What is the difference between the different Constituent Source Types used in a Constituent analysis?
When using the Constituent analysis, you can set an element to be the source setting "Is Constituent Source?" to True. When you do this, you have additional properties available. This includes Constituent Source Types and a constituent pattern. WaterGEMS and WaterCAD use the following concentration types:
A concentration source fixes the concentration of any external inflow entering the network, such as flow from a reservoir or from a negative demand placed at a junction. Basically, whatever comes out of the source will be the value set in the properties.
A flow paced booster source adds a fixed concentration to that resulting from the mixing of all inflow to the node from other points in the network. In this case, there will be some mixing with water coming into the source from other parts of the model. This option can be most useful at a tank (which as mixing) or at a junction where there is flow in and flow out.
The mass booster is similar to the flow paced booster, however the key difference is the input. For mass booster, you enter mass rate with units of mass per time, such as mg/s. So the option you would choose (mass booster or flow paced booster) will depend on the type of data you have.
Lastly, a setpoint booster source fixes the concentration of any flow leaving the node, as long as the concentration resulting from all inflow to the node is below the setpoint. This is a variation on the "Concentration" method. This type should be used when setting the concentration for a tank.
A constituent injection can be modeled with a negative demand (inflow), a reservoir, or a tank. If the injection is variable and changes over time, a constituent pattern can be used. For a junction-based constituent injection, “Is constituent source?” should be set to “True,” a base concentration should be entered, and the respective pattern should be selected. For a tank, you would do the same thing, except no negative demand is necessary, and you’ll need to select the appropriate Tank Mixing Model.