Important examples include propellant slosh in spacecraft tanks and rockets (especially upper stages), and cargo slosh in ships and trucks transporting liquids (for example oil and gasoline).
When the fuel level fell below critical (about 3 gallons), sloshing would cause the pump to pick up a slightly aerated mixture which was sent to the fuel distributor.
His initial fluid mechanics interests included hypersonic aerodynamics, creeping flow, sloshing and channel flows and leading to flows in porous media, ship hydrodynamics and models for flow separation.
A better understanding of fluid slosh could not only decrease this uncertainty, but increase efficiency, reduce costs and allow additional payloads to be launched.