The effect of fine particles on the drainage and coarsening of foam

The effects of coal fly ash dispersed in foams on the coarsening and drainage dynamics are investigated in a free drainage experiment. The growth rate of the bubbles is not significantly changed. The rates of the fluid drainage are significantly slower when powder is present, which cannot be attributed to an increase in the fluid's viscosity associated with the dispersal of powder. Instead, the drainage process can be effectively modeled by adjusting the permeability parameters that relate the liquid fraction and drainage velocity for two-phase foams; however, the values of the adjusted parameters are considerably larger than those observed and expected for non-particulate foams indicating that new physical mechanisms are at play.