# convergence problem in steady state simulation of centrifugal fan in openfoam

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November 22, 2019, 02:35
convergence problem in steady state simulation of centrifugal fan in openfoam
#1
New Member

rohan majalekar
Join Date: Aug 2018
Posts: 3
Rep Power: 6
hello,
I am new to openfoam and trying to simulate centrifugal fan with steady state, in-compressible, turbulent flow(realizableKE model) MRF approach using simpleFoam solver. The problem is solution is not converging(after not 10000 iterations) and values of U & P are in order of 10^3 & 10^9.

Initial & Boundary conditions
1. P
dimensions [0 2 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{
Rotar
{
}

Inlet
{
type fixedValue;
value uniform 84104.28;// atm pressure nearly 1 bar
}

Outlet
{

}

Wall
{
}

}
2.U
dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
Rotar
{
type noSlip;

}

Inlet
{
type pressureInletVelocity;
value uniform (0 0 0);
}

Outlet
{
type flowRateOutletVelocity ;
volumetricFlowRate 0.0452;//=2712 lpm
value uniform (0 0 0);
}

Wall
{
type noSlip;
}
}
3.epsilon
dimensions [0 2 -3 0 0 0 0];

internalField uniform 5.604;

boundaryField
{
Rotar
{
type epsilonWallFunction;
value uniform 5.604;
}

Wall
{
type epsilonWallFunction;
value uniform 5.604;
}

Inlet
{
type fixedValue;
value uniform 5.604;
}

Outlet
{
}
}
4. k
dimensions [0 2 -2 0 0 0 0];

internalField uniform 0.91;

boundaryField
{
Rotar
{
type kqRWallFunction;
value uniform 0.91;
}

Wall
{
type kqRWallFunction;
value uniform 0.91;
}

Inlet
{
;
type turbulentIntensityKineticEnergyInlet;
intensity 0.02; //
value uniform 0.91; //
}

Outlet
{
}

}
5.MRF properties
MRF1
{
cellZone Fan;
active yes;

// Fixed patches (by default they 'move' with the MRF zone)
nonRotatingPatches ();

origin (0 0 105);
axis (0 0 1);
omega -50;//477rpm
}
6.fvSchemes
ddtSchemes
{
}

{
default Gauss linear;
}

divSchemes
{
default none;
div(phi,U) Gauss upwind;
div(phi,k) Gauss upwind ;
div(phi,epsilon) Gauss upwind ;
}

laplacianSchemes
{
default Gauss linear corrected;
}

interpolationSchemes
{
default linear;
}

{
default corrected;
}
wallDist
{
method meshWave;
}
7.fvSolution
solvers
{
p
{
solver GAMG;
tolerance 1e-02;
relTol 0.05;
smoother GaussSeidel;
nCellsInCoarsestLevel 20;
}

U
{
solver smoothSolver;
smoother GaussSeidel;
nSweeps 2;
tolerance 1e-02;
relTol 0.1;
}

k
{
solver smoothSolver;
smoother GaussSeidel;
nSweeps 2;
tolerance 1e-02;
relTol 0.1;
}

epsilon
{
solver smoothSolver;
smoother GaussSeidel;
nSweeps 2;
tolerance 1e-02;
relTol 0.1;
}
}

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

relaxationFactors
{
fields
{
p 0.3;
}
equations
{
U 0.7;
k 0.3;
epsilon 0.3;
}
}

whether boundary conditions, units, MRF or tubulent model is going wrong??
Attached Images
 velocity vectors.jpg (77.3 KB, 27 views)

 Tags centrifugal fan, mrfproperties, openfoam, turbulence modelling