STABILITY OF INTERFACES WHICH SEPARATE COMPRESSIBLE BULK PHASES

Criteria are developed for the prediction of the stability of equilibrium of an interfacial system involving disjoint interfaces separating bulk phases some of which may be compressible. The system must be contained within a rigid enclosure with the exception that some of the bulk phases may be connected to external regions of prespecified pressures. The criteria are formulated in terms of capillary pressure-volume data for elements which are formed by partitioning the system with impermeable barriers, together with compressibility data for the bulk phases. Body forces are ignored, and either all interfaces have constant specific Helmholtz surface energies or all fluid-fluid interfaces have constant specific Helmholtz surface energies and the remaining interfaces are such as to guarantee fixed three phase contact lines at their boundaries. In order to motivate the general development, simple examples (for which the incompressible theory is well known) are worked out in detail, new results being obtained for spherical and cylindrical interfaces. A dimensionless criterion is developed which provides rapid identification of cases where compressibility matters. © 1980 by Academic Press, Inc.