• Title/Summary/Keyword: Standard K-$\varepsilon$model

Search Result 239, Processing Time 0.028 seconds

Numerical Computations of Turbulent Flow in a $90^{\circ}$ Curved Duct Using a Modified Extended $k-\varepsilon$ Turbulence Model (수정된 Extendel $k-\varepsilon$ 난류모델을 사용한 $90^{\circ}$곡관 내의 난류유동에 관한 수치해석적 연구)

  • 정수진;김태훈;조진호
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.4 no.3
    • /
    • pp.139-146
    • /
    • 1996
  • An extended $k-\varepsilon$ tuebulence model modified by considering the streamline curvature effect and standard $k-\varepsilon$ turbulence model have been applied for three dimensional analysis of turbulece flow in a $90^{\circ}$ curved duct. By comparision of the results with the experimental data, the modified extended $k-\varepsilon$ model gave closer agreement with experimental data than the results from standard $k-\varepsilon$ model owing to an extra time scale of the production rate and parameter describing effects of streamline curvature included in the dissipation rate equation.

  • PDF

DEVELOPMENT OF A MODIFIED $k-{\varepsilon}$ TURBULENCE MODEL FOR VISCO-ELASTIC FLUID AND ITS APPLICATION TO HEMODYNAMICS (점탄성 유체의 난류 해석을 위한 수정된 $k-{\varepsilon}$ 난류모델 개발 및 혈류역학에의 적용)

  • Ro, K.C.;Ryou, H.S.
    • Journal of computational fluids engineering
    • /
    • v.15 no.4
    • /
    • pp.1-8
    • /
    • 2010
  • This article describes the numerical investigation of turbulent blood flow in the stenosed artery bifurcation under periodic acceleration of the human body. Numerical analyses for turbulent blood flow were performed with different magnitude of periodic accelerations using a modified turbulence model which was considering drag reduction of non-Newtonian fluid. The blood was considered to be a non-Newtonian fluid which was based on the power-law viscosity. In order to validate the modified $k-{\varepsilon}$ model, numerical simulations were compared with the standard $k-{\varepsilon}$ model and the Malin's low Reynolds number turbulence model for power-law fluid. As results, the modified $k-{\varepsilon}$ model represents intermediate characteristics between laminar and standard $k-{\varepsilon}$ model, and the modified $k-{\varepsilon}$ model showed good agreements with Malin's verified power law model. Moreover, the computing time and computer resource of the modified $k-{\varepsilon}$ model were reduced about one third than low Reynolds number model including Malin's model.

A Prediction of the Flow Characteristics around Buildings with the Turbulent Models (난류모델에 따른 건물주위의 유동 예측)

  • Lee, Seung-Ho;Yeo, Jae-Hyun;Hur, Nahm-Keon;Choi, Chang-Koon
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2008.03b
    • /
    • pp.168-171
    • /
    • 2008
  • In the present study, turbulent flows around cubic and L-shape buildings were simulated numerically. Standard ${\kappa}$-$\varepsilon$, RNG ${\kappa}$-$\varepsilon$, LES turbulence models were adopted for the present simulation. The wind pressure coefficients from these results were compared with the available experimental data. The result of RNG ${\kappa}$-$\varepsilon$ and LES turbulent models gave better prediction than that of standard ${\kappa}$-$\varepsilon$ turbulent model which is widely used in the turbulent flow simulation.

  • PDF

Numerical simulation of flow past 2D hill and valley

  • Chung, Jaeyong;Bienkiewicz, Bogusz
    • Wind and Structures
    • /
    • v.7 no.1
    • /
    • pp.1-12
    • /
    • 2004
  • Numerical simulation of flow past two-dimensional hill and valley is presented. Application of three turbulence models - the standard and modified (Kato-Launder) $k-{\varepsilon}$ models and standard $k-{\omega}$ model - is discussed. The computational methodology is briefly described. The mean velocity and turbulence intensity profiles, obtained from numerical simulations of flow past the hill, are compared with the experimental data acquired in a boundary-layer wind tunnel at Colorado State University. The mean velocity, turbulence kinetic energy and Reynolds shear stress profiles from numerical simulations of flow past the valley are compared with published experimental data. Overall, the results of simulations employing the standard $k-{\varepsilon}$ model were found to be in a better agreement with the experimental data than those obtained using the modified $k-{\varepsilon}$ model and the $k-{\omega}$ model.

Evaluation of the Anisotropic k - ${\epsilon}$ Turbulence Model by the Numerical Analysis of Axisymmetric Swirling Turbulent Flow (축대칭 선회난류의 수치해석에 의한 비등방 k - ${\epsilon}$ 난류모델의 評價)

  • Lee, Yeon-Won
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.20 no.5
    • /
    • pp.39-44
    • /
    • 1996
  • To overcome weak poinks of the standard k-${\varepsilon}$ turbulence model when applied to complex turbulent flows, various modified models were proposed. But their effects are confined to special flow fields. They have still some problems. Recently, an anisotropic k-${\varepsilon}$ turbulence model was also proposed to solve the drawback of the standard k-${\varepsilon}$ turbulence model. This study is concentrated on the evaluation of the anisotropic k-${\varepsilon}$ turbulence model by the analysis of axisymmetric swirling turbulent flow. Results show that the anisotropic k-${\varepsilon}$ turbulence model has scarecely the fundamentally physical mechanism of predicting the swirling structure of flow.

