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1

Modeling and simulation of PE100 pipe response under transient events caused by pump failure

Bettaieb Noura, Chalghoum Issa, Sami Elaoud, Taieb Ezzeddine Hadj

Journal of Theoretical and Applied Mechanics

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2019

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Vol. 57 nr 4

1039--1054

EN

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.

2

Improved Method for Simulating Frictional Losses in Laminar Transient Liquid Pipe Flow

Urbanowicz K., Zarzycki Z., Kudźma S.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2010

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Vol. 14, No 3

175-188

EN

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.

3

Transient Cavitating Pipe Flow: Computation Models and Methods

Urbanowicz K., Zarzycki Z.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2008

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Vol. 12, No 3-4

159-172

EN

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.

4

Simutations of transient cavitating turbulent flow using unsteady frictional loss models

Urbanowicz K., Zarzycki Z.

Transactions of the Institute of Fluid-Flow Machinery

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2007

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nr 120

53-70

EN

The paper presents two key mathematical models of transient cavitating pipe flow, i.e. column separation model (CSM) and bubbly cavitation model (BCM). Both models investigated in the paper take into account unsteady frictional loss models. The equations describing the CSM and BCM models have been solved using first the method of characteristics and then the finite differences method. The results of numerical simulations have been compared with the results obtained in the experiments. Transients which took into account unsteady wall shear stress fit well the results of experiments in comparison with quasi-steady wall shear stress model.

5

Computation of transient turbulent flow of liquid in pipe using unsteady friction formula

Zarzycki Z., Kudźma S.

Transactions of the Institute of Fluid-Flow Machinery

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2005

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nr 116

27-42

EN

The paper deals with computation and simulation of transient turbulent flow of liquid in pipes. The unsteady shear stress at pipe wall is expressed as integral convolution of weighting function and mean acceleration of liquid. Finally, the unsteady flow of liquid in the pipe is described by two equations, i.e. integro-differential motion equation and continuity equation. The above equations have been solved by means of the method of characteristics using finite difference method. Additionally, calculations have been carried out using relation for quasi-steady wall shear stress. For water hammer, the computed results have been compared to the experimental ones. The comparison of computational and experimental data confirms a high accuracy of the solutions obtained from the calculations based on the presented formulae.