MACHINE VIBRATION INDUCED UNDERWATER ACOUSTIC RADIATION

本文以偶合的有限元素／邊界元素法，來處理結構噪音傳播與水中噪音輻射中彈性結構物與流體之互制問題。爲改進船舶之適居性與隱匿性，各式船舶均需要靜音之條件，其中由船體熱運動所輻射出之空氣與水中音是主要的音源成分，因此結構音特性之估算在設計一艘安靜船是很重要的一件事情。利用本文之方法對船體承受激振力後濕表面之壓力分布及各部振動反應可以分析，進一步亦可評估探討船體表面之複數功率、輻射功率及阻抗功率。文中舉兩個數值實例，一是浸在水中的球殼受均勻簡諧內壓、及別致沲于水面之機艙結構模型受馬達激振，分別計算其表面聲壓、法向速度、表面複數功率、輻射功率、阻抗功率、表面振動位移響應及在遠場的水中輻射聲型，將此數值解與實驗量測值比較，顯示建立之預估模式可信。另者，對主推進引擎加裝彈性墊對水下噪音輻射之降低效果，亦加以探討。

關鍵字

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並列摘要

A coupled FEM/BEM for solving fluid-structure interaction problem in structure-borne noise propagation and underwater acoustic radiation is present in this paper. In order to improve the habitability and stealth low noise condition is required in various types of ships. One of the dominant components is the radiated airborne and underwater noise caused by ship hull vibration. Accordingly, the estimation of structure-borne sound characteristics of a ship is important in the design of a quieter ship-structure. The hull vibration response and pressure distribution on the wetted surface of a ship subjected to excitation sources can be analyzed by utilizing the developed method. Further discussions on the evaluation of surface complex power, radiation and reactance power have been conducted. Two cases were studied, a submerged spherical shell subjected to a uniformly harmonic pressure excitation and a scale model of engine room structure subjected to machine excitations, to illustrate the applications of the analytical model. The surface pressure, the normal velocity on the wetted surface ,the surface complex power, the radiation power, the reactance power, the vibrational displacement and the radiated underwater sound pattern have been computed. Comparison of the predicted results and that by measurement indicates that the numerical model is creditable. In addition, the effect on underwater acoustic radiation at the elastic mounts for the engine is discussed.

並列關鍵字

fluid-structure interaction ； coupled FEM/BEM ； radiation pattern

國際替代計量

MACHINE VIBRATION INDUCED UNDERWATER ACOUSTIC RADIATION

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