• Title/Summary/Keyword: 유한체적법

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A study on application of GPU-accelerated kinematic wave rainfall-runoff model (GPU 가속 운동파 강우유출모형의 적용 연구)

  • Kim, Boram;Yun, Gwan Seon;Kim, Hyeong-Jun;Yoon, Kwang Seok
    • Proceedings of the Korea Water Resources Association Conference
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    • 2020.06a
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    • pp.323-323
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    • 2020
  • 그래픽 처리 장치(Graphic Processing Unit: GPU)는 그래픽 처리 작업에 특화된 다수의 산술논리 장치(Arithmetic Logic Unit: ALU)로 구성되어 있어서 중앙 처리 장치(Central Processing Unit: CPU)보다 한 번에 더 많은 연산 수행이 가능하다. 본 연구는 GPU 가속 운동파모형을 실제 유역에 적용하여, GPU 가속 운동파 강우유출모형 결과에 대한 정확성과 연산 소요 시간에 대한 효율성을 확인하였다. GPU 가속 운동파모형은 분포형 강우유출모형의 수치모의 연산시간을 단축시키기 위해 CUDA 포트란을 이용하여 개발되었다. 분포형모형의 지배방정식은 운동파모형과 Green-Ampt모형으로 구성되었고, 운동파모형은 유한체적법을 이용하여 이산화 하였다. GPU 가속 운동파모형을 이용하여 금강의 미호천 유역에서 발생하는 강우유출현상을 모의 하였고, 동일한 유한체적법을 이용한 CPU(Central Processing Unit) 기반의 강우유출모형과 비교하였다. 그 결과 GPU 가속모형의 결과는 미호천 유역 하류단에서 관측한 결과와 유사한 결과를 나타냈다. 또한, 연산소요시간은 CPU 기반의 강우유출모형의 연산소요시간보다 단축되었으며, 본 연구에 사용된 장비를 기준으로 최대 100배 정도 단축되었다.

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Analysis of Shallow-Water Equations with HLLC Approximate Riemann Solver (HLLC Approximate Riemann Solver를 이용한 천수방정식 해석)

  • Kim, Dae-Hong;Cho, Yong-Sik
    • Journal of Korea Water Resources Association
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    • v.37 no.10
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    • pp.845-855
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    • 2004
  • The propagation and associated run-up process of nearshore tsunamis in the vicinity of shorelines have been analyzed by using a two-dimensional numerical model. The governing equations of the model are the nonlinear shallow-water equations. They are discretized explicitly by using a finite volume method and the numerical fluxes are reconstructed with a HLLC approximate Riemann solver and weighted averaged flux method. The model is applied to two problems; The first problem deals with water surface oscillations, while the second one simulates the propagation and subsequent run-up process of nearshore tsunamis. Predicted results have been compared to available analytical solutions and laboratory measurements. A very good agreement has been observed.

Analysis of Radiative Heat Transfer about a Circular Cylinder in a Crossflow by P-l Approximation and Finite Volume Method in Non-Orthogonal Coordinate System (비직교좌표계에 대한 P-1 근사법 및 유한체적법을 이용한 주유동 중의 원형실린더 주위의 복사열전달 해석)

  • 이공훈;이준식;최만수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.3
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    • pp.806-819
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    • 1995
  • A study of radiative heat heat transfer has been done in the non-orthogonal coordinate system utilizing the finite volume method and the P.1 approximation. Radiation of absorbing, emitting and scattering media in a concentric annulus has been solved using the non-orthogonal coordinate and the calculations were compared with the existing results. The results obtained from the analysis using the finite volume method are in good agreement with the existing calculations for all optical thicknesses. It was also shown that for only optically thick cases, P-1 approximation can be used in a non-orthogonal coordinate. Convective heat transfer analysis has been carried out to obtain the temperature fields in a cross flow around a circular cylinder and the finite volume method was applied in the non-orthogonal coordinate system to analyze radiative heat transfer. Effects of the optical thickness, the ratio of the surface temperature of the cylinder tot he free stream temperature, and the scattering albedo on radiation have been presented.

Unstructured Finite-Volume Analysis of Vaporization Characteristics of Fuel Droplets in Laminar Flow Field (비정렬 유한체적법을 이용한 유동장 내의 연료액적 증발 특성 해석)

  • Kim, T.J.;Kim, Y.M.;Sohn, J.L.
    • Journal of ILASS-Korea
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    • v.5 no.1
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    • pp.13-22
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    • 2000
  • The present study has numerically analyzed the vaporization characteristics of fuel droplets in the high temperature convective flow field. The axisymmetric governing equations for mass, momentum, energy, and species are solved by an iterative and implicite unstructured finite-volume method. The moving boundary due to vaporization is handled by the deformable unstructured grid technique. The pressure-velocity coupling in the density-variable flows is treated by the SIMPLEC algorithm. In terms of the matrix solver, Bi-CGSTAB is employed for the numerically efficient and stable convergence. The n-decane is used as a liquid fuel and the initial droplet temperature is 300K. Computations are performed for the nonevaporating and evaporating droplets with the relative interphase velocity(25m/s). The unsteady vaporization process has been simulated up to the nondimensional time, 25. Numerical results indicate that the mathematical model developed in this study succesfully simulates the main features of the droplet vaporization process in the convective environment.

