• Title/Summary/Keyword: computational fluids dynamics

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NUMERICAL SIMULATION OF HIGH-SPEED FLOWS WITH SHOCK WAVE TURBULENT BOUNDARY LAYER INTERACTIONS (충격파와 난류경계층의 상호작용에 대한 수치해석)

  • Moon S. Y.;Sohn C. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2000.05a
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    • pp.51-59
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    • 2000
  • The Interactions of shock wave with turbulent boundary layers in high-speed flows cause complex flowfields which result in increased adverse pressure gradients, skin friction and temperature. Accurate and reliable prediction of such phenomena is needed in designing high-speed propulsion systems. Such analyses of the complex flowfields require sophisticated numerical scheme that can resolve interactions between shock wave and boundary layers accurately. Therefore the purpose of the present. article is to introduce an accurate and efficient mixed explicit-implicit generalized Galerkin finite element method. To demonstrate the validity of the theory and numerical procedure, several benchmark cases are investigated.

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STUDY OF THREE-DIMENSIONAL DETONATION WAVE STRUCTURES USING PARALLEL PROCESSING (병렬 처리를 이용한 3차원 데토네이션 파 구조 해석)

  • Cho D.R.;Choi J.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.151-155
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    • 2005
  • Three-dimensional structures of unsteady detonation wave propagating through a square-shaped tube is studied using computational method and parallel processing. Inviscid fluid dynamics equations coupled with variable-${\gamma}$ formulation and simplified one-step Arrhenius chemical reaction model were analysed by a MUSCL-type TVD scheme and four stage Runge-Kutta time integration. Results in three dimension show the two unsteady detonation wave propagating mode, the Rectangular and diagonal mode of detonation wave instabilities. Two different modes of instability showed the same cell length but different cell width and the geometric similarities in smoked-foil record.

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NUMERICAL ANALYSIS OF THE GUST GENERATOR FOR KARI LOW SPEED WIND TUNNEL (KARI 중형 아음속 풍동용 돌풍 발생기의 수치해석)

  • Park Y. M.;Kwon K. J.;Lee S. W.;Kim T. W.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.275-279
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    • 2005
  • The vortex convection and induced flow field behind the KARI 3m x 4m LSWT gust generator was computed by using Computational Fluid Dynamics. For the accurate simulation of vortex convection, inviscid, laminar, Spalart-Allmars k-e and k-w turbulence models were tested with the NAL gust generator configuration and Spalart-Allmaras turbulence model was selected for the prediction of induced flow field behind the KARI LSWT gust generator. The wind tunnel test was also carried out at KARI LSWT and the results were compared with CFD prediction.

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CALCULATION OF HYDRODYNAMIC CHARACTERISTICS FOR SHIP'S PROPULSION MECHANISM OF WEIS-FOGH TYPE (Weis-Fogh형 선박추진기구의 유체역학적 특성계산)

  • Ro K.D.;Kang M.H.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.305-310
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    • 2005
  • The velocity and pressure fields of a ship's propulsion mechanism of the Weis-Fogh type, in which a airfoil moves reciprocally in a channel, are studied in this paper using the advanced vortex method. The airfoil and the channel are approximated by a finite number of source and vortex panels, and the free vortices are introduced from the body surfaces. The viscous diffusion of fluid is represented using the core-spreading model to the discrete vortices. The velocity is calculated on the basis of the generalized Biot-Savart low and the pressure field is calculated from integrating the equation given by the instantaneous velocity and vorticity fields. Two-dimensional unsteady viscose flows of this propulsion mechanism are numerically clarified, and the calculated results agree well with the experimental ones.

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Numerical Grid Generation Techniques for Flow Field Configurations. (유동장 형상에 따른 격자구성 기법 연구)

  • Yoon Yong-Hyun
    • 한국전산유체공학회:학술대회논문집
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    • 1995.10a
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    • pp.90-103
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    • 1995
  • The field of computational fluid dynamics(CFD) is rapidly approaching the stage where viscous flows over complex configurations are solved. However, the situation is not as promising when one considers a more complete configuration. CFD is not a banana, but a onion. The difficulties arise mainly because the task of generating the grids for modeling such complex geometries is tedious. The primary interest of the author is in the area of grid generation, in particular, duct flow calculations typically encountered in the internal flow. Pertinent examples will be cited to demonstrate the feasibility of solving viscous flow over practical duct configurations of current interest on grid topologies.

