• Title/Summary/Keyword: unstructured finite volume model

Search Result 66, Processing Time 0.024 seconds

Calculation of overtopping discharge with time-dependent aspects of an embankment failure (시간에 따른 제방붕괴 양상을 고려한 월류량 산정)

  • Kim, Hyung-Jun;Kim, Jong-Ho;Jang, Won-Jae;Cho, Yong-Sik
    • Journal of the Korean Society of Hazard Mitigation
    • /
    • v.7 no.3
    • /
    • pp.69-78
    • /
    • 2007
  • In this study, a time-dependent aspect of an embankment failure is considered to simulate a flood inundation map and calculate overtopping discharge induced by an embankment failure. A numerical model has been developed by solving the two dimensional nonlinear shallow water equations with a finite volume method on unstructured grids. To analyze a Riemann problem, the HLLC approximate Riemann solver and the Weighted Averaged Flux method are employed by using a TVD limiter and the source term treatment is also employed by using the operator splitting method. Firstly, the numerical model is applied to a dam break problem and a sloping seawall. Obtained numerical results show good agreements with experimental data. Secondly, the model is applied to a flow induced by an embankment failure by assuming that the width and elevation of embankment are varied with time-dependent functions. As a result of the comparison with each numerical overtopping discharge, established flood inundation discharges in the previous studies are overestimated than the result of the present numerical model.

Flamelet Modelling of Soot Formation and Oxidation in a Laminar $CH_4-Air$ Diffusion Flame (화염편 모델을 이용한 층류확산화염장의 매연 생성 및 산화과정 해석)

  • Kim Gunhong;Kim Hoojoong;Kim Yongmo
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.13 no.1
    • /
    • pp.68-75
    • /
    • 2005
  • By utilizing a semi-empirical soot model, the applicability of the laminar flamelet concept fur simulating the formation and oxidation of soot in the laminar diffusion flame has been studied. The source terms for two transport equations of the soot formation and oxidation are calculated in the mixture fraction/scalar dissipation rate space for laminar flamelets and stored in a library. In this study, emphasis is given to the interaction associated with radiation and soot formation. The radiative heat loss is obtained by solving the radiative transfer equation using the unstructured grid finite volume method with the WSGGM. The calculated temperatures and soot volume fractions agree relatively well with the experimental data and the previous numerical results of Kaplan et al. using the detailed chemistry.

Flow and Aerodynamic Characteristics Analyses of A Commercial Passenger Airplane (상용 여객기의 유동 및 공력 특성 해석)

  • Kim, Yang-Kyun;Kim, Sung-Cho;Kim, Jeong-Soo;Ree, Kee-Man;Jin, Hak-Su
    • Proceedings of the KSME Conference
    • /
    • 2007.05b
    • /
    • pp.2857-2861
    • /
    • 2007
  • Flow and aerodynamic characteristics were analyzed numerically for a commercial passenger airplane, Boeing 747-400, flying in the cruising condition. The model geometry with 100:1 in scale was obtained by the photo scanning measurement with the maximum error of 1.4% comparing with the real airplane dimension. The three-dimensional inviscid steady compressible governing equations were solved by the finite volume method in the unstructured grid system. The convective terms were treated by the Crank-Nicholson and first-order upwind schemes. In the computational results, the strong wing-tip vortices were clearly observed and the pressure contours on the airplane surface were suggested. The lift and drag forces in the wing with engines increase by 1.49% and 3.9%, respectively compared with the case without engines. The aerodynamic forces were estimated quantitatively for each element which consists of the airplane.

  • PDF

Design of An Axial Flow Fan with Shape Optimization (형상 최적화를 통한 축류송풍기의 설계)

  • Seo Seoung-Jin;Choi Seung-Man;Kim Kwang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.30 no.7 s.250
    • /
    • pp.603-611
    • /
    • 2006
  • This paper presents the response surface optimization method using three-dimensional Wavier-Stokes analysis to optimize the blade shape of an axial flow fan. Reynolds-averaged Wavier-Stokes equations with $k-{\epsilon}$ turbulence model are discretized with finite volume approximations using the unstructured grid. Regression analysis is used for generating response surface, and it is validated by ANOVA and t-statistics. Four geometric variables, i.e., sweep and lean angles at mean and tip respectively were employed to improve the efficiency. The computational results are compared with experimental data and the comparisons show generally good agreements. As a main result of the optimization, the total efficiency was successfully improved. Also, detailed effects of sweep and lean on the axial flow fan are discussed.

Numerical Solutions of Compressible Navier-Stokes Equations on Hybrid Meshes Using Newton-GMRES Method (Newton-GMRES 법을 사용한 혼합격자에서의 압축성 Navier-Stoke 방정식 수치 해석)

  • Choi Hwan-Seok
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2000.05a
    • /
    • pp.178-183
    • /
    • 2000
  • An efficient Newton-GMRES algorithm is presented for computing two-dimensional steady compressible viscous flows on unstructured hybrid meshes. The scheme is designed on cell-centered finite volume method which accepts general polygonal meshes. Steady-state solution is obtained with pseudo-transient continuation strategy. The preconditioned, restarted general minimum residual(GMRES) method is employed in matrix-free form to solve the linear system arising at each Newton iteration. The incomplete LU fartorization is employed for the preconditioning of linear system. The Spalart-Allmars one equation turbulence model is fully coupled with the flow equations to simulate turbulence effect. The accuracy, efficiency and robustness of the presently developed method are demonstrated on various test problems including laminar and turbulent flows over flat plate and airfoils.

