[FluidKo]

solvers
{
    p
    {
        solver          GAMG;
        smoother        GaussSeidel;
        tolerance       1e-6;
        relTol          0.1;
    }

    "(U|k|omega|epsilon)"
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-6;
        relTol          0.1;
    }
}

SIMPLE
{
    residualControl
    {
        p               1e-4;
        U               1e-4;
        "(k|omega|epsilon)" 1e-4;
    }
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       0;

}

potentialFlow
{
    nNonOrthogonalCorrectors 10;
}

relaxationFactors
{
    fields
    {
        p               0.3;
    }
    equations
    {
        U               0.7;
        "(k|omega|epsilon).*" 0.7;
    }
}

Hello everybody~
I'm wondering tolerance in simpleFoam.
Upper code is one of simple algorithm codes in tutorial file.
In this code, there are 2 types of tolerance.
One is tolerance in 'solvers' part and another is tolerance in 'residualControl' part.
I want to know difference between them.

Acutally I've learned PIMPLE algorithm before.
For the case of PIMPLE algorithm, I know difference between tolerance in 'solvers' part and tolerance in 'residualControl' part.
Tolerance in 'solvers' part is criteria of residual for pressure correction(inner loop) and tolerance in 'residualControl' part is criteria of residual for momentum prediction(outer loop).

But for the case of SIMPLE algorithm there is only momentum prediction(outer loop), not pressure correction(inner loop).
Even though there is only momentum prediction, why there can be 2 criterias(tolerance in 'solvers' and tolerance in 'residualControl')?

What is difference between them for SIMPLE algorithm?

Thank you~!