• 수산해양기술연구
• /
• 제44권1호
• /
• pp.46-56
• /
• 2008

A numerical model analysis was performed to analyze the motion and mooring tension response of submersible fish cage systems in irregular waves and currents. Two systems were examined: a submersible cage mooring with a single, high tension mooring and the same system, but with an additional three point mooring. Using a Morison equation type model, simulations of the systems were conducted with the cage at the surface and submerged. Irregular waves(JONSWAP spectrum) with and without a co-linear current with a magnitude of 0.5m/s were simulated into the model as input parameters. Surge, heave and pitch dynamic calculations were made, along with tension responses in the mooring lines. Results were analyzed in both the time and frequency domains and linear transfer functions were calculated.

• 한국해양공학회지
• /
• 제23권1호
• /
• pp.89-95
• /
• 2009

The purpose of the present study was to evaluate the safety under extreme environmental conditions and the dynamic safety under service environment conditions, of oceanographic buoy mooring systems consisting of a variety of materials, including chain, wire rope, nylon rope, and polypropylene rope. For the static safety assessment of a mooring system, after the calculation of external forces and the division of a mooring system into finite elements, the numerical integral was conducted to yield the elemental static tension until satisfying the geometrical convergence condition. To evaluate the dynamic safety, various processes were considered, including data collection about the anticipated areas for mooring, a determination of the parameters for the interpretation, the interpretation of the dynamic characteristics based on an analytic equation that takes into account the heave motion effect of a buoy hull and a mooring system, and a fatigue analysis of the linear cumulative damage. Based on the analysis results, a supplementary proposal for a wire rope that has a fracture in an actual mooring area was established.

• 한국해양공학회지
• /
• 제31권4호
• /
• pp.274-280
• /
• 2017

Generally, global performance analysis in offshore platforms is performed using potential-based numerical tools, which neglect hydrodynamic viscous effects. In comparison with the potential theory, computational fluid dynamics (CFD) methods can take into account the viscous effects by solving the Navier-Stokes equation using the finite-volume method. The open-source field operation and manipulation (OpenFOAM) C++ libraries are employed for a finite volume method (FVM) numerical analysis. In this study, in order to apply CFD to the global performance analysis of a hull-mooring coupled system, we developed a numerical wave basin to analyze the global performance problem of a floating body with a catenary mooring system under regular wave conditions. The mooring system was modeled using a catenary equation and solved in a quasi-static condition, which excluded the dynamics of the mooring lines such as the inertia and drag effects. To demonstrate the capability of the numerical basin, the global performance of a barge with four mooring lines was simulated under regular wave conditions. The simulation results were compared to the analysis results from a commercial mooring analysis program, Orcaflex. The comparison included the motion of the barge, catenary shape, and tension in the mooring lines. The study found good agreement between the results from the developed CFD-based numerical calculation and commercial software.

• International Journal of Ocean System Engineering
• /
• 제2권2호
• /
• pp.97-105
• /
• 2012

A all floating structures operating within a limited area require, stationkeeping to maintain the motions of the floating structure within permissible limits. In this study, methods for selecting and optimizing the mooring system Caisson for floating wind turbines in shallow water are investigated. The design of the mooring system is checked against the governing rules and standards. Adequately verifying the design of floating structures requires both numerical simulations and model testing, the combination of which is referred to as the hybrid method of design verification. The challenge in directly scaling moorings for model tests is the depth and spatial limitations of wave basins. It is therefore important to design and build equivalent mooring systems to ensure accurate static properties (global restoring forces and global stiffness).

• 한국항해항만학회지
• /
• 제34권5호
• /
• pp.311-317
• /
• 2010

하역장치가 장착된 모바일하버 선박은 새로운 해상운송시스템 개념으로, 특정 정박지에서 대형 컨테이너 선박에 계류하여 해상상태 3 이하 조건에서 신속하면서 효율적인 컨테이너 하역작업을 수행하는 것이다. 모바일하버와 관련한 주요 연구로는 고속하역시스템, 부유체 구조 설계, 안벽하역시스템 해석 및 작업크레인 설계 등의 원천기술 개발을 중심으로 수행되었다. 본 연구는 모바일하버 선박의 하역작업 중 동적안정성 확보를 위한 계류안정화시스템을 개발하고자 하는 것으로, 국내외 계류장치에 대한 현황 분석을 기초로 현재 선박에 탑재되어 있는 의장장치인 윈치시스템에 계류안정화 기능을 추가시킨 포지셔닝윈치를 개발하여 모선과의 상대운동을 최소화하는 방안에 대한 개념설계를 제안한다.

