Characterization of foam cell size and foam quality using factorial design analyses

The mean cell (bubble) diameter and foam quality for two-phase foams generated by an Oakes mixer were measured for foams having gas volume fractions from 23 to 81 percent. Factorial design analyses were used to study the effects of liquid and gas flow rates, mixing speed, and liquid (continuous) phase viscosity on the foam cell size. It was found that the mixing speed had the largest effect on the mean bubble diameter, with the diameter decreasing with increased mixing speed. Nonlinear, empirical models were developed to predict bubble diameters from known liquid and gas flow rates and mixing speeds. Finally, the mean bubble diameter was significantly lower for a foam generated from a higher viscosity liquid (100 mPa·s) than from a lower viscosity liquid (1 mPa·s).