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[mesh manipulation] manipulation of an unstructerd mesh

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Old   February 17, 2020, 14:19
Question manipulation of an unstructerd mesh
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hey foamers,

I'm doing an exhaust gas dispersion simulation with OF4.1. I have recieved an unstructered mesh from an external party. This is a circular domain with a ship in the middle. I want to check the effect of a modified velocity profile on the exhaust gas dispersion. on the domain boundary i am using groovyBC with tabulated values:
/0 -> U
Domain
{
type groovyBC;
fields (z U);
lookuptables
(
{
name Uval;
outOfBounds clamp;
fileName "$FOAM_CASE/0/zU.data";

}
);
valueExpression "(vector(cos(a*pi/180),sin(a*pi/180),0)*Uval(pos().z)-ship)";
gradientExpression "vector(0,0,0)";
fractionExpression "(phi > 0 ) ? 0 : 1";
variables
(
"Uref=15.14;"
"a=280;"
"ship=vector(20,0,0);"
);
}

which is working !!
However the domain has a radius of 2500 meter, when the velocity has reached the ship the profile has already grown towards an atmospheric boundary layer.
To solve this i want to cut this mesh on the windward side such that it only has a 100 meter to reach the ship.
I tried to do this using topoSet and than subset mesh
/system -> topoSetDict:
actions
(
{
name a;
type cellSet;
action new;
source boxToCell;
sourceInfo
{
box (3000 3000 500)(-3000 100 0);
}

name a;
type cellSet;
action invert;
}

>>>topoSet &>log.topoSet
log.topoSet:
Time = 0
mesh not changed.
Created cellSet a
Applying source boxToCell
Adding cells with center within boxes 1((3000 3000 500) (-3000 100 0))
cellSet a now size 0
Time = 0
mesh not changed.
Read set cellSet a with size 0
Inverting cellSet
cellSet a now size 37343105


>>>subsetMesh -overwrite a -patch Domain &>log.subsetMesh
log.subsetMesh:
Subsetting field nut
Subsetting field k
Subsetting field S
Subsetting field p_rgh
Subsetting field alphat
Subsetting field p
Subsetting field T
Subsetting field omega
Subsetting field U
--> FOAM Warning :
From function groovyBCFvPatchField<Type>::groovyBCFvPatchField(c onst fvPatch& p,const DimensionedField<Type, volMesh>& iF,const dictionary& dict)
in file groovyBCFvPatchField.C at line 131
No value defined for U on Domain therefore using the internal field next to the patch
Writing subsetted mesh and fields to time 0

I think the FOAM warning comes from the fact that the table is only used when actually simulating, thus it does not have a value when manipulating the mesh. When launching the simulation this warning is found in every log-file until the solver is employed and just runs smoothly.

i tried out topoSet with subsetMesh command on a simple blockmesh which works as intended, but when i try it on this unstructured mesh it does not change the mesh when i review the result in paraview.

Does anybody know what i am doing wrong, or does someone have a different method for manipulation a unstructured mesh? Furthermore another method on how to impose a modified velocity profile in the internalfield of this mesh is more than welcome.

I know openFOAM able to do this!!!
Thanks in advance.
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mesh manipulation, subsetmesh, toposet, unstructured mesh

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