  • PDF

NUMERICAL MODELING FOR FLAME STABILIZATION OF GAS TURBINE COMBUSTOR (가스터빈 엔진의 화염안정성에 대한 수치모델링)

  • Kang Sungmo;Kim Yongmo;Chung Jae-Hwa;Ahn Dal-Hong
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2005.10a
    • /
    • pp.201-206
    • /
    • 2005
  • In order to realistically represent the complex turbulence-chemistry interaction at the partially premixed turbulent lifted flames encountered in the gas turbine combustors, the combined conserved-scalar/level-set flamelet approach has been adopted. The parallel unstructured-grid finite-volume method has been developed to maintain the geometric flexibility and computational efficiency for the solution of the physically and geometrically complex flows. Special emphasis is given to the swirl effects on the combustion characteristics of the lean-premixed gas turbine combustor. Numerical results suggest that the present approach is capable of realistically simulating the combustion characteristics for the lean-premixed gas turbine engines and the lifted turbulent jet flame with a vitiated coflow.

  • PDF

Three-Dimensional Numerical Analysis on Recirculation Generated by Obstacles Around a Cooling Tower (냉각탑 주위 장애물에 의한 재순환 현상에 관한 3차원 수치해석)

  • Choi, Young-Ki
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.33 no.4
    • /
    • pp.225-234
    • /
    • 2009
  • The present study has been preformed to investigate the effect of obstacles around a cooling tower with air-guide to prevent recirculation. The external region as well as the cooling tower are included in the computational domain to analyze the flow phenomena around a cooling tower accurately. Three-dimensional analysis is performed using the finite volume method with non-orthogonal and unstructured grid system. The standard turbulence model is used to consider the turbulence effect. In order to investigate the recirculation phenomena, flow and temperature fields are calculated with the distance between cooling tower and obstacle, the allocated geometrical type and the air-guide. The moisture fraction rates decrease with increment of the distance between cooling tower and obstacle. The effect of air-guide to reduce the mean recirculation rate is obviously observed.

A Parametric Study on Inlet Duct Treatment for Improving the Operational Stability of a Centrifugal Compressor (운전안정성 향상을 위한 원심 압축기의 유입부 형상변화에 관한 연구)

  • Seo, Tae-Wan;Heo, Man-Woong;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
    • /
    • v.19 no.5
    • /
    • pp.12-19
    • /
    • 2016
  • In present study, a parametric study of a centrifugal compressor with inlet treatment has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model was used for analysis of turbulence. The finite volume method and unstructured grid system were used for the numerical solution. Tested parameters were related to the geometry of the inlet duct. It was found that the application of circumferentially distributed holes in the inlet duct improves operational stability of the compressor compared to that with conventional inlet duct.

DEVELOPMENT OF CAVITATING FLOW ANALYSIS CODE (캐비테이팅 유동 해석 코드 개발)

  • Yang, Seung-Yong;Myong, Hyon-Kook
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2010.05a
    • /
    • pp.122-126
    • /
    • 2010
  • The Rayleigh Plesset based cavitation model(Singhal et al., 2002) is reproduced through a pressure-based finite-volume numerical method using unstructured hexagonal mesh, which is developed by the author. In the process of reproduction, a mass conservation problem by the large density changes associated with phase change, which wasn't mentioned by them, has been exposed. One resolution about it is proposed and then cavitating flow characteristics around a hydrofoil (NACA66) for evaluation of the code are investigated. The computational results are verified by the comparison with the experimental results and show good agreements with them.

  • PDF

Geometry Realization of an Airplane and Numerical Flow Visualization (역설계에 의한 비행기의 형상 구현과 수치계산에 의한 유동 가시화)

  • Kim, Yang-Kyun;Kim, Sung-Cho;Kim, Jeong-Soo;Choi, Jong-Wook;Park, Jeong
    • Journal of the Korean Society of Visualization
    • /
    • v.5 no.2
    • /
    • pp.20-25
    • /
    • 2007
  • The geometry of a commercial passenger airplane is realized based on a Boeing 747-400 model through the photographic scanning and reverse engineering. The each element consisting of the plane such as fuselage, wing, vertical fin, stabilizer and engines, is individually generated and then the whole body is assembled by the photomodeler. The maximum error in the realized airplane is about 1.4% comparing with the real one. The three-dimensional inviscid steady compressible governing equations are solved in the unstructured tetrahedron grid system, and in a finite volume method using STAR-CD when the airplane flies at the cruise condition. The pressure distribution on the surface and the wing-tip vortices are visualized, and in addition to the aerodynamics coefficients, lift and drag are estimated.