탄성 변형을 하는 쐐기의 수면 입수 수치 모사

신상묵,김인철,김용직 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5

유체력에 의해 동적 탄성 변형을 하는 쐐기의 수면 입수에 대한 유탄성 해석이 수행되었다. 임의의 밀도 분포를 갖는 비압축성 유체들에 대한 flux-difference splitting 기법을 적용자유 표면 유동이 해석되었으며 동적 탄성 변형을 하는 물체 경계 조건은 hybrid Cartesian/immersed boundary 법을 이용하여 처리되었다. 개발된 코드의 움직이는 물체와 지유 표면 유동의 상호작용에 대한 검증을 위하여 자유 낙하 하는 강체 쐐기의 수면 입수에 대한 수치 모사를 수행하고 시간에 따른 쐐기의 속도 변화 및 쐐기에 작용하는 유체력에 대한 실험 결과 및 다른 계산 결과들과 본 계산 결과를 비교하였다. 유체력에 의한 쐐기의 탄성 변형은 시간에 따른 압력 분포를 하중으로 하는 동적 보 방정식에 의해 모델링되었으며 매 순간 형상 및 변형 속도가 고려된 비정상 자유 표면 유동이 해석되었다. 탄성 변형을 하는 쐐기의 경우, 일정한 속도로 입수하는 경우에 대한 압력장의 시간 변화를 해석하고 동일한 운동을 하는 강체 쐐기 주위 압력장의 시간 변화와 비교하여 구조물의 특성에 따른 탄성 변형이 유체력에 미치는 영향을 관찰하였다.

탄성 변형을 하는 쐐기의 수면 입수 수치 모사

신상묵,김인철,김용직 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5

유체력에 의해 동적 탄성 변형을 하는 쐐기의 수면 입수에 대한 유탄성 해석이 수행되었다. 임의의 밀도 분포를 갖는 비압축성 유체들에 대한 flux-difference splitting 기법을 적용하여 자유 표면 유동이 해석되었으며 동적 탄성 변형을 하는 물체 경계 조건은 hybrid Cartesian/immersed boundary 법을 이용하여 처리되었다. 개발된 코드의 움직이는 물체와 자유 표면 유동의 상호작용에 대한 검증을 위하여 자유 낙하 하는 강체 쐐기의 수면 입수에 대한 수치 모사를 수행하고 시간에 따른 쐐기의 속도 변화 및 쐐기에 작용하는 유체력에 대한 실험 결과 및 다른 계산 결과들과 본 계산 결과를 비교하였다. 유체력에 의한 쐐기의 탄성 변형은 시간에 따른 압력 분포를 하중으로 하는 동적 보 방정식에 의해 모델링되었으며 매 순간 형상 및 변형 속도가 고려된 비정상 자유표면 유동이 해석되었다. 탄성 변형을 하는 쐐기의 경우, 일정한 속도로 입수하는 경우에 대한 압력장의 시간 변화를 해석하고 동일한 운동을 하는 강체 쐐기 주위 압력장의 시간 변화와 비교하여 구조물의 특성에 따른 탄성 변형이 유체력에 미치는 영향을 관찰하였다.

HCIB법을 이용한 변형하는 평판 주위의 3차원 유동해석

신상묵 한국전산유체공학회 2007 한국전산유체공학회지 Vol.12 No.1

A code is developed using the hybrid Cartesian/immersed boundary method and it is applied to simulate flows around a three-dimensional deforming body. A new criterion is suggested to distribute the immersed boundary nodes based on edges crossing a body boundary. Velocities are reconstructed at the immersed boundary nodes using the interpolation along a local normal line to the boundary. Reconstruction of the pressure at the immersed boundary node is avoided using the hybrid staggered/non-staggered grid method. The developed code is validated through comparisons with other experimental and numerical results for the velocity profiles around a circular cylinder under the forced in-line oscillation and the pressure coefficient distribution on a sphere. The code is applied to simulate the flow fields around a plate whose tail is periodically flapping under a translation. The effects of the velocity and acceleration due to the deformation on the periodic shedding of pairs of tip vortices are investigated.

Numerical simulation of fluid-structure interaction of a moving flexible foil

신상묵,김형태 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.12

The hybrid Cartesian/immersed boundary method is applied to fluid-structure interaction of a moving flexible foil. A new algorithm is suggested to classify immersed boundary nodes based on edges crossing a boundary. Velocity vectors are reconstructed at the immersed boundary nodes by using the interpolation along a local normal line to the boundary. For eliminating pressure reconstruction, the hybrid staggered/non-staggered grid method is adapted. The deformation of an elastic body is modeled based on dynamic thin-plate theory. To validate the developed code first, free rotation of a foil in a channel flow is simulated and the computed angular motion is compared with other computational results. The code is then applied to the fluid-structure interaction of a moving flexible foil which undergoes large deformation due to the fluid loading caused by horizontal sinusoidal motion. It has been shown that the moving flexible foil can generate much larger vertical force than the corresponding rigid foil and the vertical force can be attributed to the downward fluid jet due to the alternating tail deflection.

