Structure of Liquid Jets and Wetting Front in the Refrigerant Mixture Falling Films at Various Contact Angles

The paper presents 3D numerical modeling of spreading dynamics of R21 (mol. fraction: 0.9) and R114 refrigerant mixture film. We considered an outer flow along a round vertical cylinder at Reynolds number 104 and contact angles of 10°, 30°, 50°, 70°, and 90°. The simulation was performed in OpenFOAM software on the basis of the volume of fluid (VOF) method. Simulated results show an occurrence of the liquid jets flowing from the upper continuous falling film in the range of contact angles 30°–90°, while the liquid flow at contact angle of 10° keeps the only continuous film till the bottom boundary of the cylinder. We defined two scenarios for wetting of the cylinder sidewall at different contact angles: liquid near the contact line moves down and towards to the cylinder surface at \(\theta = 10^\circ\), 30°, and 50°, while only vertical velocity differs from zero at \(\theta = 70^\circ\) and 90°, excluding jets at \(\theta = 70^\circ\). The increase of the contact angle leads to complication of the structure of the refrigerant mixture falling films, arising of jets and redistribution of flow rate between them.