Three-dimensional numerical simulations of a thin film falling vertically down the inner surface of a rotating cylinder*

Whilst gravity driven flow down the inside and outside of a stationary vertical cylinder has been investigated in some detail (Mayo et al., 2013), the flow of thin films associated with a rotating horizontal cylinder (Pougatch and Frigaard, 2011) is rare, and flow down the inside of a vertical rotating cylinder is rarer still. In this study, we focus on the latter, where a thin liquid film flows down a concave surface which itself has an imposed velocity in the azimuthal direction. A key feature of this setup is the presence of waves inclined in the expected direction of flow. An investigation of the wave dynamics is performed using three-dimensional direct numerical simulations and a volume-of-fluid approach to treat the interface. The impact of cylinder Reynolds number on the stability of these falling, rotating films is examined. As Reynolds number increases, the centrifugal force increases, producing a stabilising effect (Iwasaki and Hasegawa, 1981). An analysis of the predicted films provide a detailed insight into the relationship between the wave dynamics and internal flow fields.