0.02. The simulation highlights that the jet behavior relative to the density interface and the resultant mixing phenomena depend on Re. Such simulated results are confirmed to agree well with the experimentally visualized ones, demonstrating the validity of the present simulation method.

DOI： 10.1299/jsmefed.2015._0210-1_

CiNii Research

Development of a non-clogging micro-hydraulic turbine of propeller type

Uchiyama T., Nishida Y., Ide Y.

ICOPE 2015 - International Conference on Power Engineering 2015

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ICOPE 2015 - International Conference on Power Engineering

This study is concerned with the development of a hollow micro-hydraulic turbine excellent in foreign matter passage performance. The runner has a circular hollow around the central (rotating) axis so that foreign matter included in water can easily flow without blocking the turbine. The laboratory experiments are conducted to investigate the turbine performance. The guide vane successfully heightens the turbine efficiency. Though the maximum efficiency decreases with increasing the hollow ratio ϵ when ϵ>0.25, it remains unchanged when ϵ≤ 0.25. The hollow of the runner effectively heightens the passage performance of the polyester fibers entrained into the turbine. When employing the guide vane, the developed micro-hydraulic turbine of ϵ≥0.375 is not blocked by the fibers and maintains its function.

Scopus

402 Development of a Non-Clogging Micro-Hydraulic Turbine of Propeller Type

UCHIYAMA Tomomi, IDE Yukio, OKAYAMA Tomoko

The Proceedings of the Symposium on Environmental Engineering Vol. 2015.25 ( 0 ) page： 143 - 146 2015

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

This study is concerned with the development of a hollow micro-hydraulic turbine excellent in foreign matter passage performance. The runner has a circular hollow around the central (rotating) axis so that foreign matter included in water can easily flow without blocking the turbine. The laboratory experiments are conducted to investigate the turbine performance. Though the turbine efficiency decreases with increasing the hollow ratio e when ε>0.25, it remains unchanged when ε≤0.25. The hollow of the runner effectively heightens the passage performance of the polyester fibers entrained into the turbine. The developed micro-hydraulic turbine of ε≥0.375 is not blocked by the fibers and maintains its function.

DOI： 10.1299/jsmeenv.2015.25.143

CiNii Research

Numerical simulation of bubbly flow by an improved vortex in cell method

Uchiyama T., Yoshii Y., Chen B., Wang Z.

Advances and Applications in Fluid Mechanics Vol. 17 ( 1 ) page： 91 - 114 2015

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Advances and Applications in Fluid Mechanics

A simulation method for gas-liquid bubbly flows entraining small bubbles is proposed. It is based on the Vortex in Cell (VIC) method originally presented to simulate incompressible single-phase flows. The staggered grid discretization method and the vorticity correction method, which were proposed for the VIC method simulating single-phase flows by the authors’ prior study, are employed. The liquid velocity field is discretized with vortex elements, and the time evolution of the bubbly flow is simulated by calculating the behavior of each vortex element and the bubble motion through the Lagrangian approach. The proposed method is applied to the simulation of a bubble plume in a water tank to discuss the validity and applicability. Small air bubbles are released successively from the base of the tank, and their rise due to the buoyant force induces the water flow around them. The simulation at the starting period of the bubble release highlights that the rising bubbles induce vortex rings at their top and that a bubble cluster appears owing to the entrainment of the bubbles into the vortex rings. The rising velocity of the top of the bubbles is proportional to the square-root of the flowrate of the released bubbles, being consistent with the existing theoretical and numerical investigations. The simulation also demonstrates that the developed bubble plume having jet characteristics is successfully captured.

DOI： 10.17654/15-aafm-01701-091

Scopus

S0510402 Experimental Study on the Flow around a Circular Cylinder Mounted in Bubble Plume

UCHIYAMA Tomomi, ISHIGURO Yukihiro

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2015 ( 0 ) page： _S0510402- - _S0510402- 2015

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

This study explores the bubble plume around a circular cylinder in a water tank. Small gas bubbles with diameter of less than 0.06 mm are released from electrodes on the bottom of the tank by using the electrolysis of water. They induce the water flow with rising by the buoyant force. In such bubble plume, a circular cylinder with diameter D of 30 mm is mounted at an elevation of 6.5D above the electrodes. This study visualizes the bubbles and water flow around the cylinder and measures the bubble velocity distribution. The experiment elucidates the separated shear layers originating from the cylinder wall, their roll-up, and the bubble entrainment in the resultant large-scale eddies behind the cylinder.

DOI： 10.1299/jsmemecj.2015._s0510402-

CiNii Research

Numerical study on the flow and performance of an open cross-flow mini-hydraulic turbine Reviewed

Uchiyama, T, Uehara, S, Fukuhara, H, Iio, S, Ikeda, T

J. Power and Energy, Proc. IMechE Part A Vol. 229 ( 8 ) page： 968-977 2015

Numerical simulation of jet flow issued into density-stratified fluid by vortex in cell method

Shakouchi S., Shimada S., Uchiyama T.

