• 한국전산구조공학회논문집
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• 제31권5호
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• pp.215-226
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• 2018

본 논문에서는 수중폭발(UE: underwater explosion)에 의한 해중터널(SFT: submerged floating tunnel)의 동적거동을 양해법(explicit)를 이용하는 LS-DYNA에 의한 유한요소해석을 통하여 분석하였다. SFT의 유한요소모델은 원형단면의 강재 라이너에 콘크리트가 채워진 복합재 원형단면으로 고려되었다. 해중터널 시스템의 중앙부 100m 구간은 탄소성재료를 고려한 솔리드(solid)요소로 상세하게 모델링하였으며, 양측 방향으로 각각 1km 구간에 대해서는 탄성재료를 고려하여 빔(beam) 요소로 이상화하여 모델링하였다. 사선계류시스템은 케이블(cable)요소를 적용하였으며, 수중폭발에 의한 동적거동시 수리동적질량의 영향을 고려하기 위하여 원형단면에 대한 추가질량을 고려하였다. 또한 부력과 같은 상시하중을 초기조건으로 고려하기 위하여 동적완화해석(dynamic relaxation analysis)를 수행하였다. UE는 부력비(B/W)와 폭발지점으로부터 거리의 변화에 대해서 고려하였으며, 폭발의 규모는 천안함 합동조사보고서(2010)를 참조하여 TNT 360kg로 결정하였다. 수중폭발 해석결과, 폭발지점으로부터 SFT까지 거리는 관입량, 충격압력의 크기와 반비례 관계에 있고, 부력비(B/W)가 커질수록 계류장력도 커짐을 확인하였다. 그러나 사선계류라인의 계류각 변화는 SFT의 수평거동, 관입량, 계류력, 충격압력과의 연관성을 찾을 수가 없었다.

• 한국환경과학회지
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• 제23권12호
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• pp.1977-1985
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• 2014

Many countries around the world are amplifying interest and studies on irrigation, flood control and environment with concern on serious water problems. Especially for irrigation in water supply vulnerable areas such as coastal areas - islands, business on underwater resource security facilities are promoted to secure stable water resources due to development of society and increase of life quality. Also, various policies such as reuse of leaking underwater, utilization of underwater at waterfront, and artificial recharge, etc are planned and designed. In order to develop small sized underwater resource secure technology, verification of seawater-freshwater interface is executed and how the balance between these will develop is a great interest of coastal areas - islands. In this study, seawater-freshwater interface behavior analysis experiment was conducted while reflecting properties of coastal areas - islands and executed hydraulic similitude of saltwater intrusion form control technology on abstraction.

• 한국시뮬레이션학회논문지
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• 제21권1호
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• pp.35-43
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• 2012

본 연구에서는 수중에서 사출되는 양성부력체와 음성부력체의 수중거동을 사출시험 및 시뮬레이션을 통하여 비교하였다. 다양한 형상을 갖는 음성부력체의 동유체력 계수는 전산유체역학(CFD: Computatioanl Fluid Dynamics) 기법을 이용하여 계산하였으며, CFD에 의해 계산될 수 없는 계수는 기본형과 같은 값을 적용하였다. 종동요각의 시험 값은 시뮬레이션 값보다 훨씬 크게 나타났는데, 이는 추종공기 효과로 추정하였으며, 이 현상을 반영하여 외력 모델링을 수정함으로써 더욱 정확한 시뮬레이션이 가능하였다. 양성부력체와 음성부력체의 수중거동은 같은 사출 조건에서 다소 차이를 보이지만, 운용의 관점에서는 별다른 문제가 없는 것으로 판단하였다.

• 한국군사과학기술학회지
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• 제12권5호
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• pp.590-600
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• 2009

In the simulation of underwater vehicles such as a submarine or a torpedo, various type of simulations like an engineering level simulation for predicting the performance precisely and an engagement level simulation for examining the effectiveness of a certain tactic is required. For this reason, a tactics manager which can change the behavior of a simulation model according to external tactics is needed. In this study the tactics manager supporting a script language and engine which can represent various tactics and can help users define external input tactics for the tactic manager easily is suggested. Python and Lua which are representative among script languages have been compared and analyzed from the viewpoint of a tactic manage, and the tactic manger using the script engines of those script languages was implemented. To demonstrate the effectiveness of the tactic manager, a target motion analysis simulation of the warfare between a submarine and a surface ship.

• 수산해양기술연구
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• 제55권2호
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• pp.129-137
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• 2019

This study was conducted to investigate the effects of underwater noise caused by pile driving during marine construction on fish. In this study, the three gray rockfish were released about 1 km away from the construction site of wind power generation on July 18, 2018 and traced using two acoustic telemetry techniques. The behavior of the fish was analyzed by calculating the moving distance, swimming speed and direction of the gray rockfish. In the results of the acoustic tracking using the ship, the rockfish moved about 2.11 km for about two hours at a speed of $0.28{\pm}0.14m/s$ (0.94 TL/s). The bottom depth of the trajectory of the rockfish was $1.0{\pm}0.6m$ on average. There was a significant directionality in swimming direction of the gray rockfish, and there was no significant correlation between the swimming direction and tidal current direction. Moving distance during 5 minutes (5MD) during pile driving and finishing operations between rock surface and bedrock were 0.94-0.96 times (76.0-77.0 m) and 1.81-2.73 times (146.0-219.5 m), respectively, compared with no pile driving. This study is expected to be used as a basic data of fish behavior research on underwater noise.

