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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/53395

Title: 具加強肋幾何結構之水下聲場輻射研究
Study on Underwater Acoustic Radiation of a Geometric Structure with Reinforced Ribs
Authors: Tseng, Wan-Yi
Contributors: NTOU:Department of Marine Engineering
Keywords: 加強肋;減振;有限元聲學;聲場輻射
Reinforced Ribs;Reducing Vibration;Finite Element Method;Acoustic Radiation
Date: 2019
Issue Date: 2020-07-02T08:21:06Z
Abstract: 本文利用有限元素法計算水下載具安裝加強肋之水下聲場輻射現象。水下載具之設計需考量體積及重量配置,而加強肋能達到在增加最小質量之狀況下增加結構整體剛性之目的,除此之外亦能提升整體結構抗壓強度並增加下潛深度,且具備抑制振動之效果。然而,結構體受到外力激振後,連動周圍介質引發結構耦合特性,進而產生結構噪音及聲場輻射音,因此若要探討水下聲場輻射,必須探討結構體與介質之流固耦合現象。本文以有限元素法為基礎,計算流固耦合問題,並計算聲結構產生之水下聲場輻射。由於離散技巧所建構之剛性矩陣不同:有限元素法為系統或稀疏矩陣、邊界元素法為全矩陣(或稱滿矩陣),其計算結果有限元素法之計算效率優於邊界元素法。當分析不規則幾何時,容易產生數值不穩定之現象。當結構幾何安裝加強肋時,加強肋凸出處與結構體交接處,進行聲場網格建置時,結構網格及聲場網格之耦合面無法完全貼合,造成邊界產生不連續性,導致計算結果有所誤差。本文以整體結構向外增加微小距離之方式創造聲場網格,使結構網格及聲場網格之耦合面得以完全貼合,保持邊界條維持連續性。最後分別比較理論與數值解,驗證此方法具有其可行性與準確性。其計算結果與求解流程具備工程應用之價值。
In this thesis, we use the finite element method to solve the underwater acoustic radiation of underwater vehicles with reinforced ribs. The designs of underwater vehicles have to take into account the limit of space and weight, while the reinforced ribs can achieve the purpose of increasing the stiffness of the structure with minimal mass. However, after the structure is excited by an external force, it causes the coupling characteristics and acoustic radiation. Therefore, it is necessary for exploring the underwater acoustic radiation to investigate the fluid-solid interaction. We use the finite element method to solve the problem of fluid-solid interaction and the underwater acoustic radiation. Because of the different solving matrix, the computation efficiency of the finite element method is better than the boundary element method. When the structure is installed with reinforced ribs, the coupling faces of the structure and the acoustic cannot be completely matched. It causes that the boundary is discontinuous and errors in the calculation results. In this thesis, we add a small distance of the structure to create the acoustic mesh. It makes the coupling faces of the structural mesh and the acoustic mesh completely fit, and keep the continuity of boundary. Finally, we compare the theoretical and numerical solutions to verify the feasibility and accuracy of this method. The numerical results and the solution flow have the value in engineering application.
URI: http://ethesys.lib.ntou.edu.tw/cgi-bin/gs32/gsweb.cgi?o=dstdcdr&s=G0010766012.id
Appears in Collections:[輪機工程學系] 博碩士論文

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