著者

金川 哲也

出版者

一般社団法人 日本物理学会

雑誌

大学の物理教育 (ISSN:1340993X)

巻号頁・発行日

vol.24, no.2, pp.72-76, 2018-07-15 (Released:2018-08-15)

参考文献数

2

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1.“工学科”での熱力学教育の問題点筑波大学理工学群工学システム学類は,機械,土木,建築,電気,情報などの工学分野を包含する,理工学部“工学科”なる表現が適切な学科である (以下,“工学科”).著者は“工学科”のう

著者

鮎貝 崇広 金川 哲也

出版者

日本工業出版

雑誌

超音波techno (ISSN:09162410)

巻号頁・発行日

vol.32, no.5, pp.50-53, 2020-09

著者

谷田部 貴大 金川 哲也 鮎貝 崇広

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.35, no.2, pp.356-364, 2021-06-15 (Released:2021-07-08)

参考文献数

33

被引用文献数

4

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Weakly nonlinear (i.e., finite but small amplitude) propagation of plane progressive pressure waves in compressible water flow uniformly containing many spherical gas bubbles is numerically investigated with a special attention to a drag force acting bubbles and translation of bubbles. The gas and liquid phases are flowing with initially independent velocities. Drag force and virtual mass force are introduced as interfacial momentum transports. Translation and spherically symmetric oscillations are considered as bubble dynamics. In this paper, under these assumptions, we numerically solve the KdVB (Korteweg-de Vries-Burgers) equation previously derived by ourselves (Yatabe et al., Phys. Fluids, 33 (2021), 033315) from basic equations based on a two-fluid model. The main results are summarized as follows: (i) The drag force acting on bubbles increases a dissipation effect of waves and drastically changes the phase and amplitude of waves. (ii) Although the translation of bubbles increases the nonlinear effect of waves, its contribution to waveform is quantitatively small. (iii) The effect of the drag force decreases with decreasing the initial void fraction and with increasing the initial bubble radius. That of the translation decreases with decreasing the initial void fraction, and is almost independent of the initial bubble radius. (iv) The spatiotemporal evolution of two type of dissipation effects (i.e., dissipation terms) due to the acoustic radiation and to the drag force is different tendency.

著者

加賀見 俊介 金川 哲也

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.35, no.2, pp.346-355, 2021-06-15 (Released:2021-07-08)

参考文献数

48

被引用文献数

4

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Weakly nonlinear focusing of quasi-planar ultrasound in a liquid nonuniformly containing many spherical microbubbles is theoretically investigated with a special focus on a thermal conduction at the bubble-liquid interface toward medical applications such as tumor coagulation by HIFU. Based on the previously derived Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation by our group (Kanagawa, J. Acoust. Soc. Am., 137 (2015), 2642), we derived a KZK equation newly incorporating the viscosity of bubbly liquids and the thermal conduction at the bubble-liquid interface by utilizing the energy equation inside bubble. As a result, two types of dissipation term were discovered in the resultant KZK equation: one is the second-order partial derivative term owing to the viscosity of bubbly liquids and the liquid compressibility and the other is a term without differentiation owing to the thermal conductivity. We found that the thermal conduction strongly contributes the dissipation effect.

著者

平 久夫 金川 哲也

出版者

京都大学

雑誌

数理解析研究所講究録 (ISSN:18802818)

巻号頁・発行日

no.1946, pp.118-124, 2015-04

著者

前田 泰希 金川 哲也

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.34, no.1, pp.140-147, 2020-03-15 (Released:2020-04-02)

参考文献数

20

被引用文献数

2

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Weakly nonlinear propagation of plane pressure waves in a flowing water uniformlycontaining many spherical microbubbles is theoretically investigated. At the initial state, the gas and liquid phases have different flow velocity distributions as a small nonuniform effect in bubbly flows. The basic equations based on a two-fluid model are utilized to describe velocity distributions of gas and liquid phases. By using the method of multiple scales and the determination of size of three nondimensional ratios, we can systematically derive two types of nonlinear wave equations describing long-range propagation of waves. i.e., the Korteweg-de Vries-Burgers (KdVB) equation and the nonlinear Schrödinger (NLS) equation with variable coefficients. As a result, initial velocity distributions affect an advection effect of waves induced by a relative velocity between gas and liquid phases and a moving bubble.

