Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

English (EN)·Polski (PL)·Yкраїнський (UK)
Przejdź do strony domowej biblioteki Centralna Biblioteka Wojskowa Link otwiera się w nowym oknie Logo biblioteki Prolib Integro - strona głównaCentralna Biblioteka Wojskowa

Wyszukujesz frazę "unsteady friction" wg kryterium: Temat

  Lista filtrów
Wyrównaj
    Wyświetlanie 1-6 z 6
    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
    Tytuł:
    Modeling and simulation of PE100 pipe response under transient events caused by pump failure
    Autorzy:
    Bettaieb, Noura
    Chalghoum, Issa
    Sami, Elaoud
    Taieb, Ezzeddine Hadj
    Powiązania:
    https://bibliotekanauki.pl/articles/280849.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    water hammer
    PE100
    pump failure
    viscoelasticity
    unsteady friction
    Opis:
    In this work, the response of a PE100 pipe under transient events following pump failure is numerically investigated. The developed numerical model was based on the generalized Kelvin-Voigt model and the Vitkovsky et al. formulation. The method of characteristics (MOC) was used for numerical discretization. The relevance of an unsteady friction term in the pressure wave damping was analyzed. Pressure and circumferential stress responses indicated high rates in the pressure waves damping for the PE100 pipe. Through a parametric study, it was shown that the HDPE pipe may serve in damping and dispersing pressure waves without the need for additional protection devices.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2019, 57, 4; 1039-1054
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    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:
    Analytical expressions for effective weighting functions used during simulations of water hammer
    Autorzy:
    Urbanowicz, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/281377.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    unsteady flow
    water hammer
    convolution integral
    frequency-dependent friction
    Opis:
    For some time, work has been underway aimed at significant simplification of the modelling of hydraulic resistance occurring in the water hammer while maintaining an acceptable error. This type of resistance is modelled using a convolution integral, among others, from local acceleration of a liquid and a certain weighting function. The recently completed work shows that during efficient calculations of the convolution integral, the effective weighting function used does not have to be characterised by large convergence with a classical function (according to Zielke during laminar flow and to Vardy-Brown during turbulent flow). However, it must be a sum of at least two or three exponential expressions so that the final results of the simulation could be considered as satisfactory. In this work, it has been decided to present certain analytical formulas using which it will be possible to determine the coefficients of simplified effective weighting functions in a simple direct way.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2017, 55, 3; 1029-1040
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Capacity and friction force in slide journal bearing gap by laminar unsteady lubrication
    Autorzy:
    Krasowski, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/244043.pdf
    Data publikacji:
    2010
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    laminar unsteady lubrication
    journal bearing
    pressure
    capacity and friction forces
    Opis:
    This paper shows results of numerical solutions modifled Reynolds equations for laminar unsteady oil flow in slide Journal bearing gap. Laminar unsteady oil flow is performed during periodic and unperiodic perturbations of bearing load or is caused by the changes of gap height in time. During modelling crossbar bearing operations in combustion engines, bearing movement perturbations from engine vertical vibrations causes velocity flow perturbations of lubricating oil on the bearing race and on the bearing slider in the circumferential direction. Above perturbations occur mostly during the starting and stopping of machine. This solution example applies to isothermal bearing model with infinity length. Lubricating oil used in this model has Newtonian properties and constant dynamic viscosity. Results are presented in the dimensionless hydrodynamic pressure and tangential tension distribution diagrams. Diagrams also presents capacity and friction force change during the time ofvelocity perturbations. Received solutions were compared with the solution received by the stationary lubrication flow in the slide Journal bearing, which were made with the same parameter assumption by constant dynamie oil viscosity. Isothermal bearing model is similar to friction node model by steady-state heat load conditions. Described effect can be used as on example of modelling the bearing friction node operations in reciprocating movement during exploitation of engines and machines.
    Źródło:
    Journal of KONES; 2010, 17, 3; 231-238
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Convective heat transfer in a micropolar fluid over an unsteady stretching surface
    Autorzy:
    Prasad, K. V.
    Vaidya, H.
    Vajravelu, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/266164.pdf
    Data publikacji:
    2016
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    przepływ niestacjonarny
    wymiana ciepła
    tarcie
    metoda Keller-box
    unsteady flow
    microrotation
    heat transfer
    skin friction
    Nusselt number
    Keller-box method
    Opis:
    An unsteady boundary layer free convective flow and heat transfer of a viscous incompressible, microploar fluid over a vertical stretching sheet is investigated. The stretching velocity is assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x-axis so that the sheet is stretched, keeping the origin fixed in the micropolar fluid. The transformed highly non-linear boundary layer equations are solved numerically by an implicit finite difference scheme for the transient, state from the initial to the final steady-state. To validate the numerical method, comparisons are made with the available results in the literature for some special cases and the results are found to be in good agreement. The obtained numerical results are analyzed graphically for the velocity, the microrotation, and the temperature distribution; whereas the skin friction, the couple stress coefficient and the Nusselt number are tabulated for different values of the pertinent parameters. Results exhibit a drag reduction and an increase in the surface heat transfer rate in the micropolar fluid flow compared to the Newtonian fluid flow.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2016, 21, 2; 407-422
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

      Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies