Staff

For most of us the freezing of water at 0 C° seems natural and inevitable. However, it is possible that water remains fluid even at temperatures below 0 C°. If so, the water enters a supercooled,i.e. meta-stable state in which the onset of freezing can happen spontaneously due to interaction with its surroundings. The freezing does not only differ in its structure but is also significantly faster then the freezing at 0 C°. Hence, considering the interaction with a solid surface, it is more likely for the ice to stick to the surface.

This adherence of ice can cause problems for multiple technologies, e.g. wind turbines and power lines in cold regions and especially aviation. In certain heights clouds contain supercooled drops which freeze on impact onto an aircraft and build up ice agglomerates on the wing or other parts. Thereby, the efficiency of all parts creating lift is compromised. Additionally, the ice can cover sensors and cause failure or falsify signals.

Despite its evident effect on many applications the freezing of supercooled drops impacting on a surface is not yet fully understood. In order to gain insight into the physics involved, the DFG funded project SFB-TRR 75 includes subprojects investigating the freezing of supercooled drops. In the third funding period the project C3 investigates the impact of single supercooled in a parallel air flow.

The experiments take place in a custom made icing wind tunnel using high speed shadowgraphy.

Subproject C3 of the TRR 75 Droplet dynamics under extreme ambient conditions