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CFD-VIEW User Tips

Using the "Extra Variable" in CFD-VIEW

In CFD-VIEW, the Extra Variable list that appears in the Attribute toolbar is used for different purposes depending on the object type. If you are interested in knowing more about this feature, please read on.

For spray visualization, the Extra Variable is used to scale the droplet size. For example, consider an evaporating spray application in a combustor. If we wish to color the spray droplet with the temperature variable and scale the size of the droplet as it gets smaller due to evaporation, the following steps should be performed.

Pick the spray object in the objects list.
Select the variable T from the color variable list. The spray droplet shows temperature variation.
From the Extra Variable list, select the variable Diameter. Clicking the Maximize icon will scale the droplet size to the largest value for the selected spray object

The above steps are shown graphically in figures 1 through 3.

Step 1

Figure 1. Spray object in the object list

Step 2

Figure 2. Color variable list with Temperature selected

Step 3

Figure 3. Extra variable list with Diameter selected

Figure 4. Spray particles colored by Temperature
and extra variable set to Size (outer surfaces are transparent)

The above procedure can be applied to any data that is displayed as points.

Another application for the extra variable is in drawing stream traces as ribbons. The stream trace determines an angle that provides information about the swirl of a flow field. The twist of the ribbon can be tied to a variable called Angle in the extra variable list, which is proportional to the swirl in the flow field, as depicted in figures 5 and 6.

Figure 5. Extra variable set to Angle to show twist in the velocity field

Figure 6. Stream trace (shown as a ribbon) through the model

If you have any questions about this feature or would like us to discuss other topics in the future, please let us know.

Regards,
ESI CFD Support Team

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