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Ave head loss in links(pipes)

i have been using SWMM 5.1 for stormwater catchment modelling. i am wondering whether f L/D  should be inputted to include head loss in pipe length as a average head loss.where f is the friction factor depending on pipe relative roughness and Reynold's number; L length of the pipe and D diameter of a pipe. so for each pipe it turns out to be different.

also i am wondering how a flap works on the pipe and headloss considered due to the flap on in the pipe.

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  • The headloss for the flap gate is not considered in SWMM 5.  A flap gage simply does not allow reversal of flow in the link.  The flow is always positive or if the link has an adverse slope the flow is always negative.

    If you use DW as the friction loss then your question about f L/D will use the Reynolds number

    Subject:  ExitOther and Entrance Loss Values in SWMM 5
    The entranceexit and other losses in SWMM 5 are computed at the upstream, downstream and midpoint of the sections of the link.  However, if the normal flow equation is used for the link during a time step then these losses are zero as the flow in the link is based solely on the upstream area and upstream hydraulic radius of the link.   If you add loss coefficients and the normal flow equation is used then you will not see any change in the flow as you modify the loss coefficients.
    • Rob,

      So is it ok to input  Kcenter=f L/D as a ave head loss coefficient for a piped link?

      Regards

      Ghan

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