• Title, Summary, Keyword: Algebraic wall model

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On Constructing an Explicit Algebraic Stress Model Without Wall-Damping Function

  • Park, Noma;Yoo, Jung-Yul
    • Journal of Mechanical Science and Technology
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    • v.16 no.11
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    • pp.1522-1539
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    • 2002
  • In the present study, an explicit algebraic stress model is shown to be the exact tensor representation of algebraic stress model by directly solving a set of algebraic equations without resort to tensor representation theory. This repeals the constraints on the Reynolds stress, which are based on the principle of material frame indifference and positive semi-definiteness. An a priori test of the explicit algebraic stress model is carried out by using the DNS database for a fully developed channel flow at Rer = 135. It is confirmed that two-point correlation function between the velocity fluctuation and the Laplacians of the pressure-gradient i s anisotropic and asymmetric in the wall-normal direction. Thus, a novel composite algebraic Reynolds stress model is proposed and applied to the channel flow calculation, which incorporates non-local effect in the algebraic framework to predict near-wall behavior correctly.

Numerical Analysis of Turbulent Flow and Heat Transfer in a Rectangular Duct with a 180° Bend Degree (직사각단면을 갖는 180°곡관내의 난류 유동및 열전달에 관한 수치해석적 연구)

  • Choi, Y.D.;Moon, C.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.6 no.4
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    • pp.325-336
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    • 1994
  • A numerical simulation of velocity and temperature fields and Nusselt number distributions is performed by using the algebraic stress model (ASM) for the velocity profiles and low Reynolds number ${\kappa}-{\varepsilon}$ model and the algebraic heat flux model(AHFM) for turbulent heat transfer in a $180^{\circ}$ bend with a constant wall heat flux. In the low Reynolds number ${\kappa}-{\varepsilon}$ model, turbulent Prandtl number is modified by considering the streamline curvature effect and the non-equilibrium effect between turbulent kinetic energy production and dissipation rate. Every heat flux term presented in the transport equation of turbulent heat flux is reduced to algebraic expressions in a way similar to algebraic stress model. Also. in the wall region, low Reynods number algebraic heat flux model(AHFM) is applied.

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LARGE EDDY SIMULATION OF TURBULENT CHANNEL FLOW USING ALGEBRAIC WALL MODEL

  • MALLIK, MUHAMMAD SAIFUL ISLAM;UDDIN, MD. ASHRAF
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.20 no.1
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    • pp.37-50
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    • 2016
  • A large eddy simulation (LES) of a turbulent channel flow is performed by using the third order low-storage Runge-Kutta method in time and second order finite difference formulation in space with staggered grid at a Reynolds number, $Re_{\tau}=590$ based on the channel half width, ${\delta}$ and wall shear velocity, $u_{\tau}$. To reduce the calculation cost of LES, algebraic wall model (AWM) is applied to approximate the near-wall region. The computation is performed in a domain of $2{\pi}{\delta}{\times}2{\delta}{\times}{\pi}{\delta}$ with $32{\times}20{\times}32$ grid points. Standard Smagorinsky model is used for subgrid-scale (SGS) modeling. Essential turbulence statistics of the flow field are computed and compared with Direct Numerical Simulation (DNS) data and LES data using no wall model. Agreements as well as discrepancies are discussed. The flow structures in the computed flow field have also been discussed and compared with LES data using no wall model.

A Study on the Development of Low Reynolds Number Second Moment Turbulence Model (저레이놀즈수 2차 모멘트 난류모형 개발에 관한 연구)

  • 김명호;최영돈;신종근
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.6
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    • pp.1596-1608
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    • 1993
  • Low Reynolds number second moment turbulence model which be applicable to the fine gird near the wall region was developed. In this model, turbulence model coefficients in the pressure strain model of the Reynolds stress equation was expressed as functions of turbulence Reynolds number $R_{t}\equivk^{2}/(\nu\varepsilon)).$ In the derivation procedure of the present low Reynolds number algebraic stress model, Laufer's near wall experimental data on Reynolds stresses were curve fitted as functions of R$_{t}$ and the resulting simultaneous equations of the model coefficients were solved by using the boundary conditions at wall and high Reynolds number limiting conditions. Predicted Reynolds stresses and dissipation rate of turbulent kinetic energy etc. in the 2 dimensional parallel, plane channel flow and pipe flow were compared with the preditions obtained by employing the Launder-Shima model, standard algebraic stress model and several experimental data. Results show that all the Reynolds stresses and dissipation rate of turbulent kinetic energy predicted by the present low Reynolds number algebraic stress model agree better with the experimental data than those predicted by other algebraic stress models.

A Low-Reynolds Number Second Moment Closure for Turbulent Heat Fluxes (저레이놀즈수 2차 모멘트 난류 열유속모형 개발에 관한 연구)

  • 신종근;최영돈;이건휘
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.3196-3207
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    • 1993
  • A second moment turbulent closure for the turbulent heat flux near a wall is developed by modification of model constants in pressure interaction term as the variables of the turbulent Reynolds number using the universal properties of turbulent heat flux near the wall. The present model shows that model constant for the wall reflection term in pressure interaction is most important in modelling of the near wall heat flux. Fully developed pipe flows with constant wall heat flux are tested to validate the proposed model. In most of calculation region, the predicted turbulent properties agree better with the experimetal data than the results from standard algebraic heat flux model which use the uniform model constants.

