A series of experiments has been carried out using the Hyper-G Centrifuge at the ZARM Institut Bremen, with the partnership of the Hungarian Space Organisation. Our aim was to make tests on a special kind of foam generator and to find out how foams can be generated under macro-gravity conditions. Using this type of foam generators it is possible to blow foam in several directions, independently from the direction of gravity. This gives the possibility to produce foams with different shapes by direct gas blowing method.

In the experiments we used a mixture of distilled water, pure tenside (SDS, 0.5m%) and SiO2 nanoparticles (2m%), creating liquid aqueous foams, in order to understand the evolution of the foam structure blown in different directions even at elevated gravity levels. We studied the effect of the direction and magnitude of gravity on the foaming phenomena. Results show that foams can be created even at high gravity levels.

Foaming experiments were made at 1.5g, 2g, 4, 6g, 10g and at 15g in three different directions (0o, 90o and 180o, measured to the direction of gravity vector).

Both the foamability and stability of the liquid foams changed significantly with the gravity level and directions. At higher gravity levels, using fixed gas flow rate and blowing time less foam could be produced. The average cell size varied with the blowing directions.

The following figures give a nice overview on what happens to the foam structure when varying the direction and magnitude of gravitational acceleration.

This diagram shows the decrease of the initial foam volume in the function of gravity level. Foam were blown in 180o in this case.

The experimental setup.