The equilibrium shape and stability of menisci formed between two touching cylinders

The equilibrium shape and stability of menisci formed at the contact line between two vertically aligned cylinders were investigated by developing a general bifurcation analysis from the classic equation of Young-Laplace. It was found that the maximum amount of liquid that can be held at the contact line is determined by the existence of a bifurcation of the equilibrium solutions. The onset of instability is characterized by a translationally symmetric bifurcation that always precedes the instability to asymmetric perturbations. The maximum stable liquid retention is a strong function of the ratio of gravitational to surface tension forces, indicating that gravity acts as a destabilizing force. The effect of contact angle on the maximum liquid retention is more complex: when the gravitational effects are small, an increase in contact angle results in a decrease in liquid retention; on the other hand, when the gravitational effects are appreciable, a maximum value of the liquid retention is obtained for intermediate values of the contact angle.