FLO2D Details Hydraulic Structures

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FLO-2D Details Hydraulic Structures

• Jim O'Brien
• FLO-2D Software, Inc.

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Hydraulic Structures

• Hydraulic structures share discharge between two
  channel or floodplain elements or between
  floodplain and channel.
• Hydraulic structure can be a bridge, culvert,
  weir, spillway, etc.
• Hydraulic structures elements do not have to be
  contiguous.

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Hydraulic Structures (cont.)

• A discharge rating curve or table as a function
  of the headwater depth to calculate discharge
  Q a depth b
• More than one relationship can be used to
  simulate blockage, inlet or outlet control, etc.

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Simulate plugging and overtopping of bridges
Specify more than one discharge relationship...
d2
d1
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Hydraulic Structures

• If rating curve or table estimates outflow
  discharge that is less than inflow backwater
  effects. This reduces water surface slope and
  can effect upstream elements.
• A discharge rating table is interpolated between
  two depth increments as is more accurate than a
  rating curve.
• A negative water surface slope can result in flow
  upstream through the hydraulic structure

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Hydraulic Structures

• Line 1 is the most important
• STRUCHAR S, STRUCTNAME, IFPORCHAN(I),
  ICURVTABLE(I), INFLONOD(I), OUTFLONOD(I),
  INOUTCONT(I), HEADREFEL(I), CLENGTH(I),
  CDIAMETER(I)
• Inflow and outflow nodes, tailwater
  consideration, headwater reference elevation, and
  long culvert control
• Lines 2 and 3 are rating curve parameters and
  Line 4 is the rating table pairs

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Hydraulic Structures
S Patagonia 1 0 1713 1827 0 4425.23 0.
0. C 20. 3.543 0.890 S Mayberry 1 1
1856 1945 0 4421.18 0. 0. T 0. 0. T 5. 250
. T 8.5 500. T 10. 1000. T 12.5 1500. T 15.0 25
00. T 17.0 3000. S Keitzer 0 0 2503 2725 1
0.0 0. 0. C 5. 25.023 1.035 C
10. 30.00 1.4 R 12. 0.00
1.0
Example Projects Truckee and Rio Grande
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How Do I Make the Hydraulic Structures Rating
Table?

• Use HEC-RAS or other program
• Two cross sections upstream of bridge and two
  downstream

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Hydraulic Structures What can go wrong?

• Not too muchbut watch for severely mismatched
  depth and discharge over a range of discharge
  cause surging
• Linear Interpolation to 0.0
• Poor reference elevations
• CDIAMETER and CLENGTH

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