Curvature suppresses the Rayleigh-Taylor instability
  The dynamics of a thin liquid film on the underside of a curved cylindrical substrate is studied. The evolution of the liquid layer is investigated as the film thickness and the radius of curvature of the substrate are varied. A dimensionless parameter (a modified Bond number) that incorporates both geometric parameters, gravity, and surface tension is identified, and allows the observations to be classified according to three different flow regimes: stable films, films with transient growth of perturbations followed by decay, and unstable films. Experiments and theory confirm that, below a critical value of the Bond number, curvature of the substrate suppresses the Rayleigh-Taylor instability. 
Philippe H. Trinh, Hyoungsoo Kim, Naima Hammoud, Peter D. Howell, S.   Jonathan Chapman and Howard A. Stone
physics.flu-dyn