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    Wyświetlanie 1-3 z 3
    Tytuł:
    Convolution integral in transient pipe flow
    Autorzy:
    Urbanowicz, K.
    Zarzycki, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1933952.pdf
    Data publikacji:
    2012
    Wydawca:
    Politechnika Gdańska
    Tematy:
    numerical fluid mechanics
    transient flow
    hydraulic resistance
    convolution integral
    Opis:
    This paper is devoted to the modeling of hydraulic losses during transient flow of liquids in pressure lines. Unsteady pipe wall shear stress is presented in the form of a convolution integral of liquid acceleration and a weighting function. The weighting function depends on the dimensionless time and the Reynolds number. In its first revision (Zielke W 1968 J. ASME 90 109) it had a complex and inefficient mathematical structure (featured power growth of computational time). Therefore, further work aimed at developing the so-called efficient models for correct estimation of hydraulic resistance with simultaneous linear loading of the computer's operating memory was needed. The work compared the methods of numerical solving of the convolution integral known from the literature (classic by Zielke W 1968 J. ASME 90 109 and Yardy A E and Brown J M B 2010 J. Hydratd. Eng. 136 (7) 453 and efficient by Trikha A K 1975 J. Fluids Eng. p. 97. Kagawa T et at. 1983 Trans. Jpn. Soc. Mech. Eng. 49 (447) 2638 and Schohl G A 1993 J. Fluids Eng. 115 420). The comparison highlighted the level of usefulness of the analyzed models in simulating the water hammer and revealed the demand for further research for the improvement of efficiency of the solutions.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2012, 16, 3-4; 277--291
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Transient cavitating pipe flow: Computation models and methods
    Autorzy:
    Urbanowicz, K.
    Zarzycki, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1943252.pdf
    Data publikacji:
    2008
    Wydawca:
    Politechnika Gdańska
    Tematy:
    column separation
    bubby flow
    numerical simulation
    cavitation
    transient turbulent pipe flow
    unsteady friction
    Opis:
    The paper presents four key mathematical models of a transient cavitating pipe flow, i.e. the column separation model (CSM), the gas cavitation model (CSMG), Adamkowski’s model (CSMA) and the bubbly cavitation model (BCM). All models investigated in the paper take into account unsteady frictional loss models. The equations describing all models have been solved using the method of characteristics at first and the finite differences method then. The results of numerical simulations have been compared with the results obtained in the experiments. Transients which have taken into account the unsteady wall shear stress fit well with the results of experiments in comparison with the quasi-steady wall shear stress model.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2008, 12, 3-4; 159-172
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Improved method for simulating frictional losses in laminar transient liquid pipe flow
    Autorzy:
    Urbanowicz, K.
    Zarzycki, Z.
    Kudźma, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1943217.pdf
    Data publikacji:
    2010
    Wydawca:
    Politechnika Gdańska
    Tematy:
    unsteady pipe flow
    unsteady friction
    weighting function
    Opis:
    This paper is devoted to the problem of energy dissipation and it concerns unsteady friction modeling of the liquid flow in hydraulic lines. One dimensional (1D) quasi-steady model of energy dissipation is in common use. It means that the loss of energy is estimated by the Darcy-Weisbach formulae. Such an approximation is close to reality only for slow changes of the velocity field in the pipe cross-section. In case of fast changes, like fast transients, e.g. water hammer, it fails. In this work the wall shear stress (defined as an effect of unsteady fluid friction) is presented as a sum of quasi-steady and unsteady components. The unsteady component of the wall shear stress is modeled as an convolution of the local fluid acceleration and a weighting function w(t). The weighting function, in general, makes an allowance for a relation of the historic velocity changes and the unsteady component of the wall shear stress. Primitive weighting functions have usually very complicated structures, and what is more, they make it impossible to perform an efficient simulation of dynamical runs. In this paper, a new weighting function is presented as a sum of exponential components in order to enable efficient calculation of the unsteady component wall shear stress. A few examples of the new effective method of unsteady wall shear stress simulations, in case of the water hammer, are presented. The results of the calculations are compared with experiments known in literature and satisfying results are obtained.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2010, 14, 3; 175-188
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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