Fixed boundary dual liquid bridges in zero gravity

The equilibria and stability of fixed contact line dual liquid bridges are considered. The dual liquid bridges considered consist of two fixed length single bridges joined by an open channel so that both bridges are in pressure equilibrium. The system is simplified by requiring all bounds to be of equal radius, and also by neglecting gravity or other applied forces. The dual liquid bridge is found to be generally more stable than a single bridge of equal length in the fixed pressure case, but less stable in the fixed volume case. The maximum length of dual liquid bridge in the fixed pressure case is double that for a single bridge, 7.4547 times the radius. In the fixed volume case, a rupture of the stability envelope leads to ranges of boundary conditions for which there are no stable dual liquid bridges of any volume. One exception to fixed volume destabilization is the cylindrical dual bridge. The maximum length attainable for a cylinder is 8.9868 times the radius, which not coincidentally is also the secondary stability limit for a single fixed volume cylinder (beyond the classical limit of 2 pi times the radius). The results suggest that any application which pumps fluid through a series of cylindrical liquid bridges would be most favorable using a dual liquid bridge with pressure-constrained pumping. (C) 2000 American Institute of Physics. [S1070-6631(00)00304-4].