• 제목/요약/키워드: Turbulence scheme

검색결과 304건 처리시간 0.031초

상용코드를 이용한 원심펌프 임펠러 유동평가 (Flow Evaluations of Centrifugal Pump Impeller Using Commercial Code)

  • 심창열;홍순삼;강신형
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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    • pp.285-292
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    • 2000
  • Numerical calculation is applied to centrifugal pump at design condition by using commercial code STAR-CD and Tascflow, and these results are compared with experimental data at impeller outlet. Numerical analysis is also performed by changing turbulence model and discretization scheme at design condition using Tascflow. Turbulence model and discretization scheme used to Tascflow are k-$\epsilon$, k-$\omega$ turbulence model and upwind, modified linear profile scheme. W;th the same turbulence model and discretization scheme, two results of STAR-CD and Tascflow are very similar. But there is significant difference in numerical results near hub and shroud of impeller with different kinds of turbulent model and discretization scheme at design condition. And with k- $\omega$ turbulence model and modified linear profile scheme, it is showed that numerical results are very similar to experimental results of impeller outlet

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난류 모수화 방법에 따른 대기경계층 수치모의 특성에 관한 연구 (Numerical Study on Characteristics of Turbulence Scheme in Planetary Boundary Layer)

  • 전원배;이화운;이순환
    • 한국환경과학회지
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    • 제19권2호
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    • pp.137-148
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    • 2010
  • This paper investigates the characteristics of turbulence schemes. Turbulence closures are fundamental for modeling the atmospheric diffusion, transport and dispersion in the boundary layer. In particular, in non-homogeneous conditions, a proper description of turbulent transport in planetary boundary layer is fundamental aspect. This study is based on the Regional Atmospheric Modeling System (RAMS) and combines four different turbulence schemes to assess if the different schemes have a impact on simulation results of vertical profiles. Two of these schemes are Isotropc Deformation scheme (I.Def) and Anisotropic deformation scheme (A.Def) that are simple local scheme based on Smagorinsky scheme. The other two are Mellor-Yamada scheme (MY2.5) and Deardorff TKE scheme (D.TKE) that are more complex non-local schemes that include a prognostic equation for turbulence kinetic energy. The simulated potential temperature, wind speed and mixing ratio are compared against radiosonde observations from the study region. MY2.5 shows consistently reasonable vertical profile and closet to observation. D.TKE shows good results under relatively strong synoptic condition especially, mixing ratio simulation. Validation results show that all schemes consistently underestimated wind speed and mixing ratio but, potential temperature was somewhat overestimated.

Application of the Goore Scheme to Turbulence Control for Drag Reduction(I) -Improvement of the Goore Schme-

  • 이창훈;김남현;김준
    • Journal of Mechanical Science and Technology
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    • 제15권11호
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    • pp.1572-1579
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    • 2001
  • We investigate the possibility of application of the Goore Scheme to turbulence control for drag reduction. In Part I, we examine the performance of the original Goore Scheme by applying it to a si mple one-dimensional problem. For the application of the scheme to turbulence control, we extend the scheme's capability so that it can treat multi-dimensional problems and examine its validity theoretically. The convergence of the extended scheme with a dynamic memory is faster by an order of magnitude than the original scheme. In Part II, we apply the proposed scheme to reduce drag for turbulent channel flows through direct numerical simulation.

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버스형상 무딘물체의 공력특성에 관한 수치해석적 고찰 - 난류모델과 이산화법의 영향 - (A Numerical Study on the Aerodynamic Characteristics of a Bus-Like Bluff Body - Effect of Turbulence Model and Discretisation Scheme -)

  • 김민호;국종영;천인범
    • 한국자동차공학회논문집
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    • 제11권3호
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    • pp.115-123
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    • 2003
  • With the advent of high performance computers and more efficient numerical algorithms, computational fluid dynamics(CFD) has come out as a modem alternative for reducing the use of wind tunnels test in automotive engineering. However, in spite of the fact that many competent researchers have made all their talents in developing turbulence model over since the past dozen or more years, it has been an important impediment in using the CFD effectively to design machinery and to diagnose or to improve engineering problems in the industry since the turbulence model has been acting as the Achilles' tendon in aspect of the reliability even to this time. In this study, Reynolds-averaged Wavier-Stokes equations were solved to simulate an incompressible turbulent flow around a bus-like bluff body near ground plane. In order to investigate the effect of the discretisation schemes and turbulence model on the aerodynamic forces several turbulence models with five convective difference schemes are adopted. From the results of this study, it is clear that choice of turbulence model and discretisation scheme profoundly affects the computational outcome. The results also show that the adoption of RNG $k-\varepsilon$ turbulence model and nonlinear quadratic turbulence model with the second order accurate discretisation scheme predicts fairly well the aerodynamic coefficients.

