Impact of a Boiling Liquid*

The impact of a liquid mass onto a solid has been well-studied in fluid mechanics, but generally in the context of a liquid surrounded by a non-condensable gas, such as water in air. This may become a problem when trying to apply results to large-scale industrial impact problems dealing with cryogenic liquids, such as sloshing in LNG or LH2 carriers, where typically the liquid is in thermal equilibrium with its own vapor, i.e., it is a boiling liquid. The key question that arises is a fundamental one: Does phase change lead to crucial differences that need to be accounted for during impact of a boiling liquid? Using two small-scale and one large-scale experimental setup we show that the answer to this question is yes. We find that rapidly condensing vapor may cause liquid mass to hit surfaces harder than expected and even may cause entrapped vapor layers to violently collapse, creating pressures that can be orders of magnitude larger than the ones observed in comparable water-air experiments. Using a mixture of experiment and theoretical arguments we give quantitative estimates of when these situations may occur.