Simulation of Transcritical Flow in Hydraulic Structures

In hydraulic engineering, transcritical flows are often required in some applications. One example is in a Venturi channel where the occurrence of critical depth is used to estimate flow rate in the channel. In this paper, a simple numerical scheme that predicts transcritical flows in hydraulic structures is developed based on the Saint Venant Equations (SVE). The solution of this scheme is aimed to be used in real time to calibrate the model that uses a measured liquid level to estimate flow rate of the fluid in a Venturi channel. The proposed algorithm consists of a set of ordinary differential equations derived from discretizing SVE in space along the channel axis. The results based on this scheme show that the algorithm is capable of predicting flows involving transcritical conditions. Errors associated with the scheme are relatively small in locating shocks in flows with imposed downstream boundary level, and in predicting the transition within the throat of Venturi channels.