Lattice Boltzmann simulations and contact angle hysteresis in convergent-divergent media

The lattice Boltzmann method was used to perform multiphase fluid dynamics calculations that include preferential fluid interactions with solid walls. Contact angle was calibrated with respect to wall interaction parameters using captive drops and observed LaPlace pressure differences across interfaces. In simulations, captive drops were forced to propagate down straight tubes to observe dynamic contact angles. Captive drops were also propagated down sinusoidally constricted capillaries in simulations to observe dynamic contact angles in convergent-divergent systems. Rate effects on observed contact angle were also probed. Negligible hysteresis or rate effect was observed over the conditions examined, indicating that the phenomenon of contact angle hysteresis is not a result of hydrodynamic interactions with an equilibrium wetting condition. It is conjectured that the time scale for solid-fluid interaction is too short in the current lattice Boltzmann scheme in comparison with that for hydrodynamic interaction. The results suggest that such lattice Boltzmann models must incorporate dynamic rock-fluid interactions different from static ones in order to portray these known phenomena or slow the mathematical equilibration process for preferential wetting. (C) 2002 Published by Elsevier Science B.V.