[waelitani]

I have a custom boundary condition which computes the gradient of the velocity field to compute its value. It works fine in serial run. However, it fails in parallel.

uName = this->internalField().name();
const volVectorField& U = db().lookupObject<volVectorField>(uName);
volTensorField gradU = fvc::grad(U);

When the last line is commented it runs fine. Otherwise, it gives the below error. U.size() shows the correct number of cells for the processor.

[0] From const T& Foam::UPtrList<T>:perator[](Foam::label) const [with T = Foam::fvPatchField<Foam::Vector<double> >; Foam::label = int]
[0] in file /home/user/openfoam/BuildEnv/debian-build/focal-2012.latest/scratch/src/OpenFOAM/lnInclude/UPtrListI.H at line 218.
[0]
FOAM parallel run aborting
[0]
[0] #0 Foam::error:rintStack(Foam::Ostream&)[1]
[1]
[1] --> FOAM FATAL ERROR: (openfoam-2012)
[1] Cannot dereference nullptr at index 0 in range [0,12)
[1]
[1]
[1] From const T& Foam::UPtrList<T>:perator[](Foam::label) const [with T = Foam::fvPatchField<Foam::Vector<double> >; Foam::label = int]
[1] in file /home/user/openfoam/BuildEnv/debian-build/focal-2012.latest/scratch/src/OpenFOAM/lnInclude/UPtrListI.H at line 218.
[1]
FOAM parallel run aborting
[1]
[1] #0 Foam::error:rintStack(Foam::Ostream&)[LAPTOP-U0DBOLPO:28182] 1 more process has sent help message help-mpi-api.txt / mpi-abort
[LAPTOP-U0DBOLPO:28182] Set MCA parameter "orte_base_help_aggregate" to 0 to see all help / error messages
./runThis.sh: line 5: recomposePar: command not found