water brake

A water brake is a type of brake that utilizes water pressure to slow or stop motion. It is particularly noted for its use in locomotives, where it admits water into the cylinders to create resistance against the pistons, aiding in descent on grades.1

More generally, brakes work by decreasing speed or stopping motion, primarily by acting on rotating mechanical elements. They absorb kinetic energy through mechanical, hydrodynamic, or electrical means. Mechanical brakes commonly use friction between rotating parts and stationary elements, dissipating energy as heat. Hydrodynamic brakes, like water brakes, use fluid friction and circulation. These fluid brakes cannot completely stop rotation but can effectively dissipate large amounts of kinetic energy, provided adequate cooling for the liquid.2