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Concentration-dependent outflow

This model addresses the following problem:

You have a physical container with two substances, say water and salt.   You know the expression which governs the flow of water out of the container, and need to work out the rate at which salt flows out.  

Assuming that the salt in the outflow is at the same concentration as the salt in the container, the answer is to work out the salt concentration in the container, then use this, along with the water outflow, to calculate the rate of salt outflow.

 model diagram

Note that a single physical container is modelled using two Simile compartments.

In the template, the two substances are represented by substance1 (water) and substance2 (salt).

This template can be daisy-chained, to represent a chain of containers.  This can represent, for example, a food chain, where substance1 is biomass, and substance2 is some trace substance, e.g. DDT.   In this case, you would almost certainly want to have a separate outflow from each container, but only from the substance1 compartment, representing the loss of biomass through metabolic respiration, with the DDT being left behind.  This would result in an increase in the concentration of DDT as youmove along the food chain.