Meniscus configurations and curvatures in non-axisymmetric pores of open and closed uniform cross section

Abstract

Menisci that arise in pores of uniform cross section do not always have a unique shape. Occasionally, more than one shape is stable. The main features of the different shapes that can occur in uniform tubes are described. The meniscus shapes of perfectly wetting liquids in non-axisymmetric tubes formed from two rods separated from a plate are discussed and their meniscus curvatures calculated. Predictions are made of the spontaneous transitions from one meniscus shape to another with change in tube shape. Experiments with narrow tubes constructed from two rods separated from a plate confirmed the predicted meniscus shapes, curvatures and transition points and that curvature hysteresis in perfectly wetted tubes of uniform cross section is possible. The mechanism is distinct from accepted causes of capillary pressure hysteresis such as converging-diverging pore throats, condensation processes and wettability effects.