Multiphase Science and Technology A Quarterly

ISSN for PRINT: 0276-1459

For Online Access

Best Paper Award Selection - Editorial Board Site

2002, Volume14

Issue 3

64 pages

Issue price - $140.00

F. Le Gall
ERES-Innovation Phys. Therm. 10 rue Vauquelin, 75231 Paris Cedex 05, France

S. Pascal-Ribot
CEA Cadarache DTP/STH/LTA Bat. 21913108 St Paul-lez-Durance, France

J. Leblond
ESPCI, Laboratoire de Physique et Mechanique des Milieux Heterogenes, URA C.N.R.S. 857, 10 rue Vauquelin, 75231 Paris cedex 05, France

The general objective of the present work is to contribute to the understanding of the interactions between a structure and a two-phase flow by investigating the fluctuations of the liquid mass flux, the liquid momentum flux, the pressure at the wall, and of the local void fraction in a two-phase air water mixture flowing in a vertical pipe.
The fluctuations of the mass and momentum fluxes were determined by means of nuclear magnetic resonance whereas the fluctuations of the pressure at the wall were measured by a piezo-electric transducer. In addition, measurements of the fluctuations of the local void fraction were performed with an optical probe.
The experiments were carried out in two pipe configurations: (I) a standard smooth pipe and (II) a pipe containing a series of perforated plates normal to the pipe axis. In both configurations, measurements are performed at approximately the same distance from the pipe entrance. In configuration (I) the measurements were made at the end of the pipe whereas they were made downstream from the last perforated plates in configuration (II).
The RMS amplitudes of the liquid mass flux, the liquid momentum flux, the pressure at the wall, and of the local void fraction are investigated in bubbly and churn-turbulent flows as functions of the mean void fraction. Moreover, the behavior of these fluctuations are analyzed in the frequency domain.
These analyses clearly showed that the pressure fluctuations behave quite differently from the other measured quantities. This different behavior leads us to propose new scaling parameters for the wall pressure spectra. Results corroborate the role of void fraction on the structure vibrations.

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