The "surge equation" refers to a mathematical formula that predicts the behavior of fluid flow in a pipeline during sudden changes in flow rate. Synonyms for this term include "water hammer equation", "transient flow equation", and "pressure wave equation". These terms all describe the same phenomenon, but emphasize different aspects of the mathematical model. Additional related terms include "hydraulic shock", "pipeline surge", and "fluid transient". Understanding the surge equation is important for engineers designing pipelines and water distribution systems, as sudden changes in flow rate can cause damage to equipment or even catastrophic failure.