Making pairwise side-by-side comparisons is a good way to identify differences between different designs, time steps, or operating conditions. The linked view capability of Simcenter STAR-CCM+ facilitates such comparisons. However, sometimes the differences in a variable between two different states can be too subtle to be visually identified. In such scenarios the ability to plot the contours of the difference between the variable in the two states could make visual differences more readily apparent. This article explains the steps required for the aforementioned post-processing task using a simple test case that models the steady air flow over a confined sphere:
The idea is to create a scalar scene that demonstrates the difference in pressure contours on the surface of the sphere between two different scenarios with two different (but close) mass flow rates at the inlet. To do so, we first generate a simulation history (simh) file that contains the solution for sphere surface pressure in the first sim file and load the simh file into the second sim file. Then, using data mappers, we map the imported pressure data onto the sphere surface in the second file and subtract the mapped data from the existing pressure solution and show the result in a scalar scene.
Here's the process, assuming the starting point is the converged solution in two different sim files:
1- Open the first simulation file - let's call it Case#1.sim for simplicity - and create a solution history:
Save it as Case#1.simh. Then, select the field of function of interest, in this case Pressure:
and select the appropriate area of interest for calculating the pressure difference, which in this case is the surface of the sphere:
2- Step the simulation once so that the simh file is populated with the desired data:
3- Now, open the second sim file - let's call it Case#2.sim - and load the simulation history file (Case#1.simh) generated in previous step:
You should see it showing up under solution histories and solution views folders:
4- Create a surface data mapper:
Then, select the sphere surface as the source, pressure as the scalar field function, and most importantly, Case#1 as the representation
Select the same surface as the target:
5 - Map the data:
6- Create a field function for the pressure difference and then plot it in a scalar scene:
Note that the representation of the scalar displayer in this scene is "Volume Mesh" and not "Case#1", since the data is already mapped and used in the current (Case#2) representation.