Influence of volume and aspect ratio of liquid bridges on capillary breakup rheometry

Capillary thinning of liquid bridges is routinely used for extensional rheology of Newtonian and complex fluids. Although it is expected that the volume and aspect ratio of a liquid bridge significantly influence its dynamics, the role played by these parameters in rheological characterization has not been previously studied. We perform numerical simulations of Newtonian as well as viscoelastic liquid bridges with the one-dimensional slender-filament approximation of Eggers and Dupont ["Drop formation in a one-dimensional approximation of the Navier-Stokes equation," J. Fluid Mech. 262, 205-221 (1994)] and Ardekani et al. ["Dynamics of bead formation, filament thinning and breakup in weakly viscoelastic jets," J. Fluid Mech. 665, 46-56 (2010)]. Sample volume and bridge aspect ratio control two phenomena that can adversely impact rheological characterization: the tendency to form satellite drops at the necking plane and the slowing down of capillary thinning due to the proximity (in parameter space) of the liquid-bridge stability boundary. The optimal range of these parameter values to avoid drop formation and slowdown is discussed.