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Abstract
Linear stability theory is used to study the stability characteristics of condensate film flow down a vertical cylinder, taking into account the surface tension and the mass transfer due to phase change at the liquid-vapor interface. The problem is simplified by using the local parallel-flow approximation. Method of perturbation is applied and leads to closed form expressions for the wave amplification rate, the wave velocity, the neutral stability curve, and the critical Reynolds number. When the lateral curvature of the cylinder is taken into account, the surface tension, just as condensation mass transfer rate behaving on the vertical plate, has a dual role in the mechanism inducing instability. Results indicate that the streamwise curvature of the perturbed flow is a stabilizing effect, and the lateral curvature, on the other hand, is a destabilizing effect. The curvature of cylinder intensifies instability of the flow in comparison with the plane flow. The flow on the inner face of a cylinder is found to be more unstable than flow of the same liquid layer on the outer face.
