具斜面雙橡膠水下吸音材設計與分析

The Design and Analysis for Underwater Acoustic Absorber of Double Rubber with Inclined Plane

賴柏辰(Po-Chen Lai)

指導教授 ： 黃心豪

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202970

摘要

本文以週期性排列空隙水下吸音材為基礎，考慮雙橡膠在不同斜面角度下對吸音係數的影響，將斜面雙橡膠的概念和週期性排列空隙水下吸音材相結合，提出一種新的水下吸音材設計方向，來提升有效吸音頻寬。本文首先對幾何參數進行討論，得到一組在四千到九千赫茲間具有吸音係數大於0.7的單橡膠水下吸音材參數，加入斜面雙橡膠概念後使吸音係數大於0.7的頻寬拓展至三千赫茲到九千赫茲。提出等效模型能計算出吸音係數峰值所在的頻率，降低參數討論時的繁瑣性，此等效模型亦能用於斜面雙橡膠水下吸音材設計。考量到水下吸音材在受靜水壓後造成的形變和應力集中問題對具有最佳有效吸音頻寬的模型進行調整，雖然有效吸音頻寬相較未調整前略微變窄，但吸音材的應力集中與形變情形有所降低，且整體有效吸音頻寬相較單橡膠設計仍有拓寬。最後將調整後的斜面雙橡膠吸音材設計從二維模型轉變為三維模型，考慮不同空隙形狀，以甜甜圈形的空隙和二維結果最為相近。同時聲源以不同角度入射吸音材探討吸音性能的改變，以更符合實際使用場景。本文提出一種水下吸音材設計的新思路，具斜面雙橡膠水下吸音材能夠提升低頻的吸音性能，拓寬水下吸音材的有效吸音頻寬。同時考慮到實際應用的各種情況對設計的吸音材進行討論，說明本文提出的設計具有實際應用的潛力。

關鍵字

水下吸音材 ； 等效模型 ； 斜面雙橡膠設計 ； 靜水壓 ； 斜向入射

並列摘要

Based on the underwater absorber with periodic voids. We consider the influence of absorption coefficient by double-rubber with different inclined plane angles. This paper combines the concept of double-rubber with inclined plane and periodic voids underwater absorber, proposing a new underwater absorber design. The design improve the effective sound absorption bandwidth. In this paper, the geometric parameters are first discussed, and a group of geometric parameters with absorption coefficient greater than 0.7 between 4kHz and 9kHz are obtained. Combing the concept of double-rubber with inclined plane, the bandwidth of absorption coefficient greater than 0.7 is enlarged that the bandwidth is between 3kHz and 9kHz. The frequency of the absorption coefficient peaks can be calculated through the effective model, which can reduce the complexity of parameters discussion. This effective model can also be used for the design of double rubber underwater absorber with inclined plane. Considering the influence of hydrostatic pressure for the deformation and stress concentration of the underwater absorber, the model with widest effective absorption bandwidth would be adjusted. Although the absorption bandwidth is slightly narrower than before the adjustment, the stress concentration and deformation situation are reduced. The overall absorption bandwidth is still wider than the single rubber design. Finally, the adjusted design of the double-rubber absorber with inclined plane was transformed from two-dimensional model to three-dimensional model. Considering different void shapes, the absorption coefficient of doughnut-shaped voids is the most similar to the two-dimensional result. The change of absorption coefficient by oblique sound incidence is also considered. This paper proposes a new idea for the design of underwater absorber. The design of double-rubber with inclined plane can improve the low frequency absorption performance. At the same time, the absorber is in consideration of various situations of application, which indicates that the design proposed in this paper has the potential to be used as an underwater absorber.

並列關鍵字

underwater absorber ； effective model ； double rubber with inclined plane ； hydrostatic pressure ； oblique incidence

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