• Title/Summary/Keyword: 수중 구조물 진동

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Analysis of the Phase Change of a Laser Beam in a Laser Doppler Vibrometer Due To the Sound Field Radiated From Structures Vibrating Underwater (수중에서 진동하는 구조물로부터 방사되는 음에 기인한 레이저 도플러 진동측정기 광선의 위상변화에 대한 분석)

  • Kil, Hyun-Gwon;Jarzynski, Jacek
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.4
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    • pp.178-182
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    • 2008
  • In measurements of the vibration of structures underwater with a laser Doppler vibrometer, the surface vibration is measured by means of detecting the phase change of the laser beam due to the structural vibration. The laser beam passes through the sound field radiated from the vibrating structures underwater. It experiences an additional phase change due to the change in refractive index in the radiated sound field. This phase change due to the sound field may cause the error in surface vibration measurements. In this paper, this phase change due to the radiated sound filed has been analyzed. The numerical simulation has been peformed to evaluate the phase change in sound field radiated from an infinite cylindrical structure vibrating underwater.

Waterborne Noise Prediction of the Reinforced Cylinderical Shell Using the SEA Technique (SEA 기법을 이용한 보강 원통형 셀의 수중방사소음 해석)

  • 배수룡;전재진;이헌곤
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1992.10a
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    • pp.107-112
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    • 1992
  • 선박 내부에 탑재된 추진 기계류에서 발생되는 진동은 마운트 Deck을 통하 여 선체에 전달되어 수중으로 전파된다. 기계류에 의해 발생되는 수중방사소 음을 감소시키기 위해서는 선체로 전달된 진동수준 및 수중방사소음 예측이 우선 중요하다. 수중방사소음 예측 방법으로 FEM과 BEM에 의한 저주파수 대역 예측, 전달함수에 의한 실험적 예측, SEA(Statistical Energy Analysis) 기법을 이용한 고주파수 대역 예측으로 나눌 수 있다. R.H.Lyon 등에 의해 발전된 SEA 기법은 항공기, 선박등 복잡한 구조물의 고주파수 대역 진동해 석에 널리 이용되고 있다. SEA 기법의 선박에 대한 적용은 소형선박의 기계 류에서 발생되는 진동에 의한 선체 진동수준 및 수중방사소음 해석 등에 적 용되고 있다. 본 연구에서는 보강 원통형 셀 모델에 대한 수중방사소음을 SEA 기법을 이용하여 예측하고 실험을 통하여 검증하였다.

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A Case Study on the Vibration Propagation Characteristics by Underwater Rock Cutting Work (수중 쇄암작업에 따른 진동 전파 특성에 관한 시공 사례)

  • Lim, Dae-Kyu;Shin, Young-Cheol;Kim, Young-Min;Lee, Chung-Eon
    • Explosives and Blasting
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    • v.33 no.2
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    • pp.25-39
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    • 2015
  • The common underwater rock removal methods involve underwater blasting and crane's chisel dropping impact method. From an environmental point of view, these methods cause ground vibrations and underwater noise. At the site for this study, a method of dropping heavyweight chisel is selected to remove the underwater bedrock near the ferry rack in the course of improving the cargo handling ability of the loading dock. A prediction formula for the vibration was obtained based on the measurement and evaluation of the vibrations caused by the chisel dropping impacts during the test droppings. The prediction formula was successfully applied to the main construction for securing the stability of the structure.

Modal Characteristics and Vibration Control of Cylindrical Shell Structure: Experimental Results Comparison in the Air and Water (실린더형 쉘 구조물의 모드 특성 및 진동제어: 공기중 및 수중 실험결과 비교)

  • Sohn, Jung-Woo;Kwon, Oh-Cheol;Choi, Seung-Bok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.04a
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    • pp.384-389
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    • 2009
  • In the present paper, dynamic characteristics and vibration control performance of a cylindrical shell structure are experimentally investigated and results are presented in the air and underwater conditions. End-capped cylindrical shell structure is manufactured and Macro-Fiber Composite (MFC) actuators are attached on the inside-surface of the structure. Modal characteristics are studied in the air and under the water conditions and then equation of motion of the structure is derived from the test results. Structural vibration control performances of the proposed structure are evaluated via experiments with optimal control algorithm. Vibration control performances are presented both in the frequency and time domains.

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Modal Characteristics and Vibration Control of Cylindrical Shell Structure : Experimental Results Comparison in the Air and Water (실린더형 셸 구조물의 모드 특성 및 진동제어 : 공기중 및 수중 실험결과 비교)

  • Sohn, Jung-Woo;Kwon, Oh-Cheol;Choi, Seung-Bok
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.9
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    • pp.899-906
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    • 2009
  • In the present paper, dynamic characteristics and vibration control performance of a cylindrical shell structure are experimentally investigated and results are presented in the air and underwater conditions. End-capped cylindrical shell structure is manufactured and macro-fiber composite(MFC) actuators are attached on the inside-surface of the structure. Modal characteristics are studied in the air and under the water conditions and then equation of motion of the structure is derived from the test results. Structural vibration control performances of the proposed structure are evaluated via experiments with optimal control algorithm. Vibration control performances are presented both in the frequency and time domains.

Flow-Chart for Influence Estimation of Underwater Blasting (수중발파의 영향평가를 위한 Flow-Chart)

  • Park, Sun-Joon;Park, Yeon-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.5
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    • pp.47-54
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    • 2008
  • In this study, ground vibration values and damping coefficient produced by underwater blasting were measured and analyzed. Equations of vibration, $V=K(SD)^{-0.536}$, were presented from quantitative experiment results. The K Values are classified with 1.507, 2.005 and 2.939 respectively at 50%, 90% and 95% reliability. Also, hydrospace noise in aquafarm and noise in atmosphere as well as ground vibrations were measured, and maximum values of these results were 86.8dB(A), 147.8dB(A), 0.244cm/s, respectively. Equations of hydrospace noise, $SL=293.2SD^{-0.164}$, was presented from quantitative experiment results. Also, the flow-chart for influence estimation and underwater blast design was presented from these results. The results of the study may be applied for the evaluation of the influence on aquafarm as a basic data before having main underwater blasting at construction sites.

Underwater Structure-Borne Noise Analysis Using Finite Element/Boundary Element Coupled Approach (유한요소/경계요소 연성해석을 통한 수중 구조기인소음 해석)

  • Lee, Doo-Ho;Kim, Hyun-Sil;Kim, Bong-Ki;Lee, Seong-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.7
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    • pp.789-796
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    • 2012
  • Radiated noise analysis from a ship structure is a challenging topic owing to difficulties in the accurate calculation of the fluid-structure interaction as well as owing to a massive degree of freedom of the problem. To reduce the severity of the problem, a new fluid-structure interaction formulation is proposed in this paper. The complex frequency-dependent added mass and damping matrices are calculated using the high-order Burton-Miller boundary integral equation formulation to obtain accurate values over all frequency bands. The calculated fluid-structure interaction effects are added to the structural matrices calculated by commercial finite element software, MSC/NASTRAN. Then, the impedance and underwater radiation noise due to an excitation of structure are calculated. The present formulation is applied to a ship to calculate the underwater radiated noise.