Light extinction technique for void fraction measurements in bubbly flow

 The analysis of the scattering induced by a dispersion of gas bubbles in a liquid medium on a collimated, monochromatic light beam, traversing the two-phase flow, allows for the direct measurement of the 2-D distribution of the line-average of the interfacial area density. The 2-D distribution of the line-average of the void fraction is deduced from that of the interfacial area density through an image processing algorithm. To demonstrate the technique, experiments are performed in a pool of water injected with air and illuminated with a CW argon ion laser. Since the bubble diameters range from a fraction of a millimeter to a few millimeters, the scattering processes are entirely in the Mie range. The limits of applicability of the technique and the measurement uncertainty are discussed. The results compare favorably with level-swell based measurements used as a reference. Received: 14 February 1997/Accepted: 4 February 1998