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Research Papers: Multiphase Flows

A New Method for Numerical Prediction of Liquid Column Separation Accompanying Hydraulic Transients in Pipelines

[+] Author and Article Information
Adam Adamkowski, Mariusz Lewandowski

Department of Hydraulic Machinery, Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Gdansk 80-231, Poland

J. Fluids Eng 131(7), 071302 (Jun 19, 2009) (11 pages) doi:10.1115/1.3153365 History: Received December 03, 2007; Revised May 12, 2009; Published June 19, 2009

This paper presents a new method for calculating pressure fluctuations in pipelines during a water hammer with liquid column separation. The method is based on the discrete-vapor-cavity model (DVCM). Such kind of models assumes that vaporous cavities are formed in each computational section of the pipeline whenever the pressure drops to the vapor pressure at a given temperature. The proposed new model (new DVCM) brings a significant improvement in the reliability of predictions compared with existing DVCMs. The calculation method based on it eliminates some disadvantages of basic methods used in practice, as shown by comparisons between calculations made for simple hydraulic system under theoretical frictionless conditions using various DVCMs. Additionally, the authors present preliminary verification of the proposed model based on experimental results. The positive results of this verification, and the advantages of the new DVCM, could lead to incorporating them into commercial codes.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

The discrete model of a pipe flow with column separation

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Figure 2

Calculated pressure changes (cross section at the valve) and cavity volumes (Vcav) referred to the volume of the whole pipeline (L⋅πD2/4) obtained using the classic DVCM—calculation results for three different pipeline slopes

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Figure 3

Calculated pressure changes (cross section at the valve) and cavity volumes (Vcav) referred to the volume of the whole pipeline (L⋅πD2/4) obtained using the single-zone DVCM—calculation results for three different pipeline slopes

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Figure 4

The liquid flow and idealized vaporous zones in simple pipeline segments equivalent to each other as regards the mass and energy conservation laws

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Figure 5

Schematic diagram of the new DVCM for general case

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Figure 6

Calculated pressure changes (cross section at the valve) and cavity volumes (Vcav) referred to the volume of the whole pipeline (L⋅πD2/4) obtained using the new DVCM—calculation results for three different pipeline slopes

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Figure 7

Layout of the test stand

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Figure 8

Pressure changes measured at the valve and at the cross section located in the middle of the pipe

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Figure 9

Comparison of measured and calculated pressure surges at the valve and in the middle of the pipeline obtained using different DVCMs and the quasisteady friction model—the test run with Reo≅30,600

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Figure 10

Comparison of measured and calculated pressure surges at the valve and in the middle of the pipeline obtained using different DVCMs and the unsteady friction model—the test run with Reo≅30,600

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