Foam Evolution and Stability at Elevated Gravity Levels

Foaming experiments in order to understand the evolution of the foam structure blown in different directions and levels of gravity have been carried out. The key elements of the experiment are the foam generator body (henceforth FG) and the controlled blowing apparatus. The FG was a polymer foam infiltrated with a suspension (distilled water, pure tenside (SDS, 0.05m%) and SiO2 nanoparticles (2m%)) Foams were blown out at 1.5, 2, 4, 6, 10 and at 15g levels in three different directions (0, 90 and 180o, measured to the direction of the gravity vector). The elevated gravity condition was implemented in a hyper-g centrifuge (ZARM Bremen). Results show that foams can be created even at high gravity levels though the foamability and foam structure alters a lot by varying gravity level and foaming direction. At higher g-levels, under fixed gas flow rate and blowing time less foam could be produced. The average cell size varied with the blowing directions but proved constant on any gravity levels. On base of the gravity direction dependent pressure curves the foaming process was interpreted in detail. It was found that the sedimentation ruled capillary clogging is the main process by causing the gravity direction dependent foaming phenomena. The unexpected observation is that the foam stability does not depend on the gravity level.