The hydraulic diameter, DH, is a commonly used term when handling flow in non-circular tubes and channels. Using this term, one can calculate many things in the same way as for a round tube. It is defined as
where A is the cross-sectional area, and P is the wetted perimeter of the cross-section.
表示，是一个处理非圆形管道内流动时的常用物理量，使用这一物理量可以使非圆形管道中的计算转化成圆形管道中的计算，便于求出雷诺数等数据。