Media Materials (such as water, sand, clay, air) that constitute (are contained within) transport pathways. GoldSim provides two types of elements for defining media: Fluids and Solids. are added to and deleted from a Cell using the Add Medium and Delete Medium buttons.
To add a new medium:
- Press the Add Medium button to display a browser An alternative view of a GoldSim model, in which elements are displayed in a tree, and organized either hierarchically, or by type. showing all of the media (and Containers with media) in the model.
- Select the medium you wish to add to the pathway and press OK.
- GoldSim will add the medium to the list of media in the cell dialog and highlight it (in yellow). Place your cursor in the Amount column and specify (as a number or via a link or expression) the quantity of the medium in the pathway. You must specify the quantity in terms of volume for Fluids and mass for Solids.
Warning: If the quantity of a medium in a Cell is not constant (and you are running at Medium or High Precision), the concentrations are computed based on an effective amount (a weighted average over the timestep A discrete interval of time used in dynamic simulations.). This can result in errors in the computed concentrations (and hence the mass flux rates) if the quantity is changing rapidly over a timestep. As a general rule, the errors will be insignificant as long as the quantity changes by less than 10% over a timestep. If this is not the case, you should reduce the timestep to ensure that it is.
Warning: If the quantity of a medium in a Cell goes completely to zero, some mass will be left behind in the Cell (until media is added to the Cell again). Although this may actually be physically realistic in some cases (e.g., outflow due to evaporation, and hence precipitation of the mass), in other cases it is not. The magnitude of the error can be reduced by reducing the timestep as the Cell approaches being empty.
Note: A medium that has zero volume (fluids) or mass (solids) cannot have a species The chemical (or non-chemical, such as bacterial or viral) constituents that are stored and transported through an environmental system in a contaminant transport model. In GoldSim, the Species element defines all of the contaminant species being simulated (and their properties). concentration. Any mass in the Cell will either partition into other Fluids (if present) or in the absence of other Fluids into which the mass can partition, precipitate out onto any Solids present in the Cell (proportional to the mass of each Solid) even if no solubility limit is specified.
To delete an existing medium:
- Select the medium you wish to delete by clicking on it in the media list for the cell (the selected medium is highlighted in yellow).
- Press the Delete Medium button.
Note: GoldSim will warn you if you try to delete a medium that is referenced in a mass flux link An interconnnection between two transport pathways that defines the rate at which species move between the pathways. for the Cell. In this case, deleting the medium will also delete the mass flux link.