• The Journal of the Acoustical Society of Korea
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• v.41 no.3
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• pp.268-277
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• 2022

In this study, each component of flow noise source of underwater propeller installed to the scale model of the KVLCC2 is investigated and the effect of each noise source on underwater-radiated noise is quantitatively analyzed. The computation domain is set to be the same as the test section of the large cavitation tunnel in the Korea Research Institute of Ship and Ocean Engineering. First, for the high-resolution computation of flow field which is noise source region, the incompressible multiphase Delayed Detached Eddy Simulation is performed. Based on flow simulation results, the Ffowcs Williams and Hawkings integral equation is used to predict underwater-radiated noise and its validity is confirmed through the comparison with the tunnel experiment result. For the quantitative comparison on the contribution of each noise source, the spectral levels of sound pressure and power levels predicted using propeller tip-vortex cavitation, blade surface and rudder surface as the integral region of noise sources are investigated. It is confirmed that the cavitation which is monopole noise source significantly contributed to the underwater-radiated noise than propeller blades and rudder which is dipole noise source, and the rudder have more contribution than propeller blades due to the influence of the propeller wake.

• Journal of KSNVE
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• v.8 no.2
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• pp.232-238
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• 1998

선박 방사소음은 군사적 목적의 수동소나가 탐지대상으로 하는 수중음향 표적이라 할 수 있다. 따라서 수동소나 운용자는 대잠전 수행이전에 다양한 선박들에 대한 방사소음을 측정, 분석하여 개별 선박 고유의 음향 특징을 수집함으로써 실전 상황에서 미지 선박이 탐지되는 경우 이들 자료를 식별의 기초자료로 활용하고자 한다. 또한 새로운 수동소나의 개발자나 스텔스 능력의 선박 설계자 역시 선박방사소음 특징자료를 필요로한다. 본 글은 선박방사소음의 발생기구, 측정시스템 및 측정자료의 분석 평가 기술을 연구분석한 내용이다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.407-408
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• 2014

본 논문은 3차원 수중방사패턴 예측을 위하여 수중구조물의 표면진동장을 이용하여 3 차원 원음장 패턴을 예측한 뒤 수중구조물의 근접음장 계측데이터를 활용하여 산출된 원음장 음향파워를 이용하여 산출된 원음장 패턴의 음압크기를 보정하였고 이를 실험데이터와 비교 분석한 논문이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.599-607
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• 2006

The ship radiated noise appear the various characteristic signals due to the mechanic system in the ship, the propeller and the interaction between ship body and sea water. Generally, it is classified two main components: the speed dependent signal and the speed independent signal. It is required that very complex procedure to classify the signal origin from the ship-radiated noise. This paper presents techniques to automatically detect and classify the tonal signals ken the ship-radiated noise, using the Q factor and the neural network.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.443-446
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• 2004

추진기에 의한 소음은 선형 특성에 의한 반류 분포, 추진기 재질 및 유체 연동 등 다양한 주변 인자들에 의해 발생하여, 민수용 선박의 경우는 과도한 추진기 수중 방사 소음으로 해양 생태계 교란 및 선박 거주구역 내 과대 소음 형성의 주 요인이 된다. 더구나, 군사용 함정의 경우에는 추진기 유기 소음은 수중 방사소음의 형태로 전파되어 함정/무기 자체에 탑재된 음향센서의 기능을 저하시키는 영향을 줄 뿐 아니라, 원거리까지 전파되는 수중소음으로 인해 치명적인 자기 노출이 되어 적 함정에 의한 피탐 거리 증대라는 전술적 취약점을 초래하는 중요한 요소이다. 본 발표는 삼성 공동수조(SCAT)에서 이루어지는 추진기 유기 소음 측정에 대한 기술적 사항과 모형선-추진기 수조 시험을 통해 구해진 추진기 유기음향과 이론 및 경험식을 토대로 계산된 추진기 소음의 정량/정성적 비교를 통해, 추진기 설계 단계에서 소음수준 예측 도구로의 활용 가능성을 제시하였다.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.362-371
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• 2022

As considerable interests in noise emission from the ships have been increased, International Maritime Organization (IMO) standardized the Underwater Radiated Noise (URN) measurement process of commercial ships in deep seas by enacting the related ISO standard ISO 17208-1 and classification societies responded with the enactment or revision of corresponding notations. According to this trend, a new hybrid underwater sound propagation model based on underwater sound propagation theories was developed and its accuracy on analysis was verified through the result comparison with the results of other generally used models. Using the verified model, each URN propagation characteristics adjusted by the correction methods proposed in the ISO standard and class notations were analyzed and compared in two assumed URN measurement cases. The results showed that the effects of transmission loss corrections in the circumstances with less bottom reflections generally similar but they had rather large differences in the model analysis results with bottom-reflection-dominant conditions. It was concluded that the deep consideration of effective bottom-reflection-correction method should be made in future revisions of ISO standard and class notations.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.38-45
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• 2021

In this study, changes in cavitation pattern and noise by air injection were investigated experimentally in a cavitation tunnel. Air injection system that can control the location and the amount of air was manufactured and installed in an elliptic wing that exhibits similar characteristics to those of a propeller blade. Various types of cavitation were simulated on the hydrofoil by adjusting the test conditions in the cavitation tunnel, and the changes in cavitation pattern and noise according to air injection were experimentally analyzed. It was shown that the noise characteristics varied depending on the position and the amount of air injection. This means that in order to apply the air injection technology to the propeller, it is necessary to optimize the air injection location and the amount of injection according to the cavitation characteristics.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.2
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• pp.158-163
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• 2012

Recently, reducing underwater radiated noise (URN) of ships has become an environmental issue to protect marine wildlife. URN of ships can be predicted by various methods considering its generating mechanism and frequency ranges. For URN prediction due to ship structural vibration in low frequency range, the fluid-structure interaction analysis technique based on finite element and boundary element methods (FE/BEM) is regarded as an useful technique. In this paper, URN due to a double bottom-shaped structure vibration has been numerically investigated based on a coupled method of FE/BEM to enhance the prediction accuracy of URN due to the vibration of real ship engine room structure. Acoustic radiation efficiency and URN transfer function in case of vertical harmonic excitation on the top plate of double bottom structure have been evaluated. Using the results, the validity of an existing empirical formula for acoustic radiation efficiency estimation and a simple URN transfer function, which are usually adopted for URN assessment in initial design stage, is discussed.

• Journal of KSNVE
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• v.6 no.6
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• pp.717-726
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• 1996

In this report, the underwater sound radiation from finite cylindrical shell with stiffeners which is the basic configuration of submerged vehicle is studied analytically and experimentally. The shell vibrations are obtained by using the shell theory of Sanders-Koitter. The stiffeners and modeled for I-type and the stiffness matrices are obtained by using beam model. In the analytical stuides, the vibrations of cylindrical shell are expressed by using cosine series expansions to consider the arbitrary end boundary conditions. It is agree to the theoretical and experimental results well.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.311-318
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• 2021

Underwater, signals are transmitted by sound waves. Sound waves are transmitted through a multipath, either directly or through reflection, due to the variety of underwater environmental characteristics. In such diverse and complex underwater environments, tests must be conducted to determine the extent of the hazard from the survivability and pitfalls of submarines by measuring the underwater radiated noise. Usually, the sound source level measurement of underwater radiated noise should be made within the closest point (CPA: Closest Point of Approach) ± a few meters between the measurement sensor and the submarine. In this study, FDOA and TDOA methods were proposed to estimate the underwater source range. A simulation based on the underwater channel model confirmed the performance of the proposed method.