著者

圷 亮輔 慶本 天謹 金川 哲也 内山 祐介

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.34, no.1, pp.166-179, 2020-03-15 (Released:2020-04-02)

参考文献数

28

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Two types of weakly nonlinear propagations of plane progressive pressure waves in an initially quiescent compressible liquid uniformly containing many spherical gas bubbles are theoretically investigated. The treatment of two types of propagations corresponds to an extension of our previous result (Yoshimoto & Kanagawa, Jpn. J. Multiphase Flow, 33 (2019), 77) to a generic form. The main assumptions are as follows: (i) The incident wave frequency is much larger than an eigenfrequency of single bubble oscillations; (ii) The compressibility of the liquid phase, which has long been neglected and induces the high speed propagation mode, is considered; (iii) The wave propagates with a large phase velocity exceeding the speed of sound in pure water. From the method of multiple scales with two types of appropriate choices of three nondimensional parameters, we can systematically derive two types of nonlinear Schrödinger (NLS) equations with some correction terms in a unified way. These two equations can describe high-speed propagation of pressure waves in compressible bubbly liquids.

著者

鮎貝 崇広 金川 哲也

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.34, no.1, pp.158-165, 2020-03-15 (Released:2020-04-02)

参考文献数

13

被引用文献数

7

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Oscillation of gas bubbles in a bubbly liquid induces dissipation and dispersion effectsof waves into a nonlinear evolution of pressure waves. Long-range propagation of pressure waves with a moderately small amplitude is described by the KdV-Burgers (KdVB) equation. This paper numerically solves the KdVB equation via a spectral method to predict the nonlinear evolution of waves in bubbly liquids. Focusing on the waveform, and the nonlinear, dissipation and dispersion terms, the following results are obtained: (i) An initially sinusoidal waveform satisfying a periodic boundary condition is firstly distorted due to the nonlinear effect; (ii) Wave distortion is suppressed by increasing the dissipation and dispersion effects; (iii) A break-up due to the dispersion effect appears; (iv) A balance between the nonlinear and dispersion effects is accomplished and then a pulse wave satisfying a feature of soliton is formed. As a result, the initial bubble radius and the initial void fraction strongly contribute the dissipation and dispersion effects, respectively.

著者

亀井 陸史 金川 哲也

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.34, no.1, pp.148-157, 2020-03-15 (Released:2020-04-02)

参考文献数

20

被引用文献数

2

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This study theoretically clarifies an effect of the liquid viscosity and the thermal conductivity on weakly nonlinear propagation of pressure waves in a liquid containing many spherical microbubbles. As in our preceding paper (Kamei et al., J. JSCE, Ser. A2, 75 (2019), 499) focusing on a long wave, by the use of the method of multiple scales, a nonlinear Schrödinger equation describing the long-range propagation of an envelope wave of short carrier wave is derived from the basic equations incorporating the liquid viscosity and the thermal conductivity. As a result, as in our preceding long wave case, the liquid viscosity and the thermal conductivity affect the dissipation effect, and a nonlinear effect in the adiabatic process decreases in comparison with the previous study (Kanagawa et al., J. Fluid Sci. Technol., 6 (2011), 838). On the other hand, unlike in our preceding long wave case, a dispersion effect in the adiabatic process decreases in comparison with the previous study.

著者

亀井 陸史 鮎貝 崇広 金川 哲也

出版者

公益社団法人 土木学会

雑誌

土木学会論文集A2(応用力学) (ISSN:21854661)

巻号頁・発行日

vol.75, no.2, pp.I_499-I_508, 2019 (Released:2020-02-06)

参考文献数

34

被引用文献数

4

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多数の球形微細気泡を含む水中において, 波長の長い平面圧力波の弱非線形伝播に粘性と熱伝導性が与える影響を理論的に調べる. 多重尺度法を用いて, 粘性と熱伝導性を考慮した気泡流の基礎方程式系から低周波数の長波の長距離伝播を記述する KdV–Burgers 方程式を導いた. 気泡流全体の粘性と熱伝導性を無視した先行研究(金川ら, 機論 B, 76, 1802, 2010) との対比から, 液相粘性と熱伝導性の影響は散逸性のみに現れ, 気泡内気体の熱力学的過程が非線形, 散逸, 分散の全性質に影響を与えることがわかった. さらに, KdV–Burgers 方程式を数値的に解き, 非線形性, 分散性の順に波形に対して性質が発現することがわかった. 本研究と先行研究の数値解を比較すると, 本研究の方が散逸性と分散性が強いことが波形からも確認できた.

著者

金川 哲也

出版者

筑波大学

雑誌

若手研究(B)

巻号頁・発行日

2014-04-01

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ポンプの中を流れる水中において、しばしば、衝撃波という「危険な」波が形成される。これを、ソリトンという「安全な」波に変換できれば、ポンプの損傷を抑制することが可能となる。本研究の目的は、この革新的技術開発のための理論的基盤の創成にある。気泡流中において、水中音速1,500 m/sを超えて伝播するという、水の圧縮性の効果が招く高速伝播圧力波を用いて、ソリトン遷移した衝撃波をポンプ内から速やかに逃がすという着想に基づき、高速伝播圧力波の非線形伝播の理論解析および数値解析を行った。今後、本理論の実験的検証研究や、次世代のポンプへの実装を目指した産学連携研究といった、さらなる進展が期待されるだろう。