• 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.

• Explosives and Blasting
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• v.30 no.2
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• pp.66-76
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• 2012

Blasting technology aims to maximize digging efficiency as well as minimize vibration and noise. So, it is key point of blasting technology to raise blasting effect as much as possible and reduce vibration and noise and the design of PLHBM that is the tunnel blasting method having such merit was studied in this paper. PLHBM has the excellent blasting efficiency as it drills the empty hole with high caliber of 250~1,000mm at centre cut, contributes to blasting vibration reduction effect much and can be usefully applied to tunnel blasting sites. So it is judged that it enables the development of tunnel blasting method to be advanced one more step by studying and suggesting the design method of PLHBM.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.930-938
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• 2018

Underwater noise radiated from submarines is directly related to the probability of being detected by the sonar of an enemy vessel. Therefore, minimizing the noise of a submarine is essential for improving survival outcomes. For modern submarines, as the speed and size of a submarine increase and noise reduction technology is developed, interest in flow noise around the hull has been increasing. In this study, a noise analysis technique was developed to predict flow noise generated around a submarine shape considering the free surface effect. When a submarine is operated near a free surface, turbulence-induced noise due to the turbulence of the flow and bubble noise from breaking waves arise. First, to analyze the flow around a submarine, VOF-based incompressible two-phase flow analysis was performed to derive flow field data and the shape of the free surface around the submarine. Turbulence-induced noise was analyzed by applying permeable FW-H, which is an acoustic analogy technique. Bubble noise was derived through a noise model for breaking waves based on the turbulent kinetic energy distribution results obtained from the CFD results. The analysis method developed was verified by comparison with experimental results for a submarine model measured in a Large Cavitation Tunnel (LCT).

• 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.7 no.2
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• pp.189-198
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• 1997

현재 행해지고 있는 환경 기술자에 의한 공해성 환경영향평가와 택지조성사업, 터널공사, 각종 도로공사, 건물 해체 작업시 이루어지는 발파 기술자에 의한 발파 영향평가 및 토목. 건축 기술자들에 의해 시공현장에서 주로 행해지는 기타 건설 소음. 진동 영향평가는 진단 개념에서 볼 때, 측정목적과 측정대상에 따른 각종 기준적용과 측정방법 및 분석절차 상에서 몇가지 문제점을 안고 있으며 실제 현장 계측시에도 측정위치 선정, 센서부착 방법, 측정 횟수 및 측정 모드 선정 등에서 상당한 오류를 범하는 것을 종종 볼 수 있다. 따라서 본 연구에서는 각종 소음. 진동 영향평가의 현실태 및 피해 대상물에 대한 진단시 우려되는 기준 적용, 측정 및 분석상의 문제점들을 조사하고 개선방안을 살펴봄으로써 소음. 진동 피해진단 기술을 정립하고 향후과제에 대해 논의하고자 한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.341-344
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• 2005

High-speed trains with maximum speed of 300km/h, named KTX, have started revenue services since April 2004. Because of the geographical features of Korea a large portion of the 'Kyung-Bu' line is comprised of tunnels, which may cause excessive noise in a vehicle. The KTX interior noise follows in tunnel structure and the place where the quality appears different, the quality against hereupon from the commerce vehicle from the research which it sees it executes and comparison to analyze.

• Journal of the Korean Society for Advanced Composite Structures
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• v.7 no.1
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• pp.19-24
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• 2016

Most of the soundproof tunnels generate significant discharge noise through their inlets and outlets so that the length of the tunnel has been extended frequently than required to minimize the effect on such discharge noise. Thus, in this paper, we investigate reduction capability of discharge noise from the sound proof tunnel installed with lateral sound-absorbing panels on the partitioned truss members in the longitudinal direction of the tunnel. In conclusion, noise field analysis results shows that the sound proof tunnels with lateral sound-absorbing panels have an effect on discharge noise abatement and thereby tunnel's length reduction.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.122-127
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• 2008

The source of wayside noise for the train are the aerodynamic noise, wheel/rail noise, and power unit noise. The major source of railway noise is the wheel/rail noise caused by the interaction between the wheels and rails. The Structure borne noise is mainly a low frequency problem. The train noise and vibration nearby the elevated railway make one specific issue. The microphone array method is used to search sound radiation characteristics of elevated structure to predict the noise propagation from an elevated railway. In this paper, the train noise and structure borne noise by train are measured. From the results, we investigated the effect on the sound absorption tunnel for elevated railway.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.361-362
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• 2014

본 연구의 목적은 벤토나이트 완충재를 처분공에 설치하였을 때 벤토나이트와 암반의 상호작용을 중심으로 이의 포화과정을 제대로 모사할 수 있는 지와, 현장암반의 절리가 수치해석 결과에 어떠한 영향을 미치는가를 파악하는 것이다. 유한차분 해석코드인 TOUGH2 코드를 이용하여 벤토나이트의 수리거동을 분석하였다. 해석결과 암반의 절리가 존재할 경우 완충재의 포화도는 상대적으로 매우 빠르게 진행되었으며, 벤토나이트의 높은 모세관 압력으로 인해 시간경과에 따라 주변암반의 포화도가 점진적으로 감소됨을 확인하였다.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.454-459
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• 2013

Pressure waves are generated and propagate in a tunnel when train enters tunnel high speed. A compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as an expansion wave. An expansion wave due to the entry of the train tail propagates along the tunnel and is reflected at tunnel exit as a compression wave. These pressure waves are repeatedly propagated and reflected at the tunnel entrance and exit. Severe pressure changes causes ear-discomfort for passengers in the cabin and micro pressure waves around the tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnels qualitatively and quantitatively, because pressure change rate is considered as one of the major design parameters for optimal tunnel cross sectional area and repeated fatigue force on car body. In this study, we developed a characteristics method based on a fixed mesh system and boundary conditions for crossing trains and analyzed this system using an X-t diagram. The results of the simulation show that offsetting of pressure waves occurs for special entry conditions of a crossing train.