As part of the solution algorithm for pathways, GoldSim analyses and sorts cell nets, Aquifer pathways, Pipe pathways, External Pathways, and Network pathways in terms of the “upstream-downstream” direction of media flows. (In this respect, one can think of a cell net as another type of pathway).
Typically, you need not be concerned about this sequencing of pathways and nets. However, in some situations, you will be prompted to take action to rectify a sequencing problem. In particular, if the upstream/downstream sequencing of pathways and nets is ambiguous or can’t be explicitly determined (e.g., the network “loops”), GoldSim will issue a warning message saying that "there is a recursive loop".
The screen below shows an example of a network which cannot be unambiguously sequenced:
GoldSim would issue a warning when you tried to connect Aquifer to Cell2:
In order to create the mass flux link, it (or another link in the loop) must be created as a previous value mass flux link. A previous value mass flux link specifies that the previous timestep's value be used instead of the current timestep's value. This corrects the sequencing problem. Note, however, that as a result, a one timestep delay in the propagation of mass is created at the point that the previous value link is inserted in a pathway network.
When you create a mass flux link, you can select the link type in the dialog that is displayed when you select the pathway to link to:
Note that if you subsequently display the Influence dialog containing the link (by double-clicking on the influence), GoldSim will indicate that the link is a Previous Value link:
Note: GoldSim will not allow
you to define a diffusive mass flux link between two Cells as a Previous Value
mass flux link. Diffusive fluxes between Cells are always coupled
links.
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