RDICKINSON TWITTER Collection for November 15, 2014






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Types of Stormwater Inlets from HEC12 and HEC22

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Note :   Types  of  Stormwater   Inlets  from  HEC12  and  HEC22 Stormwater   Inlets  consist of four main  types  ( http://onlinemanuals.txdot.gov/txdotmanuals/hyd/storm_drain_inlets.htm ) with most common shown in Figure 1. 1.    Curb opening  inlets  either at a sag or continuous on the street, 2.    Grate  Inlets  either at a sag or in combination with a Curb opening 3.    Slotted Drains in parking lots which can be simulated as curb opening  inlets  and 4.    Combination  inlets  either at a sag or continuous on the street which combine a curb opening inlet and a grate inlet for the  stormwater  runoff A sag inlet is the end of the line for the runoff because the flow and its debris load have no other place to go as described in the  HEC-22  and  HEC-12  manuals and a continuous grade inlet...
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More St Venant Equations in #SWMM5

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This blog shows the relationship between the terms dq1, dq2, dq3 and dq4 in the SWMM5 code and the St. Venant Partial Differential Equations. dq2 = Time Step * Area wtd * (Head Downstream – Head Upstream) / Link Length or dq2 = Time Step * Area wtd * (HGL) / Link Length Qnew = (Qold – dq2 + dq3 + dq4) / ( 1 + dq1) when the force main is full dq3 and dq4 are zero and Qnew = (Qold – dq2) / ( 1 + dq1) The dq4 term in dynamic.c uses the area upstream (a1) and area downstream (a2), the midpoint velocity, the sigma factor (a function of the link Froude number), the link length and the time step or dq4 = Time Step * Velocity * Velocity * (a2 – a1) / Link Length * Sigma the dq3 term in dynamic.c uses the current midpoint area (a function of the midpoint depth), the sigma factor and the midpoint velocity dq3 = 2 * Velocity * ( Amid(current iteration) – Amid (last time step) * Sigma dq1 = Time Step * RoughFactor / Rwtd^1.333 * |Velocity| The weighted area (Awtd) is used in the dq2 term of the St...
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