Annular capillary surfaces
Elcrat, A., T. E. Kim, et al. (2004). "Annular capillary surfaces." Archiv der Mathematik 82(5): 449-467.
The meniscus in a symmetric annular capillary tube is investigated. The contact angles on the inner and outer tube surface need not be the same. Existence and qualitative properties of solutions are obtained using an iteration similar to that used by Johnson and Perko in the case of a circular capillary tube. If the contact angles have the same sign ideas of Siegel are used to give asymptotic estimates using circular arcs as comparison curves.