基於傳遞矩陣與有限元素法分析具傾斜雙橡膠之水下吸音材聲學性能

Abstract

近年水下載具研究興盛，根據研究顯示，台灣本土也有自製水下載具的能力，因此對於水下聲學隱形匿蹤有極大的需求。本研究欲設計一具傾斜雙橡膠之水下聲學超穎材料，主要利用斜面的波型轉換機制增加聲波衰減的性能，另外結構結合了週期性空氣腔與固體嵌入物等吸音機制，達成一具寬頻吸音的水下聲學超穎材料。研究中分別討論了三種形式的傳遞矩陣方法，分別為聲學馬賽克、均勻等效的週期性空氣腔以及均勻等效的週期性固體嵌入物，用以預測吸音係數，並與有限元素法模擬進行相互比較。接著，研究探討了三種不同吸音機制的物理意義，結果顯示傾斜雙橡膠的設計有助於提升有效吸音頻寬，並將有效吸音頻寬往低頻移動。最後在探討實際水下應用時，考慮了不同背襯條件、斜向入射以及三維模型，說明本研究提出之水下聲學超穎材料具有可行性。

In recent years, research on underwater vehicles has thrived. According to studies, Taiwan also possesses the capability to manufacture homemade underwater vehicles, creating a significant demand for underwater acoustic stealth technology. This study aims to design an underwater acoustic metamaterial with inclined dual rubber components. The primary focus is on enhancing the performance of sound wave attenuation through the mechanism of inclined wave conversion. Additionally, the structure incorporates absorbing mechanisms such as periodic air cavities and solid inclusions to achieve a broadband absorption underwater acoustic metamaterial. The study discusses three forms of transfer matrix methods: acoustic mosaic, uniformly equivalent periodic air cavities, and uniformly equivalent periodic solid inclusions. These methods are employed to predict absorption coefficients and are compared with finite element method simulations. Finally, the physical meanings of three different absorption mechanisms are explored. The results indicate that the design of inclined dual rubber components contributes to an increased effective absorption bandwidth, shifting it towards lower frequencies. In simulations for practical underwater applications, considering different backing conditions, oblique incidence, and three-dimensional models, the study demonstrates the feasibility of the researched underwater acoustic metamaterial.