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황하정(Hajung Hwang),우진호(Jinho Woo),나원배(Won-Bae Na),김현주(Hyeon-Ju Kim) 한국해안해양공학회 2015 한국해안해양공학회 논문집 Vol.27 No.2
본 연구에서는 연결재(커플러)로 결합된 라이저의 외부흐름에 따른 3차원 유동-구조 연동해석을 수행하였다. 두 가지 연결재(평면 커플러, 곡면 커플러)를 고려하였으며 ANSYS CFX를 사용하여 수치해석을 수행하였다. 유동해석에서 유동공간은 유입구, 유출구와 대칭 경계조건으로 구성되었으며 연결재의 형상에 따른 항력계수와 유속분포 결과를 비교하였다. 구조해석에서는 라이저의 응답(최대 변위 및 최대 등가응력)을 통해 연결재의 유용성을 확인하였다. This study presents a 3-dimensional flow-structure interaction analysis of subsea risers in water flows. Two structural connectors (flat and circular couplers) were intentionally devised and numerically tested using ANSYS CFX to investigate how these couplers behave under the water flows. In the flow analysis, the water field was constructed with an inlet, outlet, and symmetric boundary conditions. As a result, the responses (drag coefficients and pressure fields) were obtained and the pressure fields were applied for the structural analysis. Finally, the structural responses (displacements and equivalent stresses) of the risers were measured to demonstrate the efficiency of the riser connectors.
황하정(Hajung Hwang),나원배(Won-Bae Na),김현주(Hyeon-ju Kim) 한국해양환경·에너지학회 2013 한국해양환경공학회 학술대회논문집 Vol.2013 No.11
해양에서 생산되는 에너지는 물론 수자원이 육지로 운반되는 과정에서 라이저의 안정성은 중요하다. 해양환경에서 이들 구조물이 받는 외력은 종종 예측하기 어려우며 안정한 해역에서도 수압을 비롯한 다양한 외력을 고려해야한다. 또한 외력으로 인해 발생하는 손상은 라이저에 치명적으로 작용할 수 있으므로 외력에 저항하는 설계가 필요하다. 파이프의 연결부위인 이음부가 외력에 취약하므로 이를 해석대상으로 이음부가 있는 경우와 없는 경우를 비교하였다. 이음부에 에폭시 접착제를 도포하여 모재 전체를 감싸는 형태를 고안하여 이를 3차원으로 모델링하였다. 라이저는 수직으로 거치되며 외관 길이의 변화를 두며 유속변화에 따른 횡하중이 작용하는 라이저의 변위와 응력에 대한 응답해석을 수행하였다. It is known that the stability of subsea risers is significant when the risers transport deep sea water to lands. In marine environment, it is hard to predict or estimate external forces on the risers. Also, the damage occurred by external forces can be severely extended into structural instability; hence, the structural design should be carefully carried out. Especially, the structural members connecting pipes are critically weak against external forces so that in the study we investigated the structural responses of the connecting members in water flows. For the purpose, 3D finite element models were constructed by introducing a connecting method, which adopted adhesive epoxy. Finally, considering various water flows the displacements and stresses were obtained and compared.
이선민(Seonmin Lee),황하정(Hajung Hwang),나원배(Won-Bae Na) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.6
Eco-friendly and sustainable seaweed biomass energy have been under the spotlight as the future of renewable energy. However, seaweed culture is primarily conducted inshore, with the research on offshore culture still an early stage. For massive biomass production, a systematic engineering approach is required to devise offshore seaweed culture facilities rather than the conventional empirical ones. To establish the fundamental behavior of seaweed culture facilities, the dynamic characteristics of a seaweed culture facility were analyzed in the study. For this purpose, numerical analyses of the seaweed culture facility (a frame type) were carried out by using the hydrodynamic simulation program ANSYS-AQWA. For the analysis, environmental loads were considered using the wave spectra and co-linear current, mooring variables were selected as parameters; and time domain analyses were carried out to acquire the time series responses and eventually the dynamic characteristics. Finally, the mooring performance was evaluated. It was found that the motion could be controlled by adjusting the buoyancy and mooring slope.