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    Wyświetlanie 1-3 z 3
    Tytuł:
    Application of the Lattice Boltzmann Method to the flow past a sphere
    Autorzy:
    Kajzer, A.
    Pozorski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/281895.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    bluff-body flow
    Lattice Boltzmann Method
    Large Eddy Simulation
    GPU computing
    Opis:
    The results of fully resolved simulations and large eddy simulations of bluff-body flows obtained by means of the Lattice Boltzmann Method (LBM) are reported. A selection of Reynolds numbers has been investigated in unsteady laminar and transient flow regimes. Computed drag coefficients of a cube have been compared with the available data for validation purposes. Then, a more detailed analysis of the flow past a sphere is presented, including also the determination of vortex shedding frequency and the resulting Strouhal numbers. Advantages and drawbacks of the chosen geometry implementation technique, so called “staircase geometry”, are discussed. For the quest of maximum computational effi- ciency, all simulations have been carried out with the use of in-house code executed on GPU.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2017, 55, 3; 1091-1099
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Attenuating and enhancing properties of the approximate deconvolution method based on higher-order explicit and compact filters
    Autorzy:
    Caban, L.
    Tyliszczak, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/38695731.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    explicit filter
    compact filter
    van Cittert deconvolution method
    signal analysis
    sub-filter scales reconstruction
    Large Eddy Simulation
    Opis:
    We analyse the accuracy of a deconvolution (inverse filtering) method in 1D and 2D periodic domains. The deconvolution is performed by applying the iterative van Cittert method using explicit and compact filters of the 2nd to 8th order. We consider cases in which an approximate inverse filter $ G_\alpha^{-1} $ formulated to deconvolve an original function from a filtered one $ ( \overline{f} = G \ast f ) $ is constructed based on: (a) $G$ the same as used to define $ \overline{f} = G \ast f $; (b) $ G $ different than the one used to define $ \overline{f} = G \ast f $. In case (a), the convergence rate of the deconvolution process is much better when compact filters are used. This is attributed to a flatter transfer function of this type of filter and thus a smaller deterioration of the input function $ \overline{f} $. Case (b) reflects a real situation in which the precise definition of a basic filter $G$ used in $ \overline{f} = G \ast f $ is unknown. We found that when $ G_\alpha^{-1} $ is formulated based on $G$ of a higher order than the one used to define $ \overline{f} $ the reconstructed function $ f^\ast = G_\alpha^{-1} \ast \overline{f} $ is suppressed compared to the original function $f$. On the other hand, the deconvolution process performed with the use of $ G_\alpha^{-1} $ defined based on $G$ of a lower order than the order of the basic filter significantly amplifies the reconstructed function $ f^\ast $. As a result, the function $ f^\ast $ contains more energy than the function $f$, especially in the range of small and high-frequency scales. This effect is particularly strong when explicit filters of different orders are used. The impact of the filter type in the practical application of deconvolution is demonstrated based on large eddy simulations (LES) of a 2D decaying homogenous turbulent flow. LES combined with an approximate deconvolution method (ADM) for the computation of sub-filter terms shows better accuracy than in the case when these terms are modelled using the classical Smagorinsky model or when they are neglected (no-model approach). This analysis consists of comparisons of the evolution of total energy, energy spectra, and higher-order moments (variance, skewness, kurtosis) of the velocity components and vorticity. We found that more accurate results are obtained when the deconvolution is performed using the explicit filters even if the deconvolution process based on the compact filters was found to converge faster in 1D and 2D test cases. Most likely this is because in the performed LES the explicit filters correspond better to an unknown filter induced by discretisation.
    Źródło:
    Archives of Mechanics; 2023, 75, 1-2; 107-149
    0373-2029
    Pojawia się w:
    Archives of Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Large Eddy Simulation of turbulent flowand heat transfer in a Kenics static mixer
    Autorzy:
    Murasiewicz, Halina
    Zakrzewska, Barbara
    Powiązania:
    https://bibliotekanauki.pl/articles/185383.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    heat transfer
    turbulent flow
    Large Eddy Simulation
    CFD
    static mixer
    wymiana ciepła
    przepływ turbulentny
    Symulacja dużych wirów
    mikser
    Opis:
    CFD modelling of momentum and heat transfer using the Large Eddy Simulation (LES) approach hasbeen presented for a Kenics static mixer. The simulations were performed with the commercial codeANSYS Fluent 15 for turbulent flow of three values of Reynoldsnumber,Re=5 000, 10 000 and18 000. The numerical modelling began in the RANS model, where standardk−εturbulence modeland wall functions were used. Then the LES iterations started from the initial velocity and temperaturefields obtained in RANS. In LES, the Smagorinsky–Lilly modelwas used for the sub-grid scalefluctuations along with wall functions for prediction of flowand heat transfer in the near-wall region.The performed numerical study in a Kenics static mixer resulted in highly fluctuating fields of bothvelocity and temperature. Simulation results were presented and analysed in the form of velocity andtemperature contours. In addition, the surface-averaged heat transfer coefficient values for the wholeinsert length were computed and compared with the literature experimental data. Good compliance ofthe LES simulation results with the experimental correlation was obtained.
    Źródło:
    Chemical and Process Engineering; 2019, 40, 1; 87--99
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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