• Title/Summary/Keyword: Reinitialization

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Study on the Solution of Reinitialization Equation for Level Set Method in the Simulation of Incompressible Two-Phase Flows (비압축성 2 상유동의 모사를 위한 Level Set 방법의 Reinitialization 방정식의 해법에 관한 연구)

  • Cho, Myung-Hwan;Choi, Hyoung-Gwon;Yoo, Jung-Yul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.10
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    • pp.754-760
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    • 2008
  • Computation of moving interface by the level set method typically requires the reinitialization of level set function. An inaccurate estimation of level set function $\phi$ results in incorrect free-surface capturing and thus errors such as mass gain/loss. Therefore, an accurate and robust reinitialization process is essential to the simulation of free-surface flows. In the present paper, we pursue further development of the reinitialization process, which evaluates level set function directly using a normal vector on the interface without solving there-distancing equation of hyperbolic type. The Taylor-Galerkin approximation and P1P1 splitting/SUPG (Streamline Upwind Petrov-Galerkin) FEM are adopted to discretize advection equation of the level set function and the incompressible Navier-Stokes equation, respectively. Advection equation and re-initialization process of free surface capturing are validated with benchmark problems, i.e., a broken dam flow and timereversed single vortex flow. The simulation results are in good agreement with the existing results.

Study on the direct approach to reinitialization in using level set method for simulating incompressible two-phase flows (비압축성 2 상유동의 모사를 위한 level set 방법에서의 reinitialization 직접 접근법에 관한 연구)

  • Cho, Myung-H.;Choi, Hyoung-G.;Yoo, Jung-Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.568-571
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    • 2008
  • The computation of moving interface by the level set method typically requires reinitializations of level set function. An inaccurate estimation of level set function ${\phi}$ results in incorrect free-surface capturing and thus errors such as mass gain/loss. Therefore, accurate and robust reinitialization process is essential to the free-surface flows. In the present paper, we pursue further development of the reinitialization process, which evaluates directly level set function ${\phi}$ using a normal vector in the interface without solving the re-distancing equation of hyperbolic type. The Taylor-Galerkin approximation and P1P1splitting FEM are adopted to discretize advection equation of the level set function and the Navier-Stokes equation, respectively. Advection equation of free surface and re-initialization process are validated with benchmark problems, i.e., a broken dam flow and time-reversed single vortex flow. The simulation results are in good agreement with the existing results.

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FINITE ELEMENT ANALYSIS OF LEVEL SET FORMULATION (유한요소법을 이용한 level set 공식화의 해석)

  • Choi, H.G.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.223-227
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    • 2009
  • In the present study, a least square weighted residual method and Taylor-Galerkin method were formulated and tested for the discretization of the two hyperbolic type equations of level set method; advection and reinitialization equations. The two approaches were compared by solving a time reversed vortex flow and three-dimensional broken dam flow by employing a four-step splitting finite element method for the solution of the incompressible Navier-Stokes equations. From the numerical experiments, it was shown that the least square method is more accurate and conservative than Taylor-Galerkin method and both methods are approximately first order accurate when both advection and reinitialization phase are involved in the evolution of free surface.

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Study on the Phase Interface Tracking Numerical Schemes by Level Set Method (Level Set 방법에 의한 상경계 추적 수치기법 연구)

  • Kim, Won-Kap;Chung, Jae-Dong
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.116-121
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    • 2006
  • Numerical simulations for dendritic growth of crystals are conducted in this study by the level set method. The effect of order of difference is tested for reinitialization error in simple problems and authors founded in case of 1st order of difference that very fine grids have to be used to minimize the error and higher order of difference is desirable to minimize the reinitialization error The 2nd and 4th order Runge-Kutta scheme in time and 3rd and 5th order of WENO schemes with Godunov scheme are applied for space discretization. Numerical results are compared with the analytical theory, phase-field method and other researcher's level set method.

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A Study on a VOF Method for Improved Free Surface Capturing (VOF법의 자유수면 포착정도 향상을 위한 연구)

  • Park Il-Ryong;Kim Wu-Joan;Kim Jin;Van Suak-Ho
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.202-206
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    • 2005
  • A new numerical scheme for two-phase flows, the Hybrid VOF method has been developed for improved free surface capturing. The present new method is a volume capturing based VOF method coupled with a reinitialization procedure of a Level-set method. For validation, the proposed method is applied to two test cases: spherical bubble rising and dam breaking. The calculated results by using the Hybrid VOF method with the two previously applied VOF formulations are compared with available numerical and experimental data. It is found that the new method provides more accurate results than the two previous ones.

