Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication

Three-dimensional flow pattern visualization and bubble size distributions in stationary and transient upward flashing flow

Manera, A.; Prasser, H.-M.; Lucas, D.; van der Hagen, T. H. J. J.


An experimental three-dimensional reconstruction and visualization of stationary and transient flashing flow in a vertical pipe (47 mm diameter) is presented. The measurements have been performed by means of wire-mesh sensors. This type of sensor delivers two-dimensional void fraction distributions in the pipe cross-section where it is mounted with a maximum sampling rate of 10,000 frames per second. A sampling rate of 1200 frames per second has been used in this work. Steam bubbles have been identified from the wire-mesh data and their complete three-dimensional reconstruction has been performed by taking into account the steam bubble velocity. For the estimation of the bubble velocity, two wire-mesh sensors positioned at a small axial distance from each other have been used. The velocity has been determined by cross-correlation of the two wire-mesh signals, by direct identification of the traveling time of the steam bubbles between the two sensors and by means of a drift-flux model. A comparison between the three methods of bubbles velocity measurement is reported. Stationary and time-dependent bubble size distributions have been derived. The stationary radial void-fraction profiles have been decomposed according to bubble size classes and compared with the results obtained with an equilibrium model.

Keywords: Flashing; two-phase flow; three-dimensional visualization; bubble size

  • International Journal of Multiphase Flow 32(2006), 996-1016