Modes of a liquid film falling down a vertical cylinder at different contact angles

We present the results of a three-dimensional numerical simulation of the dynamics of a falling film of a mixture of refrigerants, $0.9$ mol fraction $\rm R21 + \rm R114$, considering the liquid flow along the outer lateral surface of a round vertical cylinder for a Reynolds number of $104$ and contact angles of $10^{\circ}{,}~30^{\circ}{,}~50^{\circ}{,}~70^{\circ}{,}$ and $90^{\circ}$. The simulation was carried out using the volume of fluid (VOF) method in the OpenFOAM software. The contact angle has a significant effect on the area of the wetted surface due to a change in the modes of liquid falling down the cylinder. The following flow modes are identified: continuous film, stable jet mode, cascade jet mode, and massive jet mode. These modes are similar to the modes of fluid flow on horizontal tubes.