On the non-convergence of RheoTool simulation of millimeter-scale geometric models

[tiankai7411]

Hi, I am using RheoTool to simulate a 2D square cavity flow and have found that a slightly larger inlet velocity or flow rate results in non-convergence. The geometric length is 36mm, the width is 4mm, and the side length of the rectangular cavity is 4mm. the generated meshes are all square meshes. The files are as follows
U
*---------------------------------------------------------------------------*/
FoamFile
{
format ascii;
class volVectorField;
location "0";
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
inlet
{
type fixedValue;
value uniform (0.042 0 0);
}
outlet
{
type zeroGradient;
}
lowerWall
{
type fixedValue;
value uniform (0 0 0);
}
upperWall
{
type fixedValue;
value uniform (0 0 0);
}
frontAndBack
{
type empty;
}
}

physical parameter
parameters
{
type FENE-P;

            rho              rho [1 -3 0 0 0 0 0] 1.;
            etaS             etaS [1 -1 -1 0 0 0 0] .01;
            etaP             etaP [1 -1 -1 0 0 0 0] .99;             
            lambda           lambda [0 0 1 0 0 0 0] 0.5;
            L2               L2 [0 0 0 0 0 0 0] 100;
            solveInTau       false;                

            stabilization    none;                    

}

passiveScalarProperties
{
solvePassiveScalar no;
D D [ 0 2 -1 0 0 0 0 ] 1e-9;
}
controlDict

FoamFile
{
format ascii;
class dictionary;
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application rheoFoam;

startFrom latestTime;

startTime 0;

stopAt endTime;

endTime 5;

deltaT 1e-3;

writeControl runTime;

writeInterval 0.05;

purgeWrite 0;

writeFormat ascii;

writePrecision 12;

writeCompression compressed;

timeFormat general;

timePrecision 10;

graphFormat raw;

runTimeModifiable off;

adjustTimeStep on;

maxCo 0.9;

maxDeltaT 0.001;

FoamFile
{
format ascii;
class dictionary;
object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

fvSchemes

ddtSchemes
{
default Euler;
}

gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
grad(U) Gauss linear;
linExtrapGrad Gauss linear;

}

divSchemes
{
default none;
div(tau) Gauss linear;
div(grad(U)) Gauss linear;
div(phi,U) GaussDefCmpw cubista;
div(phi,1|f) GaussDefCmpw cubista;
div(phi,A) GaussDefCmpw cubista; //A
div(phi,theta) GaussDefCmpw cubista;
div(phi,tau) GaussDefCmpw cubista;
div(phi,C) GaussDefCmpw cubista;
}

laplacianSchemes
{
default none;
laplacian(eta,U) Gauss linear orthogonal;
laplacian(p|(ap-H1)) Gauss linear orthogonal;

}

interpolationSchemes
{
default linear;

}

snGradSchemes
{
default orthogonal;
}

fluxRequired
{
default no;
p;
}

FoamFile
{
format ascii;
class dictionary;
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

fvSolution
solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-10;
relTol 0;
minIter 0;
maxIter 800;

}

U
{

    solver           PBiCG;
    preconditioner
    {
        preconditioner DILU;
    }

    tolerance         1e-8;
    relTol            0;
    minIter           1;
    maxIter           1000;
}

"(theta|tau|C|A)"
{

    solver           PBiCG;
    preconditioner
    {
        preconditioner DILU;
    }

    tolerance         1e-12;
    relTol            0;
    minIter           0;
    maxIter           1000;
}

}

SIMPLE
{
nInIter 1;
nNonOrthogonalCorrectors 0;
pRefCell 0;
pRefValue 0;

residualControl
{
    
}

}

relaxationFactors
{
fields
{
p 0.9;
}

 equations
  { 
    U 0.5;
    tau 0.5;
    theta 0.5;
  }

}
I can't get my head around what's wrong with it. If anyone takes the time to provide some insight, we'll greatly appreciate it.

[tiankai7411]

This is my mesh