# MRF SimpleFoam - Wind Turbine Blade - Underestimating forces

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October 28, 2021, 12:00
MRF SimpleFoam - Wind Turbine Blade - Underestimating forces
#1
New Member

Join Date: Sep 2021
Posts: 6
Rep Power: 4
Hello,

I am trying to simulate in a steady flow a 15 MW IEA turbine blade in a 120° axisymmetric wedge domain.
The size of the domain is 2 radii in front of the blade, 5 radii behind and 1.5 radii high.
There are 2 regions in the mesh: Rotor that moves at -0.76 rad/s, and external wedge (cunha_externa) that is stationary.
The moment at x, converged at -1.72E+6Nm. Whereas by the technical parameters approx. -5.7E+6Nm is expected (power coefficient (cp) = 0.489).
I don't know what I am doing wrong, with the dynamic mesh method and transient solver I achieved the results.
I'm using the simplefoam solver with mrf.
The turbulence model is K Omega SST.
Definition of iea 15mw: https://www.nrel.gov/docs/fy20osti/75698.pdf
Mesh and results: https://drive.google.com/drive/folde...bC?usp=sharing
I tried to simulate a in a similar way of the case iv from this article (https://doi.org/10.1016/j.renene.2018.07.062)
Boundaries:
U
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2106                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      binary;
arch        "LSB;label=32;scalar=64";
class       volVectorField;
location    "0";
object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (-10 0 0);

boundaryField
{
pa
{
type            noSlip;
}
{
type            fixedValue;
value           \$internalField;
}
saida
{
}
{
type            cyclicAMI;
}
"(AMI_1|AMI_2)"
{
type            cyclicAMI;
}
}

// ************************************************************************* //```
p
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2106                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      binary;
arch        "LSB;label=32;scalar=64";
class       volScalarField;
location    "0";
object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
{
}
saida
{
type            fixedValue;
value           \$internalField;
}
{
type            cyclicAMI;
}
"(AMI_1|AMI_2)"
{
type            cyclicAMI;
}
}

// ************************************************************************* //```
k
