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Hertz-Mindlin 접촉 모델이 적용된 음해적 입자법을 통한 다물체 충돌해석
이완기(Wan Ki Lee),김기덕(Gi Deok Kim),변제윤(Je Yun Byun),주영석(Young Suk Joo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Existing Smoothed particle hydrodynamics(SPH) structural analysis model has two problems: tensile instability resulting in particle clumping and the use of non-physical artificial stress. In this study, to solve the above two issues, the structural analysis is implemented with total Lagrangian based corotated SPH, and the Hertz-Mindlin contact model is applied as the interface condition for collision of multi-body. For numerical validation of structural analysis model, dynamic behavior simulation of cantilever beam is performed. Transient analysis of deflection at the cantilever beam tip is conducted, and maximum deflection and frequency are calculated and compared with finite element method(FEM) results and analytical solution. For numerical validation of collision model, transient analysis for reaction force between two elastic rings is performed. The stress distribution and deformation shape at specific time steps are compared with the FEM results.
Total Lagrangian 기반 음해적 입자법을 이용한 외팔보 동적 거동 해석
이완기(Wan Ki Lee),주영석(Young Suk Joo),김진현(Jin Kim) 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.5
SPH(smoothed particle hydrodynamics)는 Lagrangian 기반 수치해석 기법이며 입자를 단위로 사용하는 무격자 방식이다. 기존 SPH 기법으로 구현된 구조해석은 두 가지 문제점을 가지고 있다. 대변형 지점에서 인장불안정으로 인한 입자 겹침 문제와 수치적 민감성으로 인하여 작은 해석간격을 사용하는 문제이다. 본 연구에서는 total Lagrangian 기반 SPH 기법으로 구조해석을 구현하여 인장불안정 문제를 해소한다. 그리고 동회전성 커널함수를 사용하고 탄성력 연산을 음해적으로 수행하여 보다 큰 해석간격을 사용하여도 해석이 발산하지 않도록 한다. 외팔보 동적 거동 해석을 수행하여 수치모델 정확성을 검증하고 구조해석 적용 가능성을 확인한다. Smoothed particle hydrodynamics (SPH) is a particle-based meshless Lagrangian numerical method. The status quo SPH-based structural analysis has two problems: overlapping particles at large deformation points owing to tensile instability and marginal limits on the time-step size owing to the inherent numerical sensitivity. In this study, a total Lagrangian SPH method is employed in the structural analysis to solve the tensile instability problem. In addition, simulation divergence is prevented even when a relatively larger time-step is used by performing a numerical analysis implicitly and using a corotated kernel function. Dynamic analyses of cantilever beams are performed to verify the accuracy of the numerical model presented in this study and its applicability to structure analysis.
3차원 유동장 해석을 통한 LNG 선박용 극저온 글로브 밸브 유동특성 및 케비테이션 연구
이완기(Wan Ki Lee),김문기(Moon Ki Kim),최재붕(Jae Boong Choi) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
The main functions of globe valve are to shut off and control the fluid flow. Globe valve has high airtightness, but there is a disadvantage like large pressure loss. So globe valve is mainly used as a high pressure valve. In this paper, among the globe valves with various purpose, the globe valve used in LNG marine engine system was selected for the research. There are total of 6 different models with different valve sizes. Computational fluid dynamics(CFD) analysis was conducted by varying the valve opening rate for each valve model. From the analysis results, the pressure drop and cavitation number in valve were calculated. Also, vapor volume fraction contour was obtained. The cavitation index is a indicator that predicts the occurrence of cavitation, and the closer to 1, the higher probability of cavitation. A high correlation was confirmed by comparing cavitation index and occurrence of cavitation.