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Pressure gradient flows boundary condition

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Old   July 18, 2022, 03:39
Default Pressure gradient flows boundary condition
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Jigs
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Hi Team,

I am trying to simulate a problem with pressure condition at inlet and outlet. The same problem works great with fixed value at inlet velocity but doesn't converge for pressure inputs at inlet and outlet.
Let's say I am trying to simulate with pressure inlet at 1 psi and atmospheric pressure at outlet.
Used fixedValue for inlet and outlet for pressure condition. (I did divide the density with the pressure to apply pressure gradient here as input value) - Hope this part is correct. Do correct me if I am wrong.
Now what i am confused is with the velocity (U) at inlet and outlet. Should I keep zeroGradient or any other type i should be using.

Regards,
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Old   July 20, 2022, 15:28
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Pavithran R
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You can keep velocity BC as zeroGradient
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Old   July 21, 2022, 02:11
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I did try that and it isn't converging. The simulation stops after few steps throwing below error.

Code:
smoothSolver:  Solving for Ux, Initial residual = 1, Final residual = 0.0835649, No Iterations 9
smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 0.0832669, No Iterations 9
smoothSolver:  Solving for Uz, Initial residual = 1, Final residual = 0.0962039, No Iterations 6
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3  double Foam::sumProd<double>(Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4  Foam::PCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#5  Foam::GAMGSolver::solveCoarsestLevel(Foam::Field<double>&, Foam::Field<double> const&) const at ??:?
#6  Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMatrix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const at ??:?
#7  Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#8  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:?
#9  Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
#10  Foam::fvMatrix<double>::solve() in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
#11  ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
#12  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#13  ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
Floating point exception
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Old   July 21, 2022, 02:54
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even pressureInletOutletVelocity in U at inlet didn't work. same floating point exception error.
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Old   July 21, 2022, 14:30
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Check Schems in your case and try using relaxation factors. If you using tet mesh means use nNonOrthogonalCorrectors in fvSolution
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