Numerical Analyses on Wall-Attaching Offset Jet with Algebraic Reynolds Stress Model (대수 레이놀즈 응력모델에 의한 단이 진 벽면분류에 대한 수치해석)

  • Seo, Ho-Taek;Lee, Deuck-Soo;Boo, Jung-Sook
    • Proceedings of the KSME Conference
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    • pp.579-584
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    • 2000
  • Algebraic Reynolds Stress (ARS) model is applied in order to analyze the turbulent flow of wall-attaching offset jet and to evaluate the model's predictability. The applied numerical schemes are upwind scheme and skew-upwind scheme. The numerical results show good prediction in first order calculations (i.e., reattachment length, mean velocity, pressure), while they show slight deviations in second order (i.e., kinetic energy and turbulence intensity). By comparison with the previous results using $k-{\varepsilon}$ model, ARS model predicts better than the standard $k-{\varepsilon}$ model, however, predicts slightly worse than the $k-{\varepsilon}$ model including the streamline curvature modification. Additionally this study can reconfirm that skew-upwind scheme has approximately 25% improved predictability than upwind scheme.

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Numerical Analyses on Wall-Attaching Offset Jet with Algebraic Reynolds Stress Model (대수 레이놀즈 응력모델에 의한 단이 진 벽면분류에 대한 수치해석)

  • Seo, Ho-Taek;Bu, Jeong-Suk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.12
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    • pp.1615-1624
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    • 2000
  • Algebraic Reynolds Stree (ARS) model is applied in order to analyze the turbulent flow of wall-attaching offset jet and to evaluate the predictability of model. The applied numerical schemes are the upwind scheme and the skew-upwind scheme. The numerical results show a good prediction in the first order calculations(i.e., reattachment length, mean velocity, pressure), however, slight deviations in the second order(i.e., kinetic energy and turbulence intensity). Comparing with the previous results using the k-$\varepsilon$ model, the ARS model predicts better than the standard k-$\varepsilon$ model, however, slightly worse than the k-$\varepsilon$ model including the streamline curvature modification. Additionallay this study can reconfirm that the skew-upwind scheme has approximately 25% improved predictability than the upwind scheme.

Assessment of Explicit Algebraic Stress/Heat-Flux Models for Reduction of Heat Transfer in a Vertical Pipe with Intense Heating (Explicit Algebraic Stress/Heat-Flux 모형을 이용한 벽면가열이 높은 수직관 내의 열전달 감소에 대한 수치적 해석)

  • Baek, Seong-Gu;Park, Seung-O
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.12
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    • pp.1724-1733
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    • 2003
  • This paper assesses the prediction performance of explicit algebraic stress and heat-flux models for reduction of heat transfer coefficient in a strongly-heated vertical tube. Two explicit algebraic stress models and four explicit algebraic heat-flux models are selected for assessment. Eight combinations of explicit algebraic stress and heat-flux models are used in predicting the turbulent gas flows with intense heating, which yields the significant property-variation. The results showed that the two combinations of GS-AKN and WJ-mAKN predicted the Nusselt number and the axial wall temperature variations well and that the predictions of Nusselt number with WJ-combinations spread in a wider range than those with Gs-combinations. WJ is the explicit algebraic stress model of Wallin and Johansson and GS is the model of Gatski and Speziale and that AKN is the explicit heat-flux model of Abe, Kondoh and Nagano and mAKN is the modified AKN.

Study on the Second Moment Turbulence Model in a Square Sectioned $180^{\circ}$ Bend (정사각단면을 갖는 $180^{\circ}$ 곡관내의 2차 모멘트 난류모형에 관한 연구)

  • 김명호;염성현;최영돈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1203-1217
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    • 1994
  • In the present study, in order to analyze a turbulent flow in a square sectiond 180.deg. bend, Kim's low Reynolds number second moment turbulence closure is adopted. In this model, turbulence model constants in the wall region are modified as functions of turbulent Reynolds number by use of near wall turbulent universal properties based on Laufer's experimental results of Reynolds stress distriburions. Algebraic stress model and Reynolds stress equation model are used to verify the low Reynolds number second moment closure. The application of the present low Reynolds number algebraic stress model to the prediction of a square sectioned 180.deg. bend flow gives improved velocities and Reynolds stresses profiles compared with those obtained by using the van Driest mixing length model and present low Reynolds number Reynolds stress equation model.

Evaluation of the K-Epsilon-VV-F Turbulence Model for Natural Convection in a Rectangular Cavity (직사각형 공동 내부 자연연대류 문제에 대한 k-epsilon-vv-f 난류모델의 평가)

  • Choi Seok-Ki;Kim Seong-O;Kim Eui-Kwang;Choi Hoon-Ki
    • Journal of computational fluids engineering
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    • v.7 no.4
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    • pp.8-18
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    • 2002
  • The primary objective of the present study is evaluation of the k-ε-vv-f turbulence model for prediction of natural convection in a rectangular cavity. As a comparative study, the two-layer k-ε model is also considered. Both models, with and without algebraic heat flux model, are applied to the analysis of natural convection in a rectangular cavity. The performances of turbulence models are investigated through comparison with available experimental data. The predicted results of vertical velocity component, turbulent heat fluxes, turbulent shear stress, local Nusselt number and wall shear stress are compared with experimental data. It is shown that, among the turbulence models considered in the present study, the k-ε-vv-f model with an algebraic heat flux model predicts best the vertical mean velocity and velocity fluctuation, and the inclusion of algebraic heat flux model slightly improves the accuracy of results.