  • PDF

Prediction of Turbulent Flows with Separation and Swirl Using the RNG K-$\varepsilon$ Turbulence Model (RNG k-$\varepsilon$ 난류모델을 이용한 유동박리 및 선회를 가지는 난류유동의 예측)

  • 김성구;오군섭;김용모;이창식
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.4 no.5
    • /
    • pp.119-129
    • /
    • 1996
  • This study is concerned with the critical evaluation of predicative capability of a k-$\varepsilon$ turbulence model using the Renormalization Group(RNG) theory. The present numerical model for solution of the Navier-Stokes System is based on the modified PISO algorithms. Computations have been performed with the RNG-based K-$\varepsilon$ model for the two-dimensional flow over a backward-facing step, a confined coaxial jet, and a swirling flow in a swirl combustor. Numerical results are compared with experimental data in terms of mean flow velocities, turbulent kinetic energy, and turbulent stresses. Numerical results clearly indicate that the RNG-based K-$\varepsilon$ turbulence model shows a significant improvement over a standard K-$\varepsilon$ model in predicting the turbulent flows with flow separation and swirl.

  • PDF

The Numerical Simulation of Flow Field and Heat Transfer around 3-D Tube Banks (3차원 튜브 뱅크 주위의 난류 유동장 및 열전달에 대한 수치 해석적 연구)

  • Park, S.K.;Kim, K.W.;Ryou, H.S.;Choi, Y.K.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.8 no.3
    • /
    • pp.375-385
    • /
    • 1996
  • Turbulent flow and heat transfer characteristics around staggered tube banks were studied using the 3-D Navier-Stokes equations and energy equation governing a steady incompressible flow, which were reformulated in a non-orthogonal coordinate system with cartesian velocity components and discretized by the finite volume method with a non-staggered variable arrangement. The predicted turbulent kinetic energy using RNG $k-{\varepsilon}$ model was lower than that of standard $k-{\varepsilon}$ model but showed same result for mean flow field quantities. The prediction of the skin friction coefficient using RNG $k-{\varepsilon}$ model showed better trend with experimental data than standard $k-{\varepsilon}$ model result. The inclined flow showed higher velocity and skin friction coefficient than transverse flow because of extra strain rate ($\frac{{\partial}w}{{\partial}y}$). Also, this was why the inclined flow showed higher local heat transfer coefficient than the transverse flow.

  • PDF

Numerical Simulation of Flow Field and Organism Concentration in a UV Disinfection Channel

  • Li, Chan;Deng, Baoqing;Kim, Chang-Nyung
    • Proceedings of the KSME Conference
    • /
    • 2008.11b
    • /
    • pp.2816-2821
    • /
    • 2008
  • This paper investigates the flow field and organism concentration in a UV disinfection channel in which vertical ultraviolet lamps are arranged in a staggered configuration. Turbulence is described by low Reynolds number ${\kappa}-{\varepsilon}$ turbulence model and standard ${\kappa}-{\varepsilon}$ turbulence model, respectively. P-1 method has been employed to solve the radiative transfer equation. The obtained incident radiation is used to compute the inactivation term in the species equation. The CFD results are in good agreement with the existing experimental data for the UV channel. For the flow field, the low-Reynolds number ${\kappa}-{\varepsilon}$ model is superior to the standard ${\kappa}-{\varepsilon}$ model. The approach velocity has a significant effect on the disinfection efficiency. The organism concentration at the outlet decreases fast to a low inlet velocity.

  • PDF

Three-Dimensional Numerical Simulation on a Circular-to-Rectangular Transition Duct (Circular-to-Rectangular Transition Duct 에서의 3차원 유동장에 관한 연구)

  • Cho Soo-Yong;Son Ho-Jae
    • 한국전산유체공학회:학술대회논문집
    • /
    • 1998.11a
    • /
    • pp.55-61
    • /
    • 1998
  • The purpose of this study is to compare the predictive behaviors of the extended $k-{\varepsilon}$ turbulence model and the standard $k-{\varepsilon}$ turbulence model. Grid dependency is tested with the H-type grid and the O-type grid. Computations have been performed for a circular-to-rectangular transition duct. Numerical results for several sections along the streamwise have been obtained to compare with experimental results. The Reynolds number is 390,000 based on the bulk velocity at the inlet. The computed axial velocity contours, transverse velocity profiles, static pressure contours, peripheral skin friction coefficient, and peripheral wall static pressure distributions have been compared with experimental results. The computed results obtained with the extended $k-{\varepsilon}$ turbulence model show better agreement with experimental results than those obtained with the standard $k-{\varepsilon}$ turbulence model. Comparing to the computed results obtained with the H-type grid and O-type grid, those with H-type grid agree well with experimental results.

  • PDF

Numerical Analysis on the Blade Tip Clearance Flow in the Axial Rotor (II) - Variation of Leakage Vortex with Tip Clearance and Attack Angle - (축류 회전차 익말단 틈새유동에 대한 수치해석(II) - 틈새변화 및 영각변화에 따른 누설와류의 변화 -)

  • Ro, Soo-Hyuk;Cho, Kang-Rae
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.23 no.9
    • /
    • pp.1106-1112
    • /
    • 1999
  • Substantial losses behind axial flow rotor are generated by the wake, various vortices in the hub region and the tip leakage vortex in the tip region. Particularly, the leakage vortex formed near blade tip is one of the main causes of the reduction of performance, generation of noise and aerodynamic vibration in downstream. In this study, the three-dimensional flow fields in an axial flow rotor were calculated with varying tip clearance under various flow rates, and the numerical results were compared with experimental ones. The numerical technique was based on SIMPLE algorithm using standard $k-{\varepsilon}$ model(WFM) and Launder & Sharma's Low Reynolds Number $k-{\varepsilon}$ model(LRN). Through calculations, the effects of tip clearance and attack angle on the 3-dimensional flow fileds behind a rotor and leakage flow/vortex were investigated. The presence of tip leakage vortex, loci of vortex center and its behavior behind the rotor for various tip clearances and attack angles was described well by calculation.