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A Study on a VOF Method for the Improvement of Free Surface Capturing (VOF 법의 자유수면 포착정도 향상을 위한 연구)

  • Park, Il-Ryong;Kim, Wu-Joan;Kim, Jin;Van, Suak-Ho
    • Journal of the Society of Naval Architects of Korea
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    • v.42 no.2 s.140
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    • pp.88-97
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    • 2005
  • A new numerical scheme solving two-phase flow, the Hybrid VOF method for improved free surface capturing has been developed by combining a volume capturing VOF method with the Level-Set reinitialization procedure. For validation, the proposed method is applied to 3-D bubble rising problem, dam breaking and the free surface flow around a commercial container ship. The calculated results by using the Hybrid VOF method with the two previously applied VOF formulations are compared with available numerical and experimental data. It is found that the new method provides more reasonable results than the two previous ones.

Modified harmony search and its application to cost minimization of RC columns

  • Medeiros, Guilherme F.;Kripka, Moacir
    • Advances in Computational Design
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    • v.2 no.1
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    • pp.1-13
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    • 2017
  • This paper presents a variant of the Harmony Search Algorithm (HS) and its application to discrete optimization. The main proposed modifications regarding original HS are related to stopping criterion and reinitialization of population, called Harmony Memory. In order to investigate the efficiency of the algorithm, it was applied for obtaining optimal sections of reinforced concrete columns subjected to uniaxial flexural compression. To minimize the cost of the section, the amount and diameters of the reinforcement bars and the dimensions of the columns cross sections were considered as design variables. The obtained results were compared to those generated by other optimization methods. Since, to the examples, Harmony Search reached the same results achieved by Simulated Annealing, some additional analysis are presented in order to compare these methods regarding success rate and number of iterations to reach the optimum.

Development of Robust Adaptive Learning Control for Nonlinear System (비선형 시스템에 대한 강인성 적응 학습 제어기의 개발)

  • Yu, Yeong-Sun;Ha, Hwan-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.12
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    • pp.1895-1902
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    • 2001
  • This paper gives an overview of the relationships between methods of loaming and adaptive control. It is the objective of this paper to develop adaptive learning control algorithms that combine the advantages of adaptive control with those of leaning control to the extent possible for the type of system model used. The robustness of this adaptive loaming control with respect to reinitialization errors and fluctuation of dynamics from disturbance is analyzed extensively. Simulation results have shown to verify the effectiveness of the proposed control algorithm.

Visual Object Tracking based on Real-time Particle Filters

  • Lee, Dong- Hun;Jo, Yong-Gun;Kang, Hoon
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.1524-1529
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    • 2005
  • Particle filter is a kind of conditional density propagation model. Its similar characteristics to both selection and mutation operator of evolutionary strategy (ES) due to its Bayesian inference rule structure, shows better performance than any other tracking algorithms. When a new object is entering the region of interest, particle filter sets which have been swarming around the existing objects have to move and track the new one instantaneously. Moreover, there is another problem that it could not track multiple objects well if they were moving away from each other after having been overlapped. To resolve reinitialization problem, we use competitive-AVQ algorithm of neural network. And we regard interfarme difference (IFD) of background images as potential field and give priority to the particles according to this IFD to track multiple objects independently. In this paper, we showed that the possibility of real-time object tracking as intelligent interfaces by simulating the deformable contour particle filters.

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Level set method for the simulation of rising bubble based on triangular and Quadrilateral elements (삼각형 요소와 사각형 요소에 기초한 상승기포의 모사를 위한 Level set 방법)

  • Cho, M.H.;Choi, H.G.;Jeon, B.J.;Yoo, J.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.10-13
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    • 2011
  • A level set method is proposed to simulate the incompressible two-phase flow considering the effect of surface tension. For reinitialization of level set junction, a direct approach method is employed, instead of solving hyperbolic type equation. A mixed element is adopted, so that the continuity mid Navier-Stokes equations are solved by using the quadratic elements (six-node triangular element mid nine-node quadrilateral element), mid the level set function is solved by using the linear elements (three-node triangular element mid four-node quadrilateral element). In order to verify the accuracy mid robustness of the codes, the present methods are applied to a few benchmark problems. It is confirmed that the present results are in good qualitative mid quantitative agreements with the existing studies.

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