Abstract
Although several models such as the Rosin-Rammler equation and the Nukiyama-Tanazawa equation have been proposed to represent size distributions of particles or droplets, there are few size distribution models for micro-bubbles. In this study, we therefore investigate the applicability of the available size distribution models to micro-bubbles generated by a pressurized dissolution method. Experiments are conducted for several liquid volumetric fluxes in the decompression nozzle. Measurements of diameters of micro-bubbles are carried out in a downstream region of the decompression nozzle and in the upper tank by using phase Doppler anemometry (PDA). The experimental results indicate that (1) the Nukiyama-Tanasawa equation well represents the size distribution of micro-bubbles generated by the pressurized dissolution method, whereas the Rosin-Rammler equation fails in the representation, (2) the size distribution of micro-bubbles can be evaluated by using the Nukiyama-Tanasawa equation without measuring individual bubble diameters, provided that the mean bubble diameter and the skewness of the bubble distribution are given, and (3) an evaluation method of visibility based on the bubble size distribution and the bubble number density is proposed, and the evaluated visibility agrees well with the visibility measured in the upper tank.
