Tutorial 4 - Creating expressions and parameters
Page 3 of 5
In this lesson an expression is created which calculates the contaminant concentration in different plants, and also the two parameters CF and RootFactor.
Creating CF
- Open the Blocks window.
- Select Parameter from the Type drop down list and click the
button on the title bar, or right-click the window and select Create | Parameter from the pop-up menu. - Edit the new parameter. In the Properties tab, give it the following properties:
| Name | Full Name |
|---|---|
| CF | Concentration Factor |
- Select the Values tab.
- Change dimension from “Scalar” to “Matrix”.
- Set Index-1 to “Materials”. Set Index-2 to “Plants”.
- Assign the following values to the parameter:
| Materials | Plants | Value |
|---|---|---|
| NO | Pine | 0.003 |
| SO2 | Pine | 0.12 |
| NO | Fir | 0.21 |
| SO2 | Fir | 0.013 |
| NO | Wheat | 0.06 |
| SO2 | Wheat | 0.013 |
| NO | Oats | 0.093 |
| SO2 | Oats | 0.013 |
Click Ok to close the window.
Creating RootFactor
- Select Parameter from the Type drop down list and click the button on the title bar, or right-click the window and select Create | Parameter from the pop-up menu.
- Edit the new parameter. In the Properties tab, give it the following properties:
| Name | Full Name |
|---|---|
| RootFactor | Root penetration factor |
- Select the Values tab. Change dimension from “Scalar” to “Vector”.
- Set Index-1 to “Plant types”.
- Assign the following values to the parameter:
| Plant types | Value |
|---|---|
| Tree | 0.6 |
| Grain | 0.001 |
Click Ok to close the window.
Creating the expression
- Open the Blocks window
- Click the button on the title bar, or right-click the window and select Create | Expression from the pop-up menu.
- Right-click the new expression and select Edit from the pop-up menu.
- In the Properties tab, give the expression the following properties:
| Name | Full Name | Symbol |
|---|---|---|
| Plant | Concentration in plant | APlant |
- Select the Values tab. Change dimension from “Scalar” to “Matrix”. Set Index-1 to “Materials” and Index-2 to “Plants”.
- In the Default row, enter the expression “CF * ( Upper_Soil + Lower_Soil * RootFactor )”
- Click Ok to close the window.
| Note | You might wonder why Plant has to be a matrix when the expression is the same for all indices. This is because the dimension of an object determines the dimension of the output. Also, the parameters and blocks that are used have the combined dimension of 2). |
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