Plotting Cross-Sectional Averaged Values: Part 2 – EnSight
As mentioned in Part 1 of this blog, you reduce complex 3D flows down to cross-sectional averaged values for plotting against the distance along the flow path in either of Ansys’s dedicated post-processing tools: CFD-Post and EnSight. Part 2 of this blog will focus on the method available in EnSight.
Method 3: Query
Application: Ansys EnSight
Pro: Utilizes EnSight, which can be used for much larger models than is practical with CFD-Post
Con: Defining cross-section location can be very difficult for complex geometry
EnSight’s Query tool has a built-in feature for cycling a location over a range of values, performing a calculation as it progresses, and making a plot of that data.
The first step to use this feature is to create a location that defines the cross-section of your flow path. For simple geometry this will just be a Clip along a particular direction, but for more complicated flow paths this could involve defining a spline path for a clip to follow.
![Picture9](https://www.drd.com/wp-content/uploads/2024/01/Picture9.png)
Next, you will need to create a Variable that calculates the cross-sectional average of the quantity of interest on the clip. For transported quantities, this should be a mass-flow-weighted average. Unfortunately, EnSight does not have a direction-independent mass-flow-weighted average function, but one can be built in a few steps. First, a new variable for mass flux needs to be created.
![Picture10](https://www.drd.com/wp-content/uploads/2024/01/Picture10.png)
Then, the weighted average can be calculated on the clip using the SpaMeanWeighted predefined function and the MassFlux variable that was created in the previous step.
![Picture11](https://www.drd.com/wp-content/uploads/2024/01/Picture11.png)
To create the plot of the averaged value as the clip progresses along the flow path, create a new Query using Query > Over time/distance, set the Sample to By constant on part sweep, select the variable that was just created, Start, set the range and number of samples, and then Create query.
![Picture12](https://www.drd.com/wp-content/uploads/2024/01/Picture12.png)
Note that the plot data can be exported to a file by right-clicking on the query and choosing Data > Save CSV file.
![Picture13](https://www.drd.com/wp-content/uploads/2024/01/Picture13.png)