Principles of Hydraulics of Open Channels

The present chapter reports the basic principles governing open channel flows. The aim is to furnish a synthetic but comprehensive analysis of the main phenomena occurring in open channels. Nevertheless, the most important governing equations are analytically derived in order to give readers a complete and, at the same time, rigorous explanation of the flow characteristics in open channels. The chapter is sub-divided into several sections. Namely, basic definitions relative to different flow regimes are discussed and illustrated, involving practical applications. The flow characteristics, including pressure distribution and velocity distribution are also illustrated and discussed. Then the analysis focuses on the uniform flow condition, for which all the main empirical relationships are provided. The analysis of the flow energy is conducted in a rigorous but simple way, providing all the essential analytical steps to generalize the proposed derivations and to highlight the main theoretical concepts. In particular, critical flow conditions are deeply analyzed and related to both specific energy and total hydrodynamic force. An ample part of the chapter is then dedicated to the description of the water surface profile characteristics. Also in this case, the analysis is conducted starting from a rigorous analytical approach and then it is specialized to the various cases, i.e. mild bed slope and steep bed slope. Finally, hydraulic jump characteristics are illustrated and discussed, along with all the analytical steps to derive both the conjugate depth ratio and the energy dissipation.