1997 Fiscal Year Final Research Report Summary
Temperature elevation, streaming, and self-action in sound beams
| Project/Area Number |
08650063
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied physics, general
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| Research Institution | University of Electro-Communications |
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Principal Investigator |
KAMAKURA Tomoo Univ.of Electro-Communications, Professor, 電気通信学部, 教授 (50109279)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Nonlinear Acoustic / Ultrasonic beam / Self-action / Acoustic streaming / Ultrasonic heating |
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| Research Abstract |
When ultrasound is traveling down in a thermoviscous fluid, the sound energy is dissipated, and the fluid temperature in the beam is elevated. Inaddition of thus ultrasonic heating, bulk movement of the fluid is induced as acoustic streaming. The streaming carries away locally heated mass of the fluid downstream and reduces the temperature in the beam as cooling effect. Two physical phenomena of cooling effect by streaming and thermal self-action of sound beam in a viscous fluid have been investigated for the term of the present project. Sound energy losses due to viscosity and heat conduction in the fluid induce temperture elevation locally and streaming globally in the beams. The streaming carries forcibly away the heated mass of the medium and the temperature elevation is reduced. In a high viscous fluid, however, the streaming does not greatly build up because of the viscosity. As physical parameters such as sound speed depend on temperature in most fluids, sound beam changes its amplitude itself with irradiation time. A complicated but profitable numerical calculation scheme to solve simultaneously the basic hydrodyamic equations, heat transport equation, and wave equation, all the equations have individually temperature-dependent parameters, has been established using a finite difference method.
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