• 한국해양공학회지
• /
• 제33권2호
• /
• pp.99-105
• /
• 2019

Unlike typical a dynamic positioning (DP) system, a DP-assisted mooring system must determine a set point (SP) that can ensure a mooring tension safety range to prevent an excessive increase in mooring tension. In this paper, a new algorithm for determining the SP is suggested in order to reduce the tension on all the mooring lines. To determine the SP, a working area around the vessel is represented by a rectangular grid. Thus, the size of the grid area is limited considering the offset of a vessel with a mooring system. At each grid's nodes, the resultant tension from all the mooring lines is estimated using the time history of the tension and vessel's position. The results of static analyses for each grid position are used to estimate the global tension. Consequently, the SP is automatically selected as a position satisfying criterion for minimizing the total tension. In order to validate the suggested algorithm, a motion simulation with the control system in the time domain and a discussion of the results are presented.

• 해양환경안전학회지
• /
• 제28권5호
• /
• pp.819-826
• /
• 2022

스마트 항만시스템을 구축하기 위해서는 무엇보다 선박을 자동으로 계류시킬 수 있는 시스템이 요구된다. 항만의 자동계류시스템의 허용 계류력을 산정하기 위해서는 선박의 특성을 고려하고, 해양환경적 외란으로 부터 발생된 외력을 정확히 계산해야 한다. 이러한 환경적 외란의 크기를 정확히 추정하는 것은 자동계류장치 설계를 위해서 매우 중요한 요소이다. 본 연구에서는 항만 및 어항 설계기준에 따라 한바다호에 대한 계류력을 추정하였다. 그 결과 한바다호에 작용하는 대부분의 외력은 바람으로부터 기인되는 것을 확인하였다. 가장 극한 해양조건(B.F 6)에서 한바다호에 작용하는 종방향 힘은 18kN, 횡방향 힘은 248kN으로 나타났다.

• 수산해양기술연구
• /
• 제35권2호
• /
• pp.201-208
• /
• 1999

To develop a new fish cage which is required for offshore or moving cage culturing system has been gradually increased against being closely dense of fish cage in shallow water. Though submersible fish cage culturing system is essential technology for converting from shallow water into the offshore, it was pointed out the serious problem about stability of which are sinking and floating state. This study is presented conceptual design of submersible fish cage centered with a mooring steel pile to acquire stability and faculty. Design of mooring steel pile for submersible fish cage culturing system needs to carry out optimal design of mooring steel pile for which much efforts are required. Formulation and optimal design process of submersible fish cage are organized into using Sequential Quadratic Programming method of numerical optimization. For submersible fish cage system centered with a mooring steel pile, process of the optimal design is proposed and the optimal solutions are obtained.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권3호
• /
• pp.559-579
• /
• 2015

An experimental study of the effect of mooring systems on the dynamics of a SPAR buoy-type floating offshore wind turbine is presented. The effects of the Center of Gravity (COG), mooring line spring constant, and fairlead location on the turbine's motion in response to regular waves are investigated. Experimental results show that for a typical mooring system of a SPAR buoy-type Floating Offshore Wind Turbine (FOWT), the effect of mooring systems on the dynamics of the turbine can be considered negligible. However, the pitch decreases notably as the COG increases. The COG and spring constant of the mooring line have a negligible effect on the fairlead displacement. Numerical simulation and sensitivity analysis show that the wind turbine motion and its sensitivity to changes in the mooring system and COG are very large near resonant frequencies. The test results can be used to validate numerical simulation tools for FOWTs.

• Journal of Advanced Research in Ocean Engineering
• /
• 제4권1호
• /
• pp.25-34
• /
• 2018

In this study, the behavior of the coupled mooring system and floating body is analyzed. The related works are introduced for the mooring analysis of the floating body. Equations motion are introduced for calculating mooring force connected with the floating body. For formulating the equations of motion, the concept of the constrained force is applied for compact expression of it. The input and output data of the module for calculating mooring force is defined. The static analysis and quasi-static analysis are performed. For the analysis, equilibrium equation for elastic catenary mooring line is used by employing finite element method, and the C# solver is developed in this research. The analysis results are validated by comparing with other research results.