2008 Volume 52 Pages 877-882
Preissmann Slot concept is one of the most extensively accepted numerical approaches in unsteady free surface pressurized flow. However Courant's stability condition has imposed this method with limitation on the size of the time step. The slot concept produces large wave celerity and a corresponding strict time step limitation with too small slot width, while inaccuracies may result with too large slot width. The equations for a surcharged flow which form the lateral model are derived incorporating the relaxation effect and compared with corresponding equations of slot model. The friction loss is evaluated in slot model by introducing the coefficient, which modifies the slot model. The pair of differential equations of Slot Model and Modified Slot Model are solved and presented in forms for direct substitution into FORTRAN programming for numerical analysis. The numerical result justifies Modified Slot Model to be more efficient for the modeling of transient flow in sewer network.
