# Best way to compare two cases which should give the same results

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 April 1, 2012, 11:30 Best way to compare two cases which should give the same results #1 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 460 Rep Power: 18 Hi all; I'm testing MRFSimpleFoam on a car with rotating wheels. I found 2 ways to achieve the rotation of the wheels so I would like to check that my results are the same in both the cases. From what I can see from the pressure and velocity fields in paraview they seem the same but I would like to be certain of that in a more "mathematical" way… Can anybody please give me a suggestion on how to do that? For example it would be great to evaluate the difference in pressure between the two cases everywhere in my domain and then make sure that there numbers I'd get were close to 0 everywhere on my domain… I would like to point out the the cases have the same geometry, mesh and boundary condition. I only used topoSet instead of setSet. Thank you!

 April 1, 2012, 11:54 #2 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 460 Rep Power: 18 I think I found a way in paraview: I loaded both the geometries which were called, say, geomerty1 and geometry2. Then I applied a calculator filter to both of them and every calculator had these formulas: p1=p for geometry 1 p2=p for geometry 2 this way I could easily identify what pressure was what. At this point I selected bot the calculator-->filter-->append attributes. I then used another calculator on the appended attributes with: deltaP=p1-p2 If there a simpler way I would be glad to know of it. arashgmn likes this.

 April 1, 2012, 18:17 #3 Senior Member     Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 16 Hi Lore. From what i've seen, on rotating wheels it is customary to plot the Cp vs angle on the circumference. For the wake effect and/or turbulence quantities, plots of lines on the symmetry. This should give you some graphs to look at. But your mehod seems reasonable too. arashgmn likes this. __________________ http://www.leadingedge.it/ Naval architecture and CFD consultancy

 April 1, 2012, 18:23 #4 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 460 Rep Power: 18 Thank you Vieri! I'll try that!