관류 익형송풍기의 유동해석에 대한 난류모델 및 수치도식의 영향에 관한 연구 (A Study on the Effects of Turbulence Model and Numerical Scheme on Analysis of the Flow through Airfoil Type Tubular Fan)

  • 문정주;서성진;김광용
    • 한국유체기계학회 논문집
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    • 제6권1호
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    • pp.23-29
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    • 2003
  • Three-dimensional flow through a tubular centrifugal fan with airfoil type blades is analyzed, and the effects of turbulence model and numerical scheme on the results are investigated. Standard $k-{\epsilon}$ model and k - w model are tested as turbulence closures. The numerical schemes for convection terms, i.e., Upwind Differencing Scheme (UDS), Mass Weighted Skewed upstream differencing scheme (MWS), Linear Profile Skewed upstream differencing scheme (LPS), and Modified Linear Profile Skewed upstream differencing scheme (MLPS) are also tested, and the performances of these schemes coupled with two turbulence models are evaluated. The static pressure distributions are compared with experimental data obtained in this work, which shows that the $k-{\epsilon}$ model gives better results than the k-w model.

Application of the Goore Scheme to Turbulence Control for Drag Reduction(II)-Application to Turbulence Control-

  • 이창훈;김준
    • Journal of Mechanical Science and Technology
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    • 제15권11호
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    • pp.1580-1587
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    • 2001
  • In Part I, we extended the capability of the Goore Scheme for application to multi-dimensional problems and improved convergence performance. In this paper, we apply the improved Goore Scheme to th e control of turbulence for drag reduction. Direct numerical simulations combined with the control scheme are carried out to simulate a controlled turbulent channel flow at low Reynolds number. The wall blowing and suction is applied through the Goore algorithm using the total drag as feedback. An optimum distribution of the wall blowing and suction in terms of the wall-shear stresses in the spanwise and streamwise directions is sought. The best case reduces drag by more than 20 %.

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저레이놀즈수 난류모델을 사용한 정익-동익 상호작용 해석 (Calculation of Rotor-Stator Interactions Using a Low Reynolds Number Turbulence Model)

  • 최창호;유정열
    • 대한기계학회논문집B
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    • 제23권10호
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    • pp.1229-1239
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    • 1999
  • A computational study on unsteady compressible flows has been performed by adopting a low Reynolds number $k-{\omega}$ turbulence model in conjunction with dual time stepping scheme. An explicit four-stage Runge-Kutta scheme for the Navier-Stokes equations and an approximate factorization scheme for the $k-{\omega}$ turbulence model equations are used. Computational results obtained for blade surface pressure distributions in the process of rotor-stator interaction in a turbine stage are in good agreement with extant experimental data. The effects of the wake from the stator on the boundary-layer transition over the rotor blade surface are discussed by showing that high intensity turbulence of the stator wake induces an early transition.

난류 유동장에 대한 CFDS 기법의 수치적 연구 (Numerical study of CEDS scheme for turbulent flow)

  • 문성목;김종암;노오현;홍승규
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2002년도 학술대회지
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    • pp.23-26
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    • 2002
  • An evaluation of one algebraic and two one-equation eddy viscosity-transport turbulence closure models as implemented to the CFDS(Characteristic Flux Difference Splitting) scheme is presented for the efficient computation of the turbulent flow. Comparisons of Baldwin-Lomax model as algebraic turbulence model and Baldwin-Barth and Spalart-Allmaras model as one-equation turbulence model are presented for three test cases for 3-dimensional flow. The numerical result of the CFDS schem is examined through comparison with the experimental data.

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PISO 알고리즘에서 난류예측의 후생성과 보완에 대한 연구 (A Study on Delay and Modification in Predicting Turbulence Flow in PISG Algorithm)

  • 이재원;유홍선;강관구
    • 한국전산유체공학회지
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    • 제7권1호
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    • pp.1-9
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    • 2002
  • In this paper, a modification of PISO algorithm based on standard k-ε turbulence model was proposed. The numerical technique used in this research is finite volume method, hybrid scheme for discretizing convection term, Euler implicit scheme for discretizing time term, and non-staggered grid. The basic idea of the modification of PISO algorithm is to perform an additional corrector stage for turbulence kinetic energy and dissipation rate to correct the inconsistence of flow and turbulence. In order to validate this algorithm, simulation of flow around a square cylinder (Re=3000) was performed in two-dimensional case. The results obtained from the proposed scheme show better agreement with those from the experiment than using original PISO algorithm in coherent velocity field.

CFD를 이용한 오리피스 유량계의 차압계산 (Calculations of Pressure Difference in Orifice Flowmeter using CFD)

  • 김홍민;김광용;허재영;하영철
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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    • pp.400-403
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    • 2001
  • In this study, commercial CFD code, i.e, CFX-4.3 is used to analyze the flow field and to calculate pressure differences in an orifice flowmeter. Four numerical schemes and five turbulence models are tested. Hybrid scheme and Reynolds stress model show the best performance. Chosen scheme and turbulence model are applied to predict pressure differences through the orifice for the diameter ratios, 0.3, 0.5, and 0.7. And, the results are compared with the experimental data. The results show that the calculation error is inversely proportional to the diameter ratio, and is proportional to the mass flow rate.

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