F. Morick et D. Woermann, MIGRATION OF AIR BUBBLES IN SILICONE OIL UNDER THE ACTION OF BUOYANCYAND THERMOCAPILLARITY, Berichte der Bunsengesellschaft fur Physikalische Chemie, 97(8), 1993, pp. 961-969
Citations number
25
Categorie Soggetti
Chemistry Physical
Journal title
Berichte der Bunsengesellschaft fur Physikalische Chemie
The buoyancy driven migration of air bubbles in dimethyl-polysiloxane
and phenylmethyl-polysiloxane under isothermal conditions is studied.
The radius of the migrating bubbles increases or decreases with time.
The changes of the radii are attributed to an exchange of gas between
the bubbles and polysiloxane. The direction of the gas transport depen
ds of the state of saturation of the liquid with air. The velocity of
migrating air bubbles as function of time in dimethyl-polysiloxane can
be described by the Rybczynski-Hadamard relation using the instantane
ous values of the velocity of migration and the instantaneous value of
the radius of the bubbles. The analysis of corresponding the data obt
ained with air bubbles migrating in phenylmethyl-polysiloxane reveal t
hat in that liquid the velocity of migration is described by the Stoke
s relation using the instantaneous values of the velocity and the radi
us of the bubbles. The bubbles behave like ''hard spheres with a time
dependent radius''. The different behavior of air bubbles in the two t
ypes of polysiloxane is attributed to structural differences between m
acromolecules forming them. The observed thermocapillary motion of air
bubbles in dimethyl-polysiloxane in the presence of buoyancy forces i
s described by the theory of Young, Goldstein, Block (J. Fluid. Mech.
6, 350 (1959)). No thermocapillary motion of air bubbles is found in p
henylmethyl-polysiloxane. This is expected from the behaviour of air b
ubbles in phenylmethyl-polysiloxane under isothermal conditions.