| Popis: |
Applications employing aqueous foams begin with filling a space with foam, and the liquid loss (drainage) from the foam during and after this process plays a crucial role in its effectiveness. We describe the loss of liquid from foam and the evolution of its average liquid fraction over time. The theoretical model shows a constant drainage rate during the filling process which decays exponentially after a static column is formed. Modeling the advancing foam front requires a new time scale, the fill time, which substantially affects the drainage of liquid. Significant effects are also found by varying bubble size, foam column height, and initial expansion ratio, i.e., the volume ratio of foam to liquid. Foams with low water content are generated experimentally at the bench scale, and the measured loss of liquid is found to be in good agreement with the theoretical predictions. |
