Generalized culvert design diagram

The features of culvert flow in a basic arrangement are highlighted. Four fundamental flow types may be identified, namely critical flow, uniform flow, gated flow, and pressurized flow. A generalized design diagram is presented for the circular barrel that gives the possible transitions between various flow types. Further, the lengths of free surface flows with a central pressurized flow portion are determined as a function of the pipe Froude number. Photographs of model tests illustrate the complex flow patterns that may occur even in a simple culvert arrangement. Of particular relevance are choking conditions and features of two-phase flow in a culvert. The effects of friction coefficient, bottom slope, relative pipe length, and upstream head are detailed for free culvert outlet conditions.