Session MC - Micro-Fluid Dynamics IX.
MIXED session, Tuesday afternoon, November 23
Grand III, Westin Seattle
Pulsating bubble surfactometer (PBS) devices are widely used for measuring dynamic surface tension (DST) because of their simplicity and requirement for small sample amounts. In such measurements, it is assumed that hydrodynamic effects play a negligible role in the requisite balance of forces at the bubble surface. The validity of this assumption and any errors in surface tension measurement that may occur if it is violated are examined in this talk in the simplest possible situation where there is no surfactant in the system and the surface tension of the bubble-liquid interface is consequently a constant. The free boundary problem comprised of the transient shapes of the oscillating bubble and the flow outside it in the PBS chamber is analyzed by solving the three-dimensional axisymmetric Navier-Stokes equations and associated boundary and initial conditions by a rigorous finite element algorithm. The accuracy of computed predictions is verified by comparison to high-speed visualization experiments and PIV measurement of flow fields outside the bubbles.