[ldxfx]

Dear OFers,
I am working on the subject of periodic flows in a pipe. I set the inlet boundary type "mappedPatch" and outlet "patch". It works when the gridding is excessive, but if I reduce number of gridding, errors appear as follows.
I don't know where is the mistake.Oh,really hope you can bail me out!
Thanks!

Codes:
Create time

Create mesh for time = 0

Reading field p

Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting RAS turbulence model laminar
No finite volume options present


SIMPLE: convergence criteria
field p tolerance 0.01
field U tolerance 0.001


Starting time loop

Time = 0.001

#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::sigSegv::sigHandler(int) at ??:?
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam::mapDistribute::mapDistribute(Foam::List<int> const&, Foam::List<int> const&) at ??:?
#4 Foam::mappedPatchBase::calcMapping() const at ??:?
#5 void Foam::mappedPatchBase::distribute<Foam::Vector<dou ble> >(Foam::List<Foam::Vector<double> >&) const at ??:?
#6 Foam::mappedPatchFieldBase<Foam::Vector<double> >::mappedField() const at ??:?
#7 Foam::mappedFixedValueFvPatchField<Foam::Vector<do uble> >::updateCoeffs() at ??:?
#8 Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh>::GeometricBoundaryField::updateCoef fs() at ??:?
#9 Foam::fvMatrix<Foam::Vector<double> >::fvMatrix(Foam::GeometricField<Foam::Vector<doub le>, Foam::fvPatchField, Foam::volMesh> const&, Foam::dimensionSet const&) at ??:?
#10
at ??:?
#11
at ??:?
#12 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#13
at ??:?