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케이블-수중 예인체 시스템의 3차원 비선형 완전 연성해석
고광수(Gwangsoo Go),이은택(Euntaek Lee ),안형택(Hyung Taek Ahn) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.6
In this paper, a strongly coupled method for investigating the interaction between a cable and tow-fish is presented. The nodal position finite element method was utilized to analyze the nonlinear cable dynamics, and 6DOF equations of motion were employed to describe the 3D rigid body motion of the tow-fish. Combining cable and tow-fish systems into a single formulation allowed the two nonlinear systems to be strongly coupled into a unified nonlinear system. This strongly coupled system was numerically integrated in the time domain using a predictor/multi-corrector Newmark algorithm. To demonstrate the validity, efficacy, and applicability of the current approach, two different scenarios (virtual and sea trial) were simulated, and the simulation results were validated using the physical plausibility and the sea trial test.
시뮬레이션 기반 수중 운동체의 유체력 미계수 결정 및 6자유도 운동해석
고광수(Gwangsoo Go),안형택(Hyung Taek Ahn),안진형(Jin-Hyeong Ahn) 한국해양공학회 2017 韓國海洋工學會誌 Vol.31 No.5
This paper introduces a simulation-based determination method for hydrodynamic derivatives and 6DOF (degrees-offreedom) motion analysis for an underwater vehicle. Hydrodynamic derivatives were derived from second-order modulus expansion and composed of the added mass, and linear and nonlinear damping coefficients. The added mass coefficients were analytically obtained using the potential theory. All of the linear and nonlinear damping coefficients were determined using CFD simulation, which were performed for various cases based on the actual operating condition. Then, the linear and nonlinear damping coefficients were determined by fitting the CFD results, which referred to 6DOF forces and moments acting on an underwater vehicle, with the least square method. To demonstrate the applicability of the current study, 6DOF simulations for three different scenarios (L-, U-, and S-turn) were carried out, and the results were validated on the basis of physical plausibility.
직교격자 기반 비압축성 솔버(ULSAN3D-Cart) 소개
고광수(Gwangsoo Go),안형택(Hyung Taek Ahn) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
The Cartesian grid based-incompressible flow solver, namely ULSAN3D-Cart, is introduced in this paper. ULSAN3D-Cart involves two algorithm breakthroughs for Cartesian mesh-based flow simulations. The first is a novel efficient and reliable determination procedure of the signed distance function (SDF) based on an adaptive mesh refinement (AMR) strategy. In order to represent the body shape in Cartesian mesh, the SDF, which is 0 at the interface, positive at the exterior, negative at the interior, should be computed instead of grid generation. This new AMR-based algorithm proved to be an order of magnitude faster than a naive SDF computation on a uniform mesh. The second is an application of geometric multigrid on arbitrary complex domain. The geometric multigrid is known as the fastest solution algorithm for elliptic-type boundary value problems on regular domain. However, it is not clear whether geometric multigrid is the fastest on irregular domain or not. Based on current study, we confirmed that the optimal convergence, i.e. O(N) complexity, of multigrid was obtained on irregular domain as well. To demonstrate applicability of current solution algorithm, well-known benchmark problems were solved, and all results were validated by previous experimental and computational results.