关于热力学、热量传递和质量传递,以及流体工程的 A-Z 指南
中文 English Русский Português Español Français Deutsch 关于我们 编辑 联系我们 访问 Begell House
View in Semantic Map View in A-Z Index

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.

浏览次数: 56748 创建日期: 2 February 2011 最后修改日期: 16 March 2011 © Copyright 2010-3921 返回顶部
A-Z 索引 作者/编辑 语义地图 视觉画廊 贡献 Guest