Inlet formula (Water Overlay)

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Inlets are hydraulic structures can pump water in and out of the project area and are connected with a water body outside the project area.

The amount flowing in or out of inlets is calculated for the cell the inlet resides on.

Inlets:
When calculating inlets, first the capacities are calculated.

If a lower threshold Tl is defined:

Qlth = max( 0 , Tl,t - wt )

If a positive Inlet q is defined:

Qt = Δt * qt

If a capacity Qtotal is defined:

Qc = Qtotal- ΣQ0..t-1

After calculating the capacities, the actual water inflow is calculated. If any of the terms are undefined, they are not included.

Δw = max( 0 , min( Qlth , Qt , Qc ) ) / A

Outlets:
When calculating outlets, first the capacities are calculated.

If an upper threshold Tu is defined:

Quth = min( 0 , Tu - wt )

If a negative Inlet q is defined:

Qt = Δt * qt

If a capacity Qtotal is defined:

Qc = -Qtotal - ΣQ0..t-1

After calculating the capacities, the actual water ouflow is calculated.

Δw = min( 0 , max( Quth , Qt , Qc) ) / A
If any of the terms are undefined, they are not included.


After the water flow (either inflow or outflow) is computed, the capacity is updated.

Cused (new) = Cused (old) + (Δw * cell)


Where:

  • Δw = The amount of water flow which takes place.
  • Δt = Computational timestep.
  • cell = Cell size.
  • A = area of the inlet/outlet
  • Cspeed = The amount of water inflow (or outflow when negative) possible based on the inlet's INLET_Q attribute.
  • Cincap = The amount of water inflow possible based on the total capacity of the inlet.
  • Coutcap = The amount of water outflow possible based on the total capacity of the outlet.
  • Cinthres = The amount of water inflow desired based on the inlet's LOWER_THRESHOLD attribute.
  • Coutthres = The amount of water outflow desired based on the outlet's UPPER_THRESHOLD attribute.
  • WLsurface = The water level on the surface, relative to datum.
  • Ctotal = The INLET_CAPACITY attribute of the inlet.
  • IQ = The INLET_Q attribute of the inlet.
  • Tl = The LOWER_THRESHOLD attribute of the inlet.
  • Tu = The UPPER_THRESHOLD attribute of the inlet.

See also

Template:WaterOverlay nav