• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.387-395
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• 2018

In this study, the noise characteristics of the propeller tip vortex cavitation and its inception were analyzed experimentally. Generally, tip vortex cavitation is the first appeared cavity that occurs in a propeller. If propeller tip vortex cavitation is appeared, the level and characteristics of underwater radiated noise changes dramatically compared with the non-cavitating propeller. Therefore, it is very important to analyze the noise characteristics of the propeller cavitation and to detect the cavitation inception in the development of the propulsion system for military vessel and underwater weapon system. The change of noise characteristics due to the inception and growth of the propeller tip vortex cavitation was analyzed. Various imaging-noise measurement and analysis technique were used to determine the inception of propeller cavitation.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.167-170
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• 2004

본 논문에서는 수중익 버블 캐비테이션과 날개 끝 볼텍스 캐비테이션의 거동 및 소음을 Eulerian-Lagrangian 기법을 이용하여 수치적으로 해석하였다. Eulerian-Lagrangian 기법은 캐비테이션 버블이 유동장에 미치는 영향이 거의 없다는 가정하에 유동장과 캐비테이션 거동을 일방으로 연계하여 해석하는 방식이다. 수중익 버블 캐비테이션 해석을 위한 유동장은 비압축성 RAMS 방정식을 해석하여 구하고 날개 끝 볼텍스 캐비테이션 유동장은 일반적 CFD 기법의 큰 수치 소산으로 그 특성이 잘 나타나지 않으므로 Sculley 볼텍스 모델을 이용하여 해석한다. 해석한 유동장 정보를 입력치로 하고 버블의 지배 방정식인 Rayleigh-Plesset 방정식과 Newton의 제2법칙에 근거한 궤적 방정식을 연계하여 캐비테이션의 성장-붕괴와 운동을 예측한다. 계산된 거동 정보를 이용하여 버블 캐비테이션과 날개 끝 볼텍스 캐비테이션의 소음을 예측하였다. 본 연구는 수중 운동체에서 발생하는 캐비테이션의 거동과 소음의 특성을 파악하고 그에 따른 대비책을 마련하는 기본 연구로서 활용할 수 있을 것이다.

• The Journal of the Acoustical Society of Korea
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• v.26 no.5
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• pp.220-226
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• 2007

The two major objectives of acoustical measurements in a cavitation tunnel are measuring the noise levels generated by rotating propellers behind a hull and localizing possible noise sources in order to reduce noise levels. Propeller noise measurement experiments were performed in MOERI cavitation tunnel at December, 2006. In order to put the propeller into cavitating conditions, a wake-generating dummy body was devised. In addition, ten hydrophones are put inside a wing-shaped casing in order to minimize the unexpected flow induced self noise around hydrophone itself. After measuring both of the noises of the rotating propeller behind the dummy body and signals generated by a virtual source, respectively the data were matched field processed using the frequency incoherent Bartlett processor to localize noises on the propeller plane. In this paper, we presented the measured noise analysis and the localization results.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.2
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• pp.14-21
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• 2000

The cavitation noise of 2-D hydrofoils is measured a cavitation tunnel. A new experimental method was developed for the noise measurement of 2-D hydrofoil. Three hydrofoils with the span of 600mm are designed and manufactured to investigate cavitation behavior and noise characteristics. The experimental results show the noise characteristics of various cavitation patterns and the noise performance of the three foils very well. This suggests that low-noise propeller blade section can be developed using the present experimental method.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.23-30
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• 2001

The cavitation noise of high-speed propellers was experimentally studied using new measurement device in KRISO cavitation tunnel. A series of cavitation noise tests were carried out for 6 propellers with various sections, loading distributions, and a different area ratio. From the experimental results, the noise characteristics for various cavitation patterns and the noise performance for a series of propellers were analyzed. These can be used for full-scale prediction study of the noise and optimum design of high-speed propellers.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.328-333
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• 2019

In this paper, to investigate the cavitation erosion phenomenon on the ship propeller, the correlation between the propeller noise and the cavitation intensity was analyzed. Cavitation erosion is closely related to cavitation collapsing intensity, which can be defined as the frequency and intensity of cavitation collapse. The pressure wave generated by cavitation collapse appears as a continuous acoustic pulse and this result is analyzed with the cavitation behavior to determine the relationship of the propeller noise to cavitation collapse intensity. This technique is applied to the propeller erosion test using the inclined shaft propeller model.

• 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.31 no.1
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• pp.84-93
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• 1994

The purpose of present study is to investigate the surface roughness on tip-vortex cavitation and its induced noise, emanating from an elliptic wing of NACA 0012 section. Roughness elements of $200{\mu}m$ are applied to the 10% portion of wing tip, and then, the wing tip as well as the leading edge. It is shown from cavitation observation that the cavitation inception is first visible at about half chord downstream of wing tip for most experimental conditions, and developed into the tip-vortex cavitation and finally the fully developed cavitation as cavitation number is decreased. Acoustic noise generated by a tip-vortex cavitation has its frequency range of 3 kHz to 50 kHz, while the fully-developed cavitation at lower cavitation number induces a broad band spectrum. It is also shown that, when the roughness elements are applied to the wing tip and the leading edge, the cavitation characteristics and its induced noise are improved. Moreover, it is appeared that the condition at which the rough surface is at pressure side gives a better result. although its lift-drag ratio is reduced.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.2
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• pp.22-29
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• 2000

The cavitation noised of high-speed propellers was experimentally studied in KRISO cavitation tunnel. In this paper, a series of cavitation noise tests were carried out for five propellers with various sections and loading distributions. From the experimental results, the noise characteristics of various cavitation pattern and the noise performance of the propellers were analyzed. There can be used for optimum design for high-speed propellers.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1170-1174
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• 2014

If cavitation occurs in propeller, it generates vibration and noise accordingly which results in low efficiency of propeller. It's important to increase cavitation inception speed(CIS) since the noise of cavitation increases significantly from the beginning of cavitation. This paper describes the result of actual observation and measurement onboard ship with controllable pitch propeller(CPP), so as to verify the first occurrence phenomenon of cavitation. The research suggests new type of controllable pitch propeller with improved CIS at the bolt as it started with bolt cavitation as result of observation. It's not found bolt cavitation on the CPP proposed in this paper, furthermore its CIS is increased approximately by 4.5 knots than the existing CPP. The result of the research can be used for development of low-noise CPP and improving performance of CIS.