Foam rupture under combined action of gravity and centrifugal force

The effect of additional centrifugal force on stability and volume of the f oam formed was studied. Foamability of butanol-1 solutions was studied usin g the combined pneumatic-mechanical method in which foam was formed by air supplied through the sintered glass and simultaneous action of the mixer ro tations. The effect of centrifugal force on the time of rupture of the foam column was determined from measurements of its lifetime either when (i) bo th the gas supply and mixer rotations were switched off, or (ii) only the g as supply was switched off (the mixer rotated all the time). It was found t hat in the presence of mixer rotations the time of rupture was always signi ficantly higher, and varied with the velocity of mixer rotations. Longer li fetimes of foam columns in the presence of mixer rotations indicate that th e gravitational drainage was slowed down by the centrifugal force exerted b y the mixer on foam, and acting in a direction perpendicular to the gravity . A simple model taking into account the influence of additional centrifuga l force on gravitational syneresis was elaborated. Model predictions statin g that in the presence of centrifugal force the time of drainage should be longer and should depend on angular velocity of the mixer rotation are in a good agreement with the experimental data obtained.