Rivulet formation in runback ice (PURVISR_U26EMP)

Ice formation on aircraft during flight is a critical safety concern. When flying through clouds, supercooled liquid droplets hit the aircraft wings/engine intakes etc and then turn to ice. These ice shapes can then affect the lift and control of the aircraft, or subsequently break-off entering engines and causing further concern.

A number of serious accidents over many years have been determined to be due to icing. Although effective mathematical models exist, they tend to only work well for smaller droplets or fail to capture some important aspects of the ice growth. One particular problem of interest is how rivulets of water or ice can form on a wing behind where anti-icing systems are in place.

Some anti-icing systems heat the wing near the leading edge (either continually or sporadically depending on the system) to melt existing ice, or to prevent ice forming at all. The unfrozen (or melting) water layer then runs back along the wing driven by local air flow and can then freeze where the substrate is no longer heated, and the wing is unprotected. In practice, depending on local conditions, the thin water film can be seen to break into rivulets before freezing.

These rivulets have been seen experimentally but there is limited modelling to predict or understand them. As a starting point, we will consider the behaviour of air-driven thin-films with freezing and look at the stability of such flows. Further work will include examining how ice shapes grow underneath such films