Inlet formula (Water Overlay)
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.
Case 1: Inlet:
When calculating inlets, first the capacities are calculated.
If a lower threshold is defined:
If a positive inlet q Q_{t} is defined:
If a capacity Q_{total} is defined:
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( Q_{lth} , Q_{t} , Q_{c} ) ) / A
Case 2 Outlets:
When calculating outlets, first the capacities are calculated.
If an upper threshold T_{u,t} is defined:
- Q_{uth} = min( 0 , T_{u,t} - w_{t} )
If a negative inlet q Q_{t} is defined:
- Q_{t} = Δt * Q_{t}
If a capacity Q_{total} is defined:
- Q_{c} = -Q_{total} - ΣQ_{0..t-1}
After calculating the capacities, the actual water ouflow is calculated. If any of the terms are undefined, they are not included.
- Δw = min( 0 , max( Q_{uth} , Q_{t} , Q_{c}) ) / A
Where:
- w_{t} = The water level on the surface relative to datum, at time t.
- T_{l,t} = The LOWER_THRESHOLD of the inlet at time t.
- T_{u,t} = The UPPER_THRESHOLD of the inlet at time t.
- q_{t} = The INLET_Q of the inlet at time t.
- Δt = Computational timestep.
- Q_{total} = The INLET_CAPACITY of the inlet.
- Q_{0..n} = The calculated previous amounts of flow.
- Q_{lth} = The desired lower water level at the inlet's location, based on the LOWER_THRESHOLD of the inlet.
- Q_{uth} = The desired upper water level at the outlet's location, based on the outlet's UPPER_THRESHOLD of the inlet.
- Q_{t} = The amount of water inflow (or outflow when negative) possible based on the INLET_Q of the inlet and timestep Δt.
- Q_{c} = The total amount of water inflow (or outflow when negative) allowed based on the total capacity of the inlet.
- A = Size of the inlet/outlet area in m^{2}, based on the amount of cells and cell size. Current implementation only has one cell.
- Δw = The amount of water flow which takes place.
Related
The following topics are related to this formula.
- Structures
- Inlet
- Models
- Surface model