Xpswmm/ xp storm uses an enhanced version of the EPA-SWMM Version 4 Iterative Explicit Solution to solve the gradually varied unsteady flow (St Venant) equations. This dialog contains the normalised tolerances the program uses to decide whether a conduit or junction has achieved convergence. Routing Controlīy selecting Routing Control users can control the stability of the model results and the speed of execution of the run. This coefficient is global and applies to all conduits unless a value is also entered in the special conduit dialog. The loss in velocity from this change can be modelled by using a contraction/expansion loss coefficient. The abrupt cross section shape change from one conduit to the next creates turbulence. This coefficient is global and applies to all conduits, unless a value is also entered in the special conduit dialog for that conduit. The loss is actually modelled in the conduit momentum equation since only a continuity equation is used at the junctions. This multiplier of the velocity head applies both to entrance and exit losses at a junction. The minimum orifice length in m(ft) for creating an equivalent circular or rectangular conduit for orifices. Typical values used in simulations are 0.001 to 0.005. Ycrown = Total depth of the junction, ground - invert elevation Yold = Previous iteration value of depth at the junction Ynew = Current iteration value of depth at the junction The convergence error for junction depth is given by: If the difference between successive iterations of junction depth is less than this value (SURJUN) and the number of iterations is less than the maximum allowable (ITMAX), then convergence is deemed to have occurred. This is the convergence criterion used in the continuity equation at junctions. The flow convergence is tested for all CONDUITS, WEIRS, ORIFICES, PUMPS, and OUTFALLS in the model. Conduits that appear to have small instabilities in flow or velocity can be fixed by using a smaller flow tolerance. Qold = Previous iteration value of flow in the conduit Qnew = Current iteration value of flow in the conduit The convergence error for flow is given by: If the difference in both conduit flow and cross-sectional area between successive iterations is less than this value (SURTOL) and the number of iterations is less than the maximum allowable (ITMAX), then convergence is deemed to have occurred. This is the convergence criterion used during flow iterations. The convergence criterion for this method is related to the maximum number of iterations and relative accuracy, specified in the Job Control dialog. The iterative solution technique uses an under-relaxation technique to solve the dynamic flow equation and continuity equation. The following tolerances may be used to control the simulation: The first line is common for all layers the second line is specific to the Hydraulics layer. This will be printed as the title in the output file. Time Control data are required.ĭescription for simulation run (2 lines - 80 characters maximum). The Title and Simulation control fields are optional.Read the Initial Water Surface Elevation section for details. NEW FOR 2015: Users can now set the Initial Water Surface Elevation ( configuration parameter ZREF=X) from the Hdr Job Control dialog.