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Use the correct number of nodes for boundary conditions in GridGenerator

Anna Wellmann requested to merge m.schoenherr/VirtualFluids_dev:testNodeNumberInBCs into develop

In the past, we tried two different versions for setting the number of boundary condition nodes in GridGenerator.cpp

With this merge we use this version again:

            para->getParH(level)->velocityBC.numberOfBCnodes = numberOfVelocityValues;

We used the following code for some time:

            blocks = (numberOfVelocityValues / para->getParH(level)->numberofthreads) + 1;
            para->getParH(level)->velocityBC.numberOfBCnodes = blocks * para->getParH(level)->numberofthreads;

History of this code snippet:

Why do we change this again?

Not using the exact number of nodes causes problems when calculating mean values over all boundary nodes: Multiplying by the number of blocks adds some extra nodes to numberOfBCnodes. When you do a calculation that needs the values of all boundary nodes and use numberOfBCnodes, you get incorrect results.

Tests:

We added a regression test with multiple boundary conditions in https://git.rz.tu-bs.de/irmb/VirtualFluids_dev/-/merge_requests/222. When we compared both versions of the code snippets above in the regression test, we found no differences.

To do:

Edited by Anna Wellmann

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