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Intra-luminal Thrombus Reduces Stress in the Aneurysm Wall: Fluid-Structure Interaction in Pulsatile Flow

  • Kim S. Y.;Kim Y. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2003.10a
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    • pp.147-149
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    • 2003
  • Using computational fluid dynamics with the fluid-structure interaction, structural effects of intra-luminal thrombus were determined in thrombosed axisymmetric abdominal aorta aneurysm (AAA) models under pulsatile flow. Four different models, varying dilatations of the aneurysm and Young's moduli of intra-luminal thrombus, were defmed. Compared with unthrombosed AAA models, both von Mises stress and radial displacements in the aneurysm wall significantly decreased. Stiffer intra-luminal thrombus reduced von Mises stress in the aneUtysm wall. The present study supported that intra-luminal thrombus might reduce wall stress in the aneurysm.

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CFD SIMULATIONS OF SOLID/LIQUID TWO-PHASE FLow IN AN AGITATOR (전산유체역학을 이용한 교반기 내부의 고체/액체 다상유동 해석)

  • Kim, Chi-Gyeom;Won, Chan-Shik;Hur, Nahm-Keon
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.27-31
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    • 2007
  • Glass particle distribution in a stirred solid/liquid systems was investigated using computational fluid dynamics(CFD). The numerical results were compared to experimental data from the available literature which investigated the local dispersed phase volume fraction by means of an endoscope technique. Eulerian multi-phase model and applications considered high loading of solid particle was used to investigate the influence of the particle concentration and mixing tank size on the solid distribution. A good agreement was obtained between the experimental data and simulation results. The results showed different solid particle distribution in an agitator by particle concentration and mixer size.

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A NUMERICAL SIMULATION OF THE PRESSURE COEFFICIENT AROUND A CUBIC BUILDING MODEL (수치풍동 기법을 이용한 정사각형 건물 주위의 풍압계수에 관한 연구)

  • Yeo, Jae-Hyun;Hur, Nahm-Keon;Won, Chan-Shik;Kim, Sa-Ryang;Choi, Chang-Koon
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.162-166
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    • 2007
  • In the present study, the pressure coefficient of a cubic building model is numerically simulated. Three turbulence models of standard ${\kappa}-{\varepsilon}$, RNG ${\kappa}-{\varepsilon}$ and LES are adopted and the results are compared with the available experimental data. From the results, it has been found that RNG ${\kappa}-{\varepsilon}$ turbulence model and LES turbulence model were shown to predict fairly well the experimental pressure coefficient. In contrast, the results of the standard ${\kappa}-{\varepsilon}$ turbulence model showed large discrepancies in pressure coefficient on the side and top surfaces of the cubic building, which limits the applicability of the standard ${\kappa}-{\varepsilon}$ turbulence model on wind engineering.

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IMMERSED BOUNDARY METHOD FOR THE ANALYSIS OF 2D FLOW OVER A CYLINDER AND 3D FLOW OVER A SPHERE (원통 주위의 2차원 유동과 구 주위의 3차원 유동해석을 위한 가상경계법 개발)

  • Fernandes, D.V.;Suh, Y.K.;Kang, S.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.194-199
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    • 2007
  • IB (immersed boundary) method is one of the prominent tool in computational fluid dynamics for the analysis of flows over complex geometries. The IB technique simplyfies the solution procedure by eliminating the requirement of complex body fitted grids and it is also superior in terms of memory requirement. In this study we have developed numerical code (FOTRAN) for the analysis of 2D flow over a cylinder using IB technique. The code is validated by comparing the wake lengths and separation angles given by Guo et. al. We employed fractional-step procedure for solving the Navier-Stokes equations governing the flow and discrete forcing IB technique for imposing boundary conditions. Also we have developed a 3D code for the backward-facing-step flow and flow over a sphere. The reattachment length in backward-facing-step flow was compared with the one given by Nie and Armaly, which has proven the validity of our code.

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A COMPUTIONAL STUDY ON PERFORMANCE OF THE DENTAL AIR MOTOR HAND-PIECE (치과 치료기기용 에어 모터 핸드피스의 성능에 관한 수치 해석적 연구)

  • Sung, Y.J.;Lim, S.;Song, D.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.277-282
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    • 2010
  • Imported vane type air motor and-piece is used widely in the domestic dental services. The imported hand-pieces are more than 90 percent in the domestic market. The air-motor unit of the hand-piece had not been developed inside of the country yet. Therefore it needs some research works. Purpose of this study is to design the air motor of the hand-piece for better performance. The geometry of the air-motor is based on product of NSK Company. The airflow of the air motor unit is simulated by Computational Fluid Dynamics. The performance analysis of the air motor units is investigated. ANSYS 12.0 CFX is used to analysis of the flowfield. Torque changes depends on spin calculated by the immersed solid method.

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