The bottom portion of the CellNet Generator dialog is used to define zones of different properties within the Cell network:
You can add and remove zones using the Add Zone and Remove Zone buttons, respectively. Each zone is given an ID (the default is Zone1, Zone2, etc.). These Zone IDs are incorporated into the names of the Cells that will be generated, so choosing the ID carefully is worthwhile.
For each zone, you have the option to define a up to two Fluids and a single (porous) Solid from a drop-down list (which includes all the available media).
The Vol. Frac. for the Solid (the column immediately to the right of the Solid column) represents the fraction of the total Cell volume filled by the solid (porous) medium. If you have a Solid present, this will typically be 1. Hence, if you specify a Solid, and leave the Vol. Frac. empty, a value of 1 is assumed.
The Vol. Frac. for the first Fluid (the column immediately to the right of the Fluid column) represents the fraction of the remaining volume (accounting for any Solids present) that is filled with the first specified Fluid. Hence, if the Solid fills the entire volume, the Vol. Frac. for the Fluid represents that saturation fraction. If you leave the Vol. Frac. for a Fluid empty, a value of 1 is assumed.
Vx is the (Darcy) velocity for the first Fluid in the positive X-direction. Vy is the velocity in the positive Y-direction. GoldSim advective mass flux links actually require a flow rate (Q). Given a velocity, the flow rate is internally computed as V*A, where A is the cross-sectional area perpendicular to the flow direction (and determined by the geometry specifications). Hence, if a porous medium solid is specified, Vx and Vy represent Darcy velocities.
For Cylindrical geometries, Vx becomes Vz, and Vy is replaced with Qr. Qr represents the total flow in the radial direction per unit length of the Z axis. Qr must have units of Length2/Time. For example, to simulate a well with a screened length of 2.5 m and an inflow rate of 1 m3/day, Qr would be specified as -1 m3/day / 2.5 m = 0.40 m2/day (the value is negative because flow is in the negative R direction).
Vx and Vy (and Vz and Qr) can be entered as equations, and can include links. If the links cannot be found when the Cell net is generated, the Cell net will still be created, but GoldSim will subsequently display error messages after the Cells are created, reporting that some of the inputs are invalid.
You can specify the direction of flow by using a negative sign in front of the definition for Vx and Vy (and Vz and Qr). During the creation of the Cell net, the negative sign is taken to mean that the flow is in the negative X, Y, Z or R-direction. The direction is implemented, and the negative sign is then removed. For example, if you specified the following:
GoldSim would create advective mass flux links that flowed from end to beginning in the row(s) of Cells that were created in the X-direction, with a flow rate of 1m/day * the appropriate area. In this case, the “end” and “beginning” are relative to the directionality for the Cells defined when specifying the discretization. A positive flow is in the same direction as the arrow, and a negative flow is in the direction opposite to the arrow.
Note: Because the CellNet
Generator can only automatically create advective flux links to other Cells in
the net it is creating, any boundaries of a Cell net are no-flow
boundaries.
The Fluid2 column allows you to add a second Fluid to each Cell in the network. The second Fluid is assumed to fill any remaining pore space in the Cell (i.e., the first Fluid is assumed to be the wetting fluid). The Vx and Vy Darcy velocities only apply to the first Fluid (i.e., you cannot use a CellNet Generator to automatically create advective connections for both Fluids).
Note: If the Vol. Frac. for
the first Fluid is specified as the number 1 (or is left blank, which is
equivalent to specifying a Vol. Frac. of 1), the second Fluid will not be added
(since there is no remaining pore space to fill). However, if the Vol.
Frac. for the first Fluid is specified as a link or expression, the second Fluid
will be added to the Cells (even if the specified link is equal to 1, and the
second Fluid therefore would have zero volume).
If you check the Create diffusive links checkbox, GoldSim will also create diffusive links between the cells. This also enables access to the last two columns in the Zone Definition section: DFx and DFy (for cylindrical geometry, DFx represents the Z-direction and DFy represents the radial direction). These columns allow you to specify adjustment factors for diffusivities. These values (which should be dimensionless) multiply the diffusive areas between adjacent cells. This can be used to represent anisotropy in the diffusivity.
If you add a second Fluid (and the first Fluid has a Vol. Frac. less than 1), and you choose to create diffusive links, GoldSim will create diffusive links for both fluids. For example, to simulate diffusion within a partially saturated porous medium through both water and air, you would define the first Fluid as water and the second Fluid as Air, and check the Create diffusive links checkbox. This would create a Cell net with both aqueous and gaseous diffusive links.
After you have defined the zones, you must then map the zones onto each of the Cells you are creating. This is done by pressing the Map Cells… button, which displays the following dialog:
This dialog is a schematic two-dimensional plot of the cell network.
By default, all Cells are assigned to the first zone. To assign one or more Cells to a different zone, select the Cells by dragging the mouse over the Cells to select them, and then select the appropriate zone from the drop list at the top of the dialog.