The most appropriate way to represent spatially variable properties of a Fluid (such as water) is to clone the Reference Fluid. For example, if the pH varied significantly between two locations, then the solubilities may also change significantly. To represent this, you could clone the Reference Fluid and assign it a different set of solubilities. You could then place the different clones of the Reference Fluid in different portions (Containers) of the model, as appropriate.
In order to understand how to clone the Reference Fluid (and other media elements), you must be comfortable with cloning elements and localizing Containers. Clone elements automatically mimic each other, such that if you change a property of a clone, the property is automatically changed in all of the other clones. Hence, if you clone the Reference Fluid element and change a property (such as a solubility) in one clone, it is automatically changed in all the other clones.
How, then, can you use a clone to vary a property (such as the solubility) in a different clone medium? This can be accomplished because if you enter a link ID into an input field for a clone element, the same ID will appear in the corresponding input field of all of the clone elements. If, however, different elements having that same ID exist at the locations (Containers) where the clones are, each clone will link to a different element for that particular input, allowing the value of the property to be different in each Container.
The steps required to create a cloned spatially variable fluid are outlined below:
1. Make sure that the fluid properties that you wish to be spatially variable are defined via links (i.e., an element ID).
2. Identify the pathway(s) and/or Source(s) which will utilize spatially variable media properties.
3. Localize the Containers that those pathways/Sources are located in.
4. Create a clone of the Reference Fluid in each of those localized Containers.
5. Insert elements defining the spatially variable properties in each localized Container, and link them to each local Reference Fluid clone. Note that these elements must have the same name (since they are referenced by a cloned media element), but they themselves should not be clones.
Two points should be noted when cloning the Reference Fluid:
•Unlike most other elements, when you clone the Reference Fluid, the IDs of the clones are forced to be identical. As a result, the clones must be placed in separate localized Containers.
•Unlike other fluids (in which the partition coefficient is equal to the ratio of the solubilities), the partition coefficients between cloned Reference Fluids are automatically defined by GoldSim as being equal to one.
To better understand the implications of simulating spatially variable fluid properties in this manner, it is instructive to consider a situation in which two Cells (necessarily present in two different Containers) with cloned Reference Fluids (having different solubilities) are connected by a diffusive mass flux link. If we run such a simulation long enough, the system will eventually reach a steady state. At steady state (the time at which there is no net flux between the cells), the concentration in the two Cells will be identical (since although they have different solubilities, the partition coefficient is equal to 1).
Note that this is in contrast to the situation in which two different fluids are used (rather than a cloned Reference Fluid). In that case, the Cells would actually have different concentrations at steady state (with the ratio being the partition coefficient).
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