Explicit Iteration Hydraulic Computation and Implicit Time Step Hydraulic Computations in SWMM 5
Explicit Iteration Hydraulic Computation and Implicit Time Step Hydraulic Computations in SWMM 5 The dynamic wave solution in SWMM 5 and InfoSWMM uses an interlocking explicit iteration in an overall time step implicit calculation of the node depths and link flows. The node depths and links flows are computed based on the last iteration values for 2 to 4 iterations. It explicitly calculates the node depths and link flows at each iteration based on the last iteration value but uses an underrelaxation or Gauss-Seidel method averaging to compute the final new iteration values. The underrelaxation method averages the last iteration value and the current iteration estimate to calculate the final iteration node depth and links flow. At each time step this is the sequence of computations: 1. The time step is based on the Courant–Friedrichs–Lewy (CFL) condition for the most restrictive link (the CFL condition is based on the link length, current depth and current velocity), 2. Link flows a...