Comparison of Wall Treatments and Meshes in Large-Eddy Simulations of Mixing Tees

    Research output: Contribution to journalArticleScientificpeer-review

    Abstract

    Large-eddy simulations (LESs) for two different T-junctions are performed for the prediction of thermal mixing loads on piping. In particular, the effects of wall treatment and mesh on temperature and wall heat flux fluctuations are studied. Wall-resolved LES shows good agreement with an experiment having adiabatic walls, but using wall functions shows deviations in root-mean-squared (RMS) temperatures and cross-stream mean velocities. The simulations show increases in peak RMS temperatures with local mesh refinement, and hence, too-low peak values are obtained with wall functions. The highest temperature fluctuations occur locally near the T-junction requiring a dense mesh. Wall functions are unable to capture high wall heat fluxes at a sharp corner, but otherwise, the maximum RMS value is close to a wall-resolved LES. For a T-junction having a round corner, higher RMS heat flux is obtained with wall functions compared to a wall-resolved case. Wall functions show lower instantaneous heat fluxes than wall-resolved LES, but the wall functions nonetheless result in higher pipe wall temperature fluctuations due to lower frequency content.

    Original languageEnglish
    Pages (from-to)25-40
    Number of pages16
    JournalNuclear Technology
    Volume204
    Issue number1
    DOIs
    Publication statusPublished - 3 Oct 2018
    MoE publication typeA1 Journal article-refereed

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    Wall function
    T shape
    Large eddy simulation
    large eddy simulation
    mesh
    Heat flux
    Temperature
    heat flux
    Pipe
    wall temperature

    Keywords

    • Computational fluid dynamics
    • large-eddy simulation
    • turbulent mixing

    Cite this

    @article{1892fe10306140e78775a8ef65b8e59b,
    title = "Comparison of Wall Treatments and Meshes in Large-Eddy Simulations of Mixing Tees",
    abstract = "Large-eddy simulations (LESs) for two different T-junctions are performed for the prediction of thermal mixing loads on piping. In particular, the effects of wall treatment and mesh on temperature and wall heat flux fluctuations are studied. Wall-resolved LES shows good agreement with an experiment having adiabatic walls, but using wall functions shows deviations in root-mean-squared (RMS) temperatures and cross-stream mean velocities. The simulations show increases in peak RMS temperatures with local mesh refinement, and hence, too-low peak values are obtained with wall functions. The highest temperature fluctuations occur locally near the T-junction requiring a dense mesh. Wall functions are unable to capture high wall heat fluxes at a sharp corner, but otherwise, the maximum RMS value is close to a wall-resolved LES. For a T-junction having a round corner, higher RMS heat flux is obtained with wall functions compared to a wall-resolved case. Wall functions show lower instantaneous heat fluxes than wall-resolved LES, but the wall functions nonetheless result in higher pipe wall temperature fluctuations due to lower frequency content.",
    keywords = "Computational fluid dynamics, large-eddy simulation, turbulent mixing",
    author = "Antti Timperi",
    year = "2018",
    month = "10",
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    doi = "10.1080/00295450.2018.1461518",
    language = "English",
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    pages = "25--40",
    journal = "Nuclear Technology",
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    publisher = "American Nuclear Society ANS",
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    }

    Comparison of Wall Treatments and Meshes in Large-Eddy Simulations of Mixing Tees. / Timperi, Antti.

    In: Nuclear Technology, Vol. 204, No. 1, 03.10.2018, p. 25-40.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Comparison of Wall Treatments and Meshes in Large-Eddy Simulations of Mixing Tees

    AU - Timperi, Antti

    PY - 2018/10/3

    Y1 - 2018/10/3

    N2 - Large-eddy simulations (LESs) for two different T-junctions are performed for the prediction of thermal mixing loads on piping. In particular, the effects of wall treatment and mesh on temperature and wall heat flux fluctuations are studied. Wall-resolved LES shows good agreement with an experiment having adiabatic walls, but using wall functions shows deviations in root-mean-squared (RMS) temperatures and cross-stream mean velocities. The simulations show increases in peak RMS temperatures with local mesh refinement, and hence, too-low peak values are obtained with wall functions. The highest temperature fluctuations occur locally near the T-junction requiring a dense mesh. Wall functions are unable to capture high wall heat fluxes at a sharp corner, but otherwise, the maximum RMS value is close to a wall-resolved LES. For a T-junction having a round corner, higher RMS heat flux is obtained with wall functions compared to a wall-resolved case. Wall functions show lower instantaneous heat fluxes than wall-resolved LES, but the wall functions nonetheless result in higher pipe wall temperature fluctuations due to lower frequency content.

    AB - Large-eddy simulations (LESs) for two different T-junctions are performed for the prediction of thermal mixing loads on piping. In particular, the effects of wall treatment and mesh on temperature and wall heat flux fluctuations are studied. Wall-resolved LES shows good agreement with an experiment having adiabatic walls, but using wall functions shows deviations in root-mean-squared (RMS) temperatures and cross-stream mean velocities. The simulations show increases in peak RMS temperatures with local mesh refinement, and hence, too-low peak values are obtained with wall functions. The highest temperature fluctuations occur locally near the T-junction requiring a dense mesh. Wall functions are unable to capture high wall heat fluxes at a sharp corner, but otherwise, the maximum RMS value is close to a wall-resolved LES. For a T-junction having a round corner, higher RMS heat flux is obtained with wall functions compared to a wall-resolved case. Wall functions show lower instantaneous heat fluxes than wall-resolved LES, but the wall functions nonetheless result in higher pipe wall temperature fluctuations due to lower frequency content.

    KW - Computational fluid dynamics

    KW - large-eddy simulation

    KW - turbulent mixing

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