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Analysis of Laminar Flows around Submerged Spheres (물 밑에 잠긴 구 주위의 층류 유동장 해석)

  • Kwag, Seung-Hyun
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.8
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    • pp.1094-1099
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    • 2010
  • Three dimensional laminar flows are numerically simulated around the submerged spheres. The finite volume based Navier-Stokes equations with unstructured grids are solved to make clear the hydrodynamic phenomena near and far away from the body. Reviews are made on with the vorticity, velocity, dynamic pressure, residuals, drags, etc. The Reynolds numbers under consideration are 425, 300, 250 and 100. In case of small spacing between spheres, the flow is more stable than that past a single sphere. According to the analysis, the flow past two spheres is found to be unstable as the spacing becomes larger. The rear sphere shows the deduction of stagnation pressure, which results in the decrease of the resistance. The predicted drag coefficients verify that the present numerical calculation is reasonable.

A Study on the Cooling Parameter Decision of Linear Motor System by Finite Volume Method (유한체적법을 이용한 리니어모터 시스템의 냉각조건 선정에 관한 연구)

  • Hwang Y.K.;Eun I.E.;Lee C.M.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2006.05a
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    • pp.449-450
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    • 2006
  • Development of a feed drive system with high speed, positioning accuracy and thrust has been an important issue in modern automation systems and machine tools. Linear motors can be used as an efficient system to achieve such technical demands. By eliminating mechanical transmission mechanisms such as ball screw or rack-pinion, much higher speeds and greater acceleration can be achieved without backlash or excessive friction. However, an important disadvantage of linear motor system is its high power loss and heating up of motor and neighboring machine components on operation. For the application of the linear motors to precision machine tools an effective cooling method and thermal optimizing measures are required. In this paper presents an investigation into a thermal behavior of linear motor cooling plate. FVM employed to analyze the thermal behavior of the linear motor cooling plate, using the ANSYS-CFX.

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Development of Computational Methods for Viscous Flow around a Commercial Ship Using Finite-Volume Methods (유한체적법을 이용한 상선주위의 난류유동 계산에 관한 연구)

  • Wu-Joan Kim;Do-Hyun Kim;Suak-Ho Van
    • Journal of the Society of Naval Architects of Korea
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    • v.37 no.4
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    • pp.19-30
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    • 2000
  • A finite-volume method is developed to solve turbulent flows around modern commercial hull forms with bow and stern bulbs. The RANS equations are solved. The cell-centered finite-volume method employs QUICK and central difference scheme for convective and diffusive flux discretization, respectively. The SIMPLEC method is adopted for the velocity-pressure coupling. The developed numerical methods are applied to calculate turbulent flow around KRISO 3600TEU container ship. Surface meshes are generated into five blocks: bow and stern bulbs, overhang, fore and afterbody. 3-D field grid system with O-H topology is generated using elliptic grid generation method. Surface friction lines and wake distribution at propeller plane is compared with experiment. The calculated results show that the present method can be used to predict flow around a modern commercial hull forms with bulbs.

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An anisotropic mesh refinement for an unstructured finite volume method (비정렬 유한 체적법을 위한 비등방 격자 미세화 기법)

  • Lee K. S.;Baek J. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.03a
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    • pp.77-82
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    • 2004
  • A new anisotropic mesh refinement method is proposed. The new method is based on a simple second order interpolation error indicator. Therefore, it is methodologically direct and intuitive as compared with traditional anisotropic refinement strategies. Moreover, it does not depend on the mesh type. The error indicator is face-wisely calculated for all faces in a mesh and the cell refinement type is determined by the configuration of face markings with a given threshold. For the sake of simplicity, an application for a poisson equation on a triangle mesh is considered. The error field and resultant mesh refinement pattern are compared and effects of the threshold selection are discussed. Applying anisotropic refinement with various thresholds, we observed higher convergence rates than those in the uniform refinement cases.

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An unstructured finite volume method for unsteady incompressible flows with full second order accuracy (2차 정확도를 가지는 비정상 비압축성 유동장 해석을 위한 비정렬 유한 체적법의 개발)

  • Lee K. S.;Baek J. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.03a
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    • pp.71-76
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    • 2004
  • An extension of our recently developed locally linear reconstruction scheme to 2 dimensional incompressible flow solver is presented. The solver is based on a semi-implicit fractional step method in which the convective term is discretized by Adams-Bashforth method and the diffusion term by Crank-Nicolson method. Several numerical examples are tested to demonstrate the mesh type independent accuracy of the solver, which include decaying vortex flow, square cavity flow, and flow around a circular cylinder. The above examples are solved on quadrilateral or hybrid meshes. For all numerical examples, we obtained reasonable results.

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Analysis of Boltzmann transport equation with Finite Volume Method at Spherical coordinate (유한체적법을 통한 구면 좌표계에서의 볼츠만 수송방정식의 해석)

  • Oh, Hyuck-Keun;Jin, Jae-Sik;Lee, Joon-Sik
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1800-1805
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    • 2008
  • A "finite volume method" is proposed to predict heat transport in a spherical enclosure at micro/nanoscale with the Boltzmann transport equation (BTE). The gray version of the BTE with the relaxation time approximation has been applied. Pointing out similarity between radiative transfer equation (RTE) and BTE, the mapping process in RTE is adopted to treat the angular derivative term and linear algebraic discretization equation is derived by using the established method which is used in 2-D BTE in cartesian coordinates. The simulation results are compared to exact solution to RTE for various acoustic thicknesses and ratio of radii. The comparison shows that this method is logical and accurate, and it is possible to easily adopt various models in spherical BTE.

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