A boundary element analysis on acoustic dissipation by wall visco-thermal boundary layer
Project/Area Number |
10650596
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Research Category |
Grant-in-Aid for Scientific Research (C)
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Allocation Type | Single-year Grants |
Section | 一般 |
Research Field |
Architectural environment/equipment
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Research Institution | Kanagawa university |
Principal Investigator |
TERAO Michihito Kanagawa University, Faculty of engineering, Professor, 工学部, 教授 (40013198)
|
Project Period (FY) |
1998 – 1999
|
Project Status |
Completed (Fiscal Year 1999)
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Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
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Keywords | wall visco-thermal boundary layer / acoustic dissipation / substructure technique / boundary element numerical approach / high percision experiment / non-circular aperture / aperture inertance / aperture resistance / 開口部音響散逸 / 吸音力予測 / ヘルムホルツ型共鳴器 / 壁面熱伝導境界層 / 壁面粘性境界層 / 音場数値解析 / 境界要素法 / 物理的検証実験 |
Research Abstract |
On acoustic energy dissipation at wall surfaces, especially at the solid surfaces of the apertures of resonators of Helmholtz type, the viscosity and thermal conductance there plays the leading role. By using the Stokes theory for the viscous mode and the Kirchhoff theory for the thermal mode, explicit expressions can been given for the acoustic resistance of the aperture of simple shape such as a long round tube. However for n neck of general shape with finite length, we have to solve implicit relationships between acoustic mode wave and the visco-thermal boundary layer. We employed a boundary element numerical approach along with the substructure techniques for the acoustic mode fields, and implemented a computer code to combine the acoustic mode and the visco-thermal mode through the effective acoustic mode admittance for the visco-thermal boundary layer. This admittance was derived from the Stokes and Kirchhoff theories, and includes the Laplacian of the acoustic pressure over the acoustic mode boundary. We took a finite difference approach for the Laplacian operation by employing the constant boundary element. To investigate the effectiveness of the numerical simulation, we conducted a series of numerical simulations and experiments for the dissipation factors of slit resonators, and compared the results. In the experiments, rigid specimens of highly precise dimensions are used. Consequently, the agreement between the dissipation factor by the numerical simulation and that by the experiment was excellent, as far as boundary element dimension was 0.1 mm or finer. To reduce the requirement of this fine element size, the use of a third order approximation element is under investigation.
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Report
(3 results)
Research Products
(20 results)