View source for Storm-water overflows

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Branching points serve the purpose of dividing an inflow into two outflows according to a certain distribution specification. Branching points can be an intake structure in rivers for water supply or irrigation purposes,forks in a sewer system, diversions of a part of the inflow or outflow of a dam, storm-water overflows etc..<br clear="left"/>

There are three possible approaches to define the distribution specification.


==Threshold model (Option 1)==

[[Bild:Theorie_Abb47b.gif|thumb|300px|Abbildung 47b: Outflow distribution using the threshold model approach.]]

According to the threshold model the second outflow (e.g. storm-water overflow: outlet pipe) is applied only after a critical inflow Q<sub>krit</sub> has been reached, due to which the first outflow (e.g. storm-water overflow: throttle)backwater retention reaches the overflow crest. In reality a perfect distribution of the outflows after having reached the threshold value is usually not possible, therefore a selectivity can be specified for the structure to better represent real conditions. 

The selectivity is defined as: <math>\mbox{Trennschaerfe} = \frac{Q_{ab}(Q_{zu}=5 \cdot Q_{krit})}{Q_{krit}}</math>

[[Bild:Theorie_Abb47.gif|thumb|left|600px|Abbildung 47: Definition selectivity parameter in BlueM]]<br clear="all"/>

==Percentage distribution (Option 2)==

Independent of inflow a constant distribution into two outflows <sub>ab1</sub> and Q<sub>ab2</sub> according to a certain percentage ratio occurs. Here too, one has the option to influence the distribution through scaling.


==Characteristic curve (Option 3)==

A dependency between outflow Q<sub>ab1</sub> and inflow, which was derived through hydraulic calculations or operating instructions, is utilized as a polygon course. The second outflow Q<sub>ab2</sub> is calculated as the residual value of inflow - Q<sub>ab1</sub>.


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[[Kategorie:BlueM Theorie]]