Breach flow formula (Water Overlay): Difference between revisions
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Flow through breaches is calculated based on the [[ | Flow through breaches is calculated based on the [[Weir formula (Water Overlay)|Weir formula]], including the consideration between free flow and submerged flow situations. | ||
The weir formula is supplied with Breach width, which is always calculated with the [[ | The weir formula is supplied with Breach width, which is always calculated with the [[Breach growth formula (Water Overlay)|Breach growth formula]] before calculating the weir flow. | ||
For the entry area, the area where the water originates from, the following also applies: | For the entry area, the area where the water originates from, the following also applies: | ||
The water level used is defined by either an [[Breach_input_area_(Water_Overlay)|input area]] or the [[External water level (Water Overlay)|external water level]]. | |||
In case of an external area, the surface height used is defined by [[External surface level (Water Overlay)|external surface level]]. This height limits how far the water level can be lowered. | * The water level used is defined by either an [[Breach_input_area_(Water_Overlay)|input area]] or the [[External water level (Water Overlay)|external water level]]. | ||
In case of an input area, the average water level is determined based on the individual grid cells of the input area. | * In case of an external area, the surface height used is defined by [[External surface level (Water Overlay)|external surface level]]. This height limits how far the water level can be lowered. | ||
* In case of an input area, the average water level is determined based on the individual grid cells of the input area. | |||
Each timestep, the external water level is changed based on the amount of water flowing in or out. | Each timestep, the external water level is changed based on the amount of water flowing in or out. | ||
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* Δw = The water flow which takes place (out of the virtual external water source) | * Δw = The water flow which takes place (out of the virtual external water source) | ||
* cell = Cell size | * cell = Cell size | ||
* w<sub>e,t</sub> = The water level of the entry area at time t. | * w<sub>e,t</sub> = The [[Surface water level formula (Water Overlay)|water level]] of the entry area at time t. | ||
* w<sub>e,0</sub> = The water level of the entry area; In case of an external area: [[External water level (Water Overlay)|EXTERNAL_WATER_LEVEL]] attribute of the breach. | * w<sub>e,0</sub> = The [[Surface water level formula (Water Overlay)|water level]] of the entry area; In case of an external area: [[External water level (Water Overlay)|EXTERNAL_WATER_LEVEL]] attribute of the breach. | ||
* A<sub>e</sub> = The size of in the entry area; In case of an external area: [[External area (Water Overlay)|EXTERNAL_AREA]] attribute of the breach. | * A<sub>e</sub> = The size of in the entry area; In case of an external area: [[External area (Water Overlay)|EXTERNAL_AREA]] attribute of the breach. | ||
==Notes== | ==Notes== | ||
*The water level w<sub>e</sub> cannot become lower than the surface height s<sub>e</sub>, defined by [[External_surface_level_(Water_Overlay)|EXTERNAL_SURFACE_LEVEL]] in case of an external entry area. In case of an input area within the project, the surface height is determined per grid cell. | *The water level w<sub>e</sub> cannot become lower than the surface height s<sub>e</sub>, defined by [[External_surface_level_(Water_Overlay)|EXTERNAL_SURFACE_LEVEL]] in case of an external entry area. In case of an input area within the project, the [[terrain height (Water Overlay)|surface height]] is determined per grid cell. | ||
==See also== | ==See also== | ||
Revision as of 08:38, 14 June 2019
Flow through breaches is calculated based on the Weir formula, including the consideration between free flow and submerged flow situations.
The weir formula is supplied with Breach width, which is always calculated with the Breach growth formula before calculating the weir flow.
For the entry area, the area where the water originates from, the following also applies:
- The water level used is defined by either an input area or the external water level.
- In case of an external area, the surface height used is defined by external surface level. This height limits how far the water level can be lowered.
- In case of an input area, the average water level is determined based on the individual grid cells of the input area.
Each timestep, the external water level is changed based on the amount of water flowing in or out.
| t=0 | we,t = we,0 |
| otherwise | we,t = we,t-1 - ( (Δw * cell) / Ae ) |
Where:
- Δw = The water flow which takes place (out of the virtual external water source)
- cell = Cell size
- we,t = The water level of the entry area at time t.
- we,0 = The water level of the entry area; In case of an external area: EXTERNAL_WATER_LEVEL attribute of the breach.
- Ae = The size of in the entry area; In case of an external area: EXTERNAL_AREA attribute of the breach.
Notes
- The water level we cannot become lower than the surface height se, defined by EXTERNAL_SURFACE_LEVEL in case of an external entry area. In case of an input area within the project, the surface height is determined per grid cell.
See also