Research Papers: Multiphase Flows

Pressure Loss in a Horizontal Two-Phase Slug Flow

[+] Author and Article Information
A. R. Kabiri-Samani1

Department of Civil Engineering, Isfahan University of Technology, P.O. Box 84156, Isfahan, Iranakabiri@cc.iut.ac.ir

S. M. Borghei

Department of Civil Engineering, Sharif University of Technology, P.O. Box 11365-9313, Azadi Avenue, Tehran, Iranmahmood@sharif.edu


Corresponding author.

J. Fluids Eng 132(7), 071304 (Jul 22, 2010) (8 pages) doi:10.1115/1.4001969 History: Received January 24, 2009; Revised June 08, 2010; Published July 22, 2010; Online July 22, 2010

The study of air-water, two-phase flows in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions, and similar conduits is of great importance for design purposes. Air can be provided by vortices at water intakes, pumping stations, aerators, steep channels, etc. Under certain conditions, air may also be introduced into pressurized intake systems, which may form large bubbles in portions of the pipe. The bubbles may, in turn, cause an unstable slug flow, or other flow patterns, that leads to sever periodic transient pressure. In this paper, an experimental model (a circular and transparent pipeline, 90 mm in ID and 10 m in length) is used to predict pressure loss in a pipeline or tunnel involving resonance and shock waves introduced by a two-phase air-water slug flow. For this purpose, differential pressure transducers were used to measure pressure loss variations in time along the pipeline at different sections and for different air/water flow rates. The experimental results of pressure loss for different hydraulic and geometric properties indicate that Weber number (We), Froude number (Fr), and air concentration (C) are the most important parameters affecting pressure loss. Finally, relations for forecasting pressure loss in these situations are presented as a function of flow characteristics.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Some two-phase flow patterns

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Figure 2

Schematic view of the experimental setup

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Figure 3

Flow pattern map from present data compared with that Ref. 1

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Figure 4

Variation in λmix/λ0 with Reynolds number

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Figure 5

The values of λmix/λ0 versus concentration (a) for Fr≤1 and (b) for Fr>1

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Figure 6

Correlation of experimental data for different Froude numbers

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Figure 7

Variation of λmix/λ0 versus Weber number for different concentrations

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Figure 8

NRMSE values (a) for Fr≤1 and (b) for Fr>1

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Figure 9

Comparison of measured and predicted values of λmix/λ0 (a) for Fr≤1 and (b) for Fr>1

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Figure 10

Variation of λmix/λ0 with C: (a) 5 Fr/ln(We) for Fr≤1 and (b) Fr/ln(We) for Fr>1

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Figure 11

Variation of λmix/λ0 versus C for Fr=2 and We=200 using Eq. 19(29-30)

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Figure 12

Friction factors for both the pressurized two-phase flow in a pipe and the free surface aerated flow over spillway




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