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This term is commonly used in hydraulic engineering and represents the kinetic energy of a fluid flow within a given streamtube. It has the physical dimension of length (hence the term "head"), and corresponds to an energy per unit weight. If u is the velocity and g the acceleration due to gravity, the velocity head is defined by u2/2g. If the flow within a pipe, channel, or duct is uniform over a given cross-section, this definition of the velocity head applies to the entire cross-section. However, if the flow is nonuniform, the variation in kinetic energy from one streamtube to another is accounted for by a correction factor α. In this case the velocity head appropriate to the section is:

where A is the cross-sectional area and ū is the mean velocity. In terms of a traditional energy level approach, the velocity head represents the distance between the hydraulic gradient line (defined by the static head), and the total energy line or total head line.

Nombre de vues : 57544 Article ajouté : 2 February 2011 Dernière modification de l'article : 16 March 2011 © Copyright 2010-2021 Retour en haut de page
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