Gas-filled cavity structures and local void fraction distribution in aerated stirred vessel

The local structural function obtained by a microresistivity probe at different hydrodynamic regimes is examined. The structures, such as the vortex-clinging structure, the appearance of one and two large cavities, small 3-3 structure, large 3-3 structure, and ragged cavities were recognized by frequency transformation of the time-domain structural function. An optimized phase discrimination in signal processing was used. The distribution of the local void fraction (alpha) in a pilot-size stirred tank was experimentally investigated, because almost no such data can be found in the literature. The two-phase mixture was composed of air and water; alpha was measured at 190 nodes in the vertical half-section plane of the vessel. Relative differences smaller than 9% between integrated values of alpha and measured gas holdups agreed reasonably well under all conditions.