SWMM56

Conduit   Lengthening  in  SWMM   5 If you use the  conduit   lengthening  option in  SWMM   5   then your short  conduits  will be  lengthened  based on the CFL or explicit time step criterion.  Any  conduits  in which the  Length Factor  or the  courant time step link length over the original length is greater than  1  will be  lengthened  and will have its roughness lowered so that the  conduit  is hydraulically the same at full  conduit depth.  The full area, full width and full hydraulic radius stay the same in the modified link – only the length, slope and roughness are altered. Length Factor     = (Wave Celerity + Full Depth Velocity) * Time Step /  Conduit  Length, and for those links in which the  Length Factor  is greater than  1 New Roughness =  Old Roughness / ( Length Factor ) ^1/2 New Slope ...

Conduit Lengthening in SWMM 5 If you use the conduit lengthening option in SWMM 5 then your short conduits will be lengthened based on the CFL or explicit time step criterion. Any conduits in which the Length Factor or the courant time step link length over the original length is greater than 1 will be lengthened and will have its roughness lowered so that the conduit is hydraulically the same at full conduit depth. The full area, full width and full hydraulic radius stay the same in the modified link – only the length, slope and roughness are altered. Length Factor = (Wave Celerity + Full Depth Velocity) * Time Step / Conduit Length, and for those links in which the Length Factor is greater than 1 New Roughness = Old Roughness / ( Length Factor ) ^1/2 New Slope = Old Slope / Length Factor A few metric's for showing how this option has altered the network are shown in the figure below: 1. The most important is the increase in Network full volume as you never want...