Influence of time dependent surface tension on dynamics of thin liquid film.
Authors: J. Bialecki and J.A. Holyst
SA mathematical model of the lung bubble wall has been created. The aim of our
investigations was to study the gas exchange proccess in the human respiratory system. The
model describes increase of the transport of the oxygen across a thin liquid film covered
with a moving monoatomic layer of the surface active agent ("surfactant"). Such
a phenomenon was observed earlier in the experiment where the boundary of the area covered
with surfactant was forced to oscillate what caused the increase of the oxygen transport
across the film.
During our theoretical researches we investigated the stability of a small perturbance
added to the stationary solution of the fluid equation of motion (Navier-Stokes eq.). We
show that the stationary solution of the liquid motion is unstable above some critical
value of the Reynolds number and as a result vortices can appear. The calculated value of
the critical Reynolds number is in a good agreement with the experimental result.
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