Minimum specific energy in open-channel flows: the Salas–Dominguez contribution

The specific energy concept is basic for the computation of gradually-varied flows and it is extensively discussed in modern and classical textbooks on the hydraulics of open channels. This concept is typically attributed to Bakhmeteff who developed it in his PhD thesis in Russia in 1912. A much less known fact is that the same concept was independently developed nearly at the same time by Ramón Salas Edwards and Francisco Javier Domínguez Solar. This forum paper highlights their contributions by providing little-known but important information for the history of hydraulics. While Salas Edwards developed the theoretical concept of critical depth simultaneously with Bakhmeteff, the first comprehensive experimental investigation of critical flow was undertaken by Domínguez. His experimental research is described in detail, given that it underpinned the concepts for critical-flow measuring devices.