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博碩士論文 etd-0623104-103951 詳細資訊
Title page for etd-0623104-103951
論文名稱
Title
全向性聲源自具非均質沉積層之粗糙海床上平均反射場問題之研究
Mean-field reflection of omni-directional acoustic wave from rough seabed with non-uniform sediment layers
系所名稱
Department
畢業學年期
Year, semester
語文別
Language
學位類別
Degree
頁數
Number of pages
94
研究生
Author
指導教授
Advisor
召集委員
Convenor
口試委員
Advisory Committee
口試日期
Date of Exam
2004-06-14
繳交日期
Date of Submission
2004-06-23
關鍵字
Keywords
非均質沉積層、反射、平均反射場、計算聲學、線聲源、散射問題、點聲源、全向性聲源、粗糙海床、聲波
rough seabed, Line source, non-uniform sediment layers, Point source, scattering, Mean-field, reflection, acoustic wave
統計
Statistics
本論文已被瀏覽 5696 次,被下載 1387
The thesis/dissertation has been browsed 5696 times, has been downloaded 1387 times.
中文摘要
本研究在於探討全向性聲源於具密度與聲速連續變化沉積層之粗糙海床上平均反射場問題。延續自Liu, Wang, Tasi and Chu (2003) 有關平面聲波入射具彈性底床與非均質沉積層之粗糙海床上平均反射場問題之研究,將沉積層密度與聲速分別以廣義指數函數變化以及三種不同聲速分佈,常數、~$k^2$-linear、~inverse-square~型態分佈來表示,而本論文將平面聲波改以全向性聲源,來探討粗糙海床上平均反射場問題之研究。全向性聲源與平面聲波之差異在於全向性聲源波譜中包含所有的波數域,而平面聲波僅是波數域中某一方向分量,故可預期全向性聲源反射場將會更複雜。另外,解決粗糙界面問題的方法是引用~Kuperman~and~Schmidt~(1989)~所發表,以邊界攝動法~(boundary perturbation method)~的理論,求解粗糙界面散射問題中平均反射場。本研究與過去研究最大不同處,是建立一個符合實際海洋作業環境需求的全向性聲源於具非均質沉積層之粗糙海床上平均場反射場問題之研究。在本文的結果中,我們利用不同的海床粗糙度、沉積層密度與聲速連續變化、聲波頻率、沉積層厚度等相關參數,來模擬及分析整個平均反射場。並將所得之結果利用~OASES~聲學軟體加以驗證,以確定所得之結果之正確性。
Abstract
Omni-directional acoustic wave source interactions with a rough seabed with a continuously varying density and sound speed in a fluid-like sediment layer. The acoustic properties in the sediment layer possess an exponential type of variation in density and one of the three classes of sound speed profiles, which are constant,~$k^2$-linear, or inverse-square variations. Analytical solution of mean field. The mean field reflection coefficients corresponding to the aforementioned density and sound speed profiles for various frequencies, roughness parameters, are numberically generated and analyzed. Physical interpretations are provided for various results. This simple model characterizes two important features of sea floor, including seabed roughness, sediment inhomogenieties, therefore, provide a canonical analysis in seabed acoustics.
目次 Table of Contents
第一章 緒論
 1.1 研究主題與研究動機
 1.2 文獻回顧
 1.3 研究方法
 1.4 論文範疇
第二章 理論模式
 2.1 簡介
 2.2 聲波方程式
  2.2.1 均勻介質
  2.2.2 非均勻介質
  2.2.3 整理
 2.3 聲波方程式之解
  2.3.1 均勻介質
  2.3.2 非均勻介質
  2.3.3 整理
 2.4 邊界條件
  2.4.1 平滑界面
  2.4.2 粗糙界面
 2.5 線聲源
 2.6 結語
第三章 基準驗證
 3.1 OASES計算聲學軟體介紹
  3.1.1 OAST模組介紹
  3.1.2 OASR模組介紹
 3.2 光滑界面反射場之結果驗證
  3.2.1 層化性質之驗證
  3.2.2 聲場圖之驗證
 3.3 粗糙理論結果之驗證
 3.4 結語
第四章 反射場分析
 4.1 平滑界面之反射場分析
  4.1.1 點聲源
  4.1.2 線聲源
 4.2 粗糙界面之平均反射場分析
  4.2.1 粗糙面效應
 4.3 結語
第五章 結論與建議
 5.1 結論
 5.2 建議
參考文獻 References
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[3] Epstein, P., 1930. Reflections of waves in an inhomogenous absorbing medium. Proc. Natl. Acad. Sci. USA 16, 627.
