한국음향학회지 (The Journal of the Acoustical Society of Korea)

  • 제38권1호
  • /
  • Pages.67-72
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  • 2019
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  • 1225-4428(pISSN)
  • /
  • 2287-3775(eISSN)
한국음향학회 (The Acoustical Society of Korea)
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소형화된 헬름홀츠 공진기를 이용한 수중 반향음 감소해석 모의실험

Simulation of underwater echo reduction using miniaturized Helmholtz resonators

  • 박성준 (홍익대학교 기계시스템디자인공학과) ;
  • 김제도 (홍익대학교 기계시스템디자인공학과)
  • 투고 : 2018.11.06
  • 심사 : 2019.01.25
  • 발행 : 2019.01.31
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초록

본 연구에서는 파장보다 작은 구조물로 이루어진 음향메타물질을 이용하여 소형화된 헬름홀츠 공진기의 반향음 감소 성능예측 연구를 진행하였다. 본 논문에서 제안된 헬름홀츠 공진기는 수중 환경과 임피던스 차이가 큰 공기구조물로 형성하였다. 다중물리 유한요소 시뮬레이션 패키지를 이용하여 수중 음향학적 분석을 진행한 결과 수중 반향음의 감소가 예상되었고 헬름홀츠 공진기 입구의 공간 압축(space coiling) 정도와 내부 체적의 폭에 따라 주파수 특성을 제어할 수 있었다. 기본적인 헬름홀츠 공진기는 약 10,000 Hz 이상에서 최대 7 dB의 반향음 감소 효과를 보였으나 공간 압축 메타물질을 이용한 초소형 헬름홀츠 공진기는 약 5,000 Hz 이상에서 최대 14 dB의 반향음 감소가 나타났다. 추가적으로 헬름홀츠 공진기의 내부 체적을 제어하여 주파수 특성이 변화하는 것을 확인하고 공간압축 비율이 서로 다른 공진기를 조합함으로써 광대역 반향음 감소 효과를 얻을 수 있었다. 본 연구를 통해 수중 환경에서 공기구조물을 이용한 소형화된 헬름홀츠 공진기의 성능을 연구하였으며 반향음 감소 효과는 효과적인 스텔스 기술을 구현할 수 있을 것으로 기대된다.

In this study, we investigate the echo reduction performance of miniaturinzed Helmholtz resonators using smaller than wavelength acoustic metamaterial structures. The Helmholtz resonators are formed using air structures which exhibit large impedance mismatch with the surrounding underwater environment. Using the multi-physics software package, we find that significant reduction in the sonar signature is expected and frequency tailoring is possible by controlling the degree of space coiling and inner volume of the resonators. We find that for the basic Helmholtz resonators, up to 7 dB reduction in echo is expected at 10,000 Hz while when the miniaturized Helmoholtz resonators are used, up to 14 dB reduction in echo is expected at 5,000 Hz. In addition, frequency tailoring is demonstrated by varying the internal volume of the Helmholtz resonators and broadband characteristic is shown using superposition of various degree of space coiled structures. Through this study we investigate the effectiveness of the miniaturized Helmholtz resonators formed using air structures and the echo reduction results show promisses in the application of achieving underwater stealth.

키워드

GOHHBH_2019_v38n1_67_f0001.png 이미지

Fig. 1. Conceptual diagram of the miniaturized Helmholtzr esonator applied on the submarine hull.

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Fig. 2. The 2D simulation model of the underwater Helmholtz resonators. (a) the basic Helmholtz resonator model. (b), (c) miniaturized Helmholtz resonator models using various degree of space coiling acoustic metamaterial.

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Fig. 3. Comparison of the echo reduction between (a)model 1, (b) model 2, and (c) model 3.

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Fig. 4. Comparison of the acoustic pressure field between (a) model 1 at 10101 Hz , (b) model 2 at 9251 Hz, and (c) model 3 at 8601 Hz.

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Fig. 5. Comparison of the echo reduction between (a) w = 20, (b) w = 25 for model 3.

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Fig. 6. The simulation model of the Helmholtz resonator that combines model 3 and scale unit which is changed the model 3’s entrance width of 5 cm.

GOHHBH_2019_v38n1_67_f0007.png 이미지

Fig. 7. Comparison of the echo reduction between (a) model 3, (b) model 4.

Table 1. Dimensions of the simulation model.

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Table 2. Material properties of the structure (Air) and the medium (Water) used in this study.

GOHHBH_2019_v38n1_67_t0002.png 이미지

Table 3. Boundary conditions used in this study.

GOHHBH_2019_v38n1_67_t0003.png 이미지

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