Advances and Applications in Fluid Mechanics Vol. 17 ( 1 ) page： 115 - 134 2015

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Advances and Applications in Fluid Mechanics

This study proposes a numerical simulation method for a jet flow issued into a two-layer density-stratified fluid. The method is based on the Vortex in Cell method, which discretizes the vorticity field into vortex elements and computes the time evolution of the flow by tracing the convection of each vortex element using the Lagrangian approach. The proposed method is applied to simulate a jet flow, which was experimentally investigated in the authors’ prior study, so as to demonstrate the validity of the method. The simulation highlights that the jet behavior relative to the density interface depends on the jet Reynolds number and that it agrees well with the experimentally visualized one.

DOI： 10.17654/15-aafm-01701-115

Scopus

Numerical simulation of bubbly flow by vortex in cell method

Uchiyama Tomomi, Yoshii Yutaro

IUTAM SYMPOSIUM ON PARTICLE METHODS IN FLUID DYNAMICS Vol. 18 page： 138 - 147 2015

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Procedia IUTAM

A vortex in cell (VIC) method for bubbly flow is proposed. It computes the time evolution of the flow by calculating the behavior of the vortex element as well as the bubble motion with the Lagrangian approach. The proposed method is also applied to simulate a bubble plume to demonstrate the validity. In a tank containing water, small air bubbles are released from the base of the tank. The bubbles rise due to the buoyant force, inducing the water flow around them. The simulation for the plume at the starting period highlights that the rising bubbles induce vortex rings at their top and that a bubble cluster appears owing to the entrainment of the bubbles into the vortex rings. The rising velocity for the top of the bubbles is proportional to the square root for the flow rate of the released bubbles, being consistent with an existing theoretical investigation. The simulation also demonstrates that the developed bubble plume having jet characteristics is successfully captured.

DOI： 10.1016/j.piutam.2015.11.014

Web of Science

Scopus

ICOPE-15-1101 Development of a non-clogging micro-hydraulic turbine of propeller type

UCHIYAMA Tomomi, NISHIDA Yoshihiro, IDE Yukio

The Proceedings of the International Conference on Power Engineering (ICOPE) Vol. 2015.12 ( 0 ) page： _ICOPE-15- - _ICOPE-15- 2015

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

This study is concerned with the development of a hollow micro-hydraulic turbine excellent in foreign matter passage performance. The runner has a circular hollow around the central (rotating) axis so that foreign matter included in water can easily flow without blocking the turbine. The laboratory experiments are conducted to investigate the turbine performance. The guide vane successfully heightens the turbine efficiency. Though the maximum efficiency decreases with increasing the hollow ratio ε when ε>0.25, it remains unchanged when ε≦0.25. The hollow of the runner effectively heightens the passage performance of the polyester fibers entrained into the turbine. When employing the guide vane, the developed micro-hydraulic turbine of ε≧0.375 is not blocked by the fibers and maintains its function.

DOI： 10.1299/jsmeicope.2015.12._icope-15-_70

CiNii Research

Simulation of jet issued into two-layer density-stratified fluid by vortex in cell method combined with immersed boundary method

Aozasa I., Uchiyama T.

ASME/JSME/KSME 2015 Joint Fluids Engineering Conference, AJKFluids 2015 Vol. 1A 2015

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ASME/JSME/KSME 2015 Joint Fluids Engineering Conference, AJKFluids 2015

Jet flow issued into two-layer density-stratified fluid in a cylindrical tank is numerically simulated. Vortex in cell (VIC) method combined with an Immersed Boundary (IB) method, which is presented by the current authors, is applied to the simulation. The upper and lower fluids are water and a NaCl-water solution, respectively, and the lower fluid is issued vertically upward from a nozzle on the bottom of the tank. The Reynolds number Re defined by the jet velocity and the nozzle diameter ranges from 95 to 1188, and the mass concentration of the NaCl-water solution Co is set at 0 and 0.02. The simulation highlights that the jet behavior relative to the density interface and the resultant mixing phenomena depend on Re. Such simulated results are confirmed to agree well with the experimentally visualized ones, demonstrating the validity of the present simulation method.

DOI： 10.1115/ajkfluids2015-24394

Scopus

Numerical Simulation of Entrainment and Transport of Gas Bubbles by Vortex in Cell Method Invited Reviewed

Uchiyama, T. and Yoshii, Y

page： on USB flash drive 2011.7

Vortex Simulation for Bahavior of Solid Particles Falling in Air Reviewed

Yagami, H. and Uchiyama, T.

Proc. ASME-JSME-KSME Joint Fluids Engineering Conference 2011 page： on USB flash drive 2011.7

Vortex in Cell法による気泡流の数値シミュレーション Reviewed

内山知実，吉井佑太郎

日本機械学会論文集B編 Vol. 77 ( 778 ) page： 1301-1313 2011

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Papers - UCHIYAMA, Tomomi