[4] Goff, J.A. and Jordan, T. 1988. Stochastic modeling of seafloor morphology: Inversion of Sea Beam data for second-order statistics. J. Geophys. Res. 93, 13, 589-13,608.
[5] Hamilton, E.L., 1980. Geoacoustic modeling of the sea floor. J. Acoust. Soc. Am., 68, 1313–1340.
[6] Ivakin, A.N., Lysanov, P.,1981.Theory of underwater sound scattering by random inhomogenieties of the bottom. Sov. Phys. Acoust. 27, 61-64.
[7] Kuperman, W.A. and Schmidt, H.1989. Self-consistent perturnation approach to rough surface scattering in stratified elastic media. J. Acoust. Soc. Am., 86, 1511-1522.
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[9] Liu, J.-Y., Shyue, S.-W., Huang, C.-F., 2000. Coherent reflection of acoustic plane wave from rough interfaces in a stratified random fluid medium. J. Marine Science and Technology 8 (2), 90-100.
[10] Liu, J.-Y., Huang, C.-F.,2001. Acoustic plane-wave reflection from a rough surface over a random fluid half-space. Ocean Enging
[11] Miklowitz, J., 1978. The Theory of Elastic Waves and Waveguides. North-Holland, Amsterdam.
[12] Ranz-Guerra, C. and Carbo-Fite, R., 1893. Impulse of sediment laters with Variable density gradients. in Acoustics and the Sea Bed. Bath U.P., Bath, England.
[13] Liu, J.Y., Huang, C.F., 2001, Acoustic planewave scattering from a rough interface over an inhomogeneous transition fluid layer, Ocean Engineering, Vol. 28, No. 6, 603-619.
[14] Liu, J.Y., Tsai, S.H., Wang, C.C., Chu, C.R., Acoustic wave reflection from a rough seabed with a continuously varying sediment layer overlying an elastic basement, J. Sound and Vibration (in press).
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[17] Robins, A.J. 1993. Exact solutions of the Helmholtz equation for plane wave propagation in a medium with variable density and sound speed. J. Acoust. Soc. Am. 93(3), 1347– 1352.
[18] Robins, A.J. 1994. Generation of shear and compression waves in an inhomogeneous elastic medium. J. Acoust. Soc. Am. 96(3), 1669–1676.
[19] Rutherford, S.R, and Hawker, K.E.,1978.Effect of density gradients on bottom reflection loss for a class of marine sediments. J. Acoust. Soc. Am., 63, 750-757.
[20] Tolstoy, D.J., Frisk, G., 1991. Plane-wave reflection from a random fluid half-space. J.Acoust. Soc. Am. 90, 2751-2756.
[21] Tolstoy, I., 1963. The theory of waves in stratified fluids including the effects of gravity and rotation. Rev. Mod. Phys., 35, 207–230.
[22] Tolstoy, I., 1965. Effects of density stratification on sound waves. J. Geophys. Res., 70(24), 6009–6015.
[23] Williams, A.O. and MacAyeal, D.R., 1979. Acoustic reflection from a sea bottom with linearly increasing sound speed. J. Acoust. Soc. Am., 66, 1836–1841.
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[25] Yamamoto, T., 1996. Geoacoustic properties of the seabed sediment cirtical to acoustic reverberation at 50 to 500 Hz: a preliminary data set. J. Acoust. Soc. Am. Suppl. 1, 85, S86.
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