• Smart Structures and Systems
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• 제15권2호
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• pp.299-314
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• 2015

Submersed rock-berm structures are frequently used for protection of underwater lifelines such as pipelines and power cables. During the service life, the rock-berm structure can experience several accidental loads such as anchor collision. The consequences can be severe with a certain level of frequency; hence, the structural responses should be carefully understood for implementing a proper structural health monitoring method. However, no study has been made to quantify the structural responses because it is hard to deal with the individual behavior of each rock. Therefore, this study presents a collision analysis of the submersed rock-berm structure using a finite element software package by facilitating the smoothed-particle hydrodynamics (SPH) method. The analysis results were compared with those obtained from the Lagrange method. Moreover, two types of anchors (stock anchor and stockless anchor), three collision points and two different drop velocities (terminal velocity of each anchor and 5 m/s) were selected to investigate the changes in the responses. Finally, the effect of these parameters (analysis method, anchor type, collision point and drop velocity) on the analysis results was studied. Accordingly, the effectiveness of the SPH method is verified, a safe rock-berm height (over 1 m) is proposed, and a gauge point (0.5 m above the seabed) is suggested for a structural health monitoring implementation.

• 대한조선학회논문집
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• 제41권2호
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• pp.33-46
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• 2004

The cavitating noise of underwater propeller is considered numerically in this study. The main purpose of this research is to analyze these noise sources from marine propeller. The approach for investigation is a potential based panel method coupled with acoustic analogy. To predict propeller sheet cavitation noise, the blade surface cavity is considered as a single valued pulsating volume of vapor attached to the blade surface. The time dependent cavity volume data are used for noise prediction. Furthermore, we analyze hydrofoil cavitation bubble behavior and noise using Eulerian/Lagrangian approach. Through this study, we can analyze dominant noise source of marine propeller and provide a basis for proper noise control strategies.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권1호
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• pp.9-19
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• 2012

A set of equations of motion is derived for vibratory motions of an underwater cable connected to a moving vehicle at one end and with drogues at the other end. From the static analysis, cable configurations are obtained for different vehicle speeds and towing pretensions are determined by fluid resistance of drogues. Also the dynamic analysis is required to predict its vibratory motion. Nonlinear fluid drag forces greatly influence the dynamic tension. In this study, a numerical analysis program was developed to find out the characteristic of cable behaviour. The motion is described in terms of space and time coordinates based on Chebyshev polynomial expansions. For the spatial integration the collocation method is employed and the Newmark method is applied for the time integration. Dynamic tensions, displacements, velocities, accelerations were predicted in the time domain while natural frequencies and transfer functions were obtained in the frequency domain.

• 한국전산구조공학회논문집
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• 제27권5호
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• pp.369-377
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• 2014

본 논문에서는 해중터널와 수중운항체의 충돌거동을 파악하기 위하여 두 구조체를 모델링하고 해석을 수행하였다. 충돌이 일어나는 해중터널은 원통형으로 단면을 가정하고 콘크리트와 라이닝강판을 가진 구조로 가정하였다. 충돌부위를 제외한 인접부분은 탄성거동을 하는 보요소로 모델링하고 계류라인은 장력을 받는 케이블로 모델링하였다. 수중운항체는 1800톤급 잠수함을 가정하였으며 수리동역학적 부가질량을 고려하여 충돌질량을 산정하였다. 해중터널에 작용하는 부력은 동적완화방법을 사용하여 초기조건에 포함시켰다. 부력비의 변화와 충돌속도의 변화를 고려하여 충돌해석을 수행한 결과, 충돌에너지의 소산은 주로 해중터널에서 발생하고 수중운항체에 의한 에너지 소산은 미미한 것으로 나타났다. 또한 계류라인의 장력과 부력비의 변화에 따라 해중터널의 충돌거동은 큰 영향을 받았다. 특히 충돌력은 기존의 설계기준의 선박충돌력과는 상이한 경향을 보이는 것으로 나타났다.

• 콘크리트학회논문집
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• 제12권5호
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• pp.13-23
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• 2000

In this study, an flexural test on half-scale spliced PSC-I girder was conducted to verify the efficiency of the long span spliced girder as suggested by the Korean Highway Design Specification. The experimental results showed that the specimens developed a complex failure mode due to flexural-compression and torsional stress. The cracking moment of each girder was higher the experiment than was calulated by the ACI and the ultimate strength were the almost same. To estimate the safety and the structural efficiency of the spliced girder, the proposed Yielding Resistance Index(YRI) and ductility index by American Concrete Institutes were used based on the energy concept. The proposed YRI defined the ratio of crack resisting energy and the total energy calculated from load-displacement relationship. Based on the analysis of YRI and ductility index, the flexural behavior of the spliced girder was found to be efficient. Through the experimental results, the structural behavior of proposed spliced PSC I-type girder for long span bridge was found to be more efficient than the exsisting PSC I-type girders.