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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/48355

Title: 應用多層三明治結構於流固耦合問題
Application of Multi-layer Sandwich Structures on the Fluid-Structure Interaction problems
Authors: Lin, Jhih-Yu
林芝妤
Contributors: 國立臺灣海洋大學:輪機工程學系
Keywords: 三明治結構;阻尼;減振
Sandwich Structure;Damping;Reducing Vibration
Date: 2017
Issue Date: 2018-08-22T03:40:12Z
Abstract: 本文探討多層三明治結構及不同幾何設計下降低水下載具之聲場輻射問題。由於水下噪音及水下幾何設計減振一直都是海洋工程中非常重要之議題。水下振動噪音不同於一般空氣中機械減振的方法,其原因在於水下結構體幾何參數相依於水下流體而產生藕合。因此本文將探討多層三明治結構於水下結構物和水下結構物幾合之聲場輻射驗證。由於三明治結構組成至少包含拘束層與阻尼層,其中拘束層主要增加結構剛性而阻尼層則增加結構阻尼。當水下結構物幾何厚度增加,其物理特性會增加結構鋼性進而改變系統動態響應,其位移頻率響應峰值會往高頻方向平移,顯示利用三明治結構減振具有降低結構之振動量特性。當應用三明治結構於水下潛體,其結構體遭受外力動態負載產生變形,阻尼層中的黏彈性材料會將其能量耗損並轉換成熱能,進一步降低水下載具因為振動而產生的水下聲場輻射。因此本文利用有限元素法計算水下結構物之自然模態,然後進一步使用水下潛體之自然模態與邊界元素法進行藕合。為了驗證本文數值模式之準確性,分別與相關參考文獻進行相關數值計算比較。由數值結果證明,本文提出之三明治減振設計有效抑制結構體遭受外力動態負載產生之響應,進一步驗證水下聲場輻射響應,三明治減振特性有效抑制結構耦合產生之聲場輻射響應。因此,本研究之數值結果具有其工程設計價值與應用。
In this thesis, we apply the multi-layer sandwich structure with different geometric design to reduce the radiation noise from submerged structure. Recently, it is a very popular issue for under water noise and under water geometric design in the ocean engineering. Because the vibration and radiation of the submerged structure are different from those in air, it is very difficult to deal with the coupling of the response of structure and fluid. Therefore, we propose the multi-layer sandwich structure and geometrical structure to verify the radiation noise under water. The sandwich structure includes at least two types of material with the passive constrained layer (PCLD) and viscosity damping layer, and properties of PCLD and viscosity damping layer increase the stiffness and damping of structure, respectively. When the thickness of submerged structure increases, the physical property of the structure stiffness will increase and the system dynamic response will be change, the displacement frequency response peak translate to high frequency. It shows the sandwich structure can reduce the vibration of the structure. When we apply the sandwich structure on submerged structure, the structure is subjected to the dynamic loading and deformed, the viscoelastic material dissipated energy and conversing kinetic energy to thermal energy; then, to reduce the vibration from the submerged structure further avoid the radiation noise. Therefore, in this thesis we used FEM solving the vibration natural modes (VNM), and applied the VNM for the displacement expansions and coupling with BEM to compute the submerged structural responses. In order to verify the numerical accuracy and stability, we compared numerical solutions with analytical solutions. The results are shown that the present method reduced vibration efficiency and reduced sound radiation efficiency. Hence, the numerical results have value and its engineering application.
URI: http://ethesys.lib.ntou.edu.tw/cgi-bin/gs32/gsweb.cgi?o=dstdcdr&s=G0010466001.id
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/48355
Appears in Collections:[輪機工程學系] 博碩士論文

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