Regime transitions in a laminar film flowing over a cylinder

Film flows over a cylinder have industrial applications in coating processes and heat exchangers. Previous studies on such flows have assumed that the flow from both sides of the cylinder reconnects at the bottom. This may not be true in realistic scenarios and the flow may separate before reaching the bottom, as seen on the underside of a spout due to teapot effect. We perform experiments on a cylinder of diameter 3.05cm with three sugar solutions of varying concentrations and observe four regimes. Regime I has two strands with dripping flow, Regime II has two independent falling strands of continuous streams, Regime III has re-connection of the falling film to a single strand, and Regime IV has re-connection of the two streams with an air gap aft of the cylinder. For a low viscosity solution with high inertia, the capillary forces dominate the reconnection regime. Regime IV occurs when when inertia overcomes the capillary forces to cause separation at an angle such that the two streams meet in air. As the viscosity increases, the reconnected Regime III narrows and transition to Regime IV happens at lower velocities. The regimes can be demarcated on a Reynolds Number vs product of Bond number and Weber number plot on a line of slope 2. On expanding the product of Bond number and Weber number, we get wetted perimeter as a constituent of Baudoin number and the regimes are demarcated by a modified form of Weber number.