고립내면파의 경사면에 의한 파형 전환 수치모사

신상묵,김인철,김용직 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6

A developed code is applied to simulate the waveform inversion of an interfacial solitary wave due to a submerged trapezoidal obstacle. The interface between two incompressible fluids is regarded as a moving contact discontinuity. An approximated Riemann solver is used to estimate the inviscid flux and the discontinuity across the interface is handled without any artificial smoothing. The time evolution of the interface is captured on the basis of a computed density field, but the computational procedure does not require any information about the instantaneous interface. The hybrid Cartesian/immersed boundary method is used to treat the boundary condition. The immersed boundary nodes are distributed on the basis of the edges crossing the boundary. The dependent variables at the immersed boundary nodes are reconstructed by the interpolation along a local normal line to the boundary. The internal solitary waves are generated by the collapse mechanism, where different interfacial levels on both sides of a vertical sluice gate are given as the initial conditions. Effects of the difference in the interfacial levels and the width of the fluids confined in the sluice gate are investigated. The computed time histories of the internal waves are compared with other computational results and good agreements are achieved. The depression-type internal solitary wave propagates and interacts with a submerged trapezoidal obstacle. The simulation suggests that the incoming depression-type internal solitary wave undergoes the waveform inversion into elevation-type internal waves. The time histories of wave elevations at two places are compared with the experimental results and it is found that the computed waveform inversion is in accordance with the experimental results.

동압 계수의 불연속성을 이용한 내면파의 수치해석

신상묵(Sangmook Shin),김동훈(Dong Hun Kim) 대한조선학회 2004 大韓造船學會 論文集 Vol.41 No.4

상대운동을 하는 방제판 주위 물-기름-공기 유동 모사

신상묵(Sangmook Shin) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.3

The FDS-HCIB method is expanded to simulate water-oil-air flows around oil booms under relative motion, which is intended to increase the thickness of contained oil. The FDS scheme captures discontinuity in the density field and abrupt change of the tangential velocity across an interface without smearing. The HCIB method handles relative motions of thin oil booms with ease. To validate the developed FDS-HCIB code for water-oil-air flow around a moving body, the computed results are compared with the reported experimental results on the shape, length, and thickness of the oil slicks under towing. It is observed that the increase in pressure field between two barriers lifts the oil slick and the interfacial wave propagates and reflects as one barrier gets closer to the other barrier.

비압축성 자유표면 유동에서 갇힌 기체의 등엔트로피 및 등온과정에 따른 공기 완충 효과 변화

신상묵(Sangmook Shin) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3

A developed code is applied to simulate the air cushion effects caused by isentropic and isothermal processes of entrapped air in incompressible free surface flows. The code uses a pressure-based method for the unified conservation laws of incompressible and compressible fluids. To calculate a pressure field, including compressible entrapped gas region, a pressure Poisson equation is solved for the whole domain. The effects of gas compressibility are reflected in the source terms of the pressure Poisson equation. The oscillations of water column in a closed tube are simulated, which are caused by compression and expansion of air on both sides of the water column. A good agreement is achieved for comparison of computed time history of pressure at the end of the closed tube with other reported result. In the isentropic process, the period of the oscillation becomes shorter and the amplitude becomes bigger. It is shown that the variations in the period and the amplitude can be readily explained based on analogy of a spring-mass system. As the initial velocity of the water column increases, the non-linearity of pressure oscillation becomes more noticeable. However, the variations in oscillation characteristics according to the processes of air remain unchanged. The developed code is applied to compare the air cushion effects caused by isentropic and isothermal processes of entrapped air in broken dam flows. Similar tendencies are observed for variations in period and amplitude of pressure oscillations, according to the assumptions on density-pressure relationship of entrapped air in broken dam flows.

Hybrid Cartesian/Immersed Boundary 법을 이용한 2차원 변형날개 주위 점성유동 해석

신상묵(Sangmook Shin),김형태(Hyoung Tae Kim) 대한조선학회 2006 大韓造船學會 論文集 Vol.43 No.5

비대칭 장력 모델을 이용한 예인 물체의 유체-구조 상호작용 모사

신상묵(Sangmook Shin) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.1

The fluid-structure interaction of a towed body is simulated using a developed code, which is based on the flux-difference splitting scheme on the hybrid Cartesian/immersed boundary method. To improve the stability in the coupling between the fluid and structure domains, a scheme is used, in which the effects of structure deformation are treated implicitly. The developed code is validated for the fluid-structure interaction problem through comparisons with other results on the vortex-induced vibration of elastically mounted cylinders. To simulate behavior of a towed body, an asymmetric tension modelling for a towing cable is suggested. In the suggested model, the tension is proportional to the elongation of the cable, but the cable has no effect on the body motion whenever the distance between the endpoints of the cable is smaller than the original length of the cable. The fluid-structure interactions of a towed body are simulated on the basis of different parameters of the towing cables. It is observed that the suggested tension model predicts the snapping for a shorter towing cable, which is in accordance with the reported results.