Enhancing Unsteady Flow Computations in Channel Networks Using Sub-Timing Technique

Unsteady flow computations in channel networks play a pivotal role in flood forecasting and management. For sub-critical flow conditions, the implicit Preissmann scheme is a robust method for solving Saint-Venant equations. Although channel flows are predominantly sub-critical, certain flows or channel characteristics at the extreme ends may introduce varying flow regimes and transitions within a reach. This study involves the adaptation of the iteration-based channel routing model, junction point water stage prediction and correction (JPWSPC), to address the complexities arising from flow regime changes by implementing a local partial inertia technique. The model performance is evaluated on channels with different cross-sections and varying slopes. The study further investigates the computational improvement of embedding the JPWSPC model in a sub-timing framework (JPWSPC-Sub) for a network of channels with mixed flow regimes. For an elementary network of channels with extreme flow conditions, JPWSPC-Sub improves computational efficiency significantly.