CIVL 4720 Stella^®:   A Data Entry Demonstration

This is a demonstration of a method of feeding an arbitrary set of input or inflow values into a model.   It is assumed that the reader is able to re-create the model below, using “Stella^® Systems Simulation Software”.   If you need to refresh your memory on the basics of Stella, then click this link.   This information is intended for students in Dr. David Hansen’s course, CIVL 4720, Civil Engineering Computations (Part I), Department of Civil Engineering, Dalhousie University.

1. Start by creating this model:
   
   Give meaningful names to the stocks, flow controllers and converters, as shown.
   Both tanks should have initial values = 0.
   Set the equation for the converter "Flow Rule" to "Tank_1 /100".
   Select the converter "Rainfall" as the value of the flow controller "Rain Flow In".
   Select the converter "Flow Rule" as the value of the flow controller "Flow Between Tanks".

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2. Double click on the converter "Rainfall", to open its dialog box.
   
   

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3. Type time (which replaces the highlighted {Place right hand side of equation here... }),
   
   then click on the "Become Graphical Function" button (not the "OK" button).

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4. 
   In this new dialog box, adjust the time range and the number of data points to match your desired input data.

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5. For this example, we want to import the following rainfall data:
   

   Time		Rainfall
   0			0.00
   15			1.25
   30			9.75
   45			21.60
   60			30.50
   75			31.90
   90			25.85
   105			19.30
   120			13.20
   135			7.60
   150			2.40
   165			0.00

   Adjust the time range to [0, 450] and the number of data points to 31.
   The dialog box should now look like this:
   

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6. Click on the first non-zero value in the rainfall column (beside time 15).
   The "Edit Output" box becomes highlighted.
   
   Just type the new value, 1.25, and press Enter.
   The "Edit Output" box will now shift to the next value of time.
   Just keep typing each successive value of rainfall, followed by Enter.

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7. When you have entered the last non-zero value, the dialog box should look like this:
   
   Note how Stella builds up the inflow graph as each value is edited.
   Also note how Stella, by default, interpolates between consecutive values.

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8. To access later values of time, use the scroll bar at the base of the graph.
   
   Scroll back to the beginning.

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9. If you do not want Stella to interpolate between consecutive values, but to use a step-function input, then click on the graph icon
   
   and note how your graph changes.
   
   In this case, interpolation makes sense, so click the icon again to return to a continuous input graph.
   Click "OK" to close this dialog box and to return to the model.

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10. Place a graph on the model, double click to set its title and the variables to be graphed, rescale the axes appropriately, then run the model until time 450.   This should produce the following output:
    

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11. Manual entry of a large quantity of these arbitrary values can be a nuisance, especially if the values exist in another application, such as a spreadsheet.   Suppose that the values shown in step 5 above exist in a column in an Excel worksheet.   Carry out steps 1 to 5 above in Stella, then switch to your spreadsheet.

    Then select the values, as illustrated, and copy them into the clipboard (by any one of the following methods: rightclick, click on "Copy" in the pop-up menu; or click on "Edit" in the main menu bar, then on "Copy"; or press "Ctrl+Ins"; or press "Ctrl+C").

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12. Switch back to Stella and click on the header of the column into which you wish to import these data.   The entire column of values should become highlighted in reversed colours.
    
    However, of the four methods of pasting data that one could choose in Excel, only one will work here in Stella:   press "Ctrl+V".

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13. Of the two options, "Paste" should be active by default (as illustrated).   [If not, click on it.]
    Just click on the "OK" button,
    
    and all the values appear at once.
    

"Stella" is a registered trademark of High Performance Systems, Inc.
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This page was created on 2002 10 09 and last modified on 2002 10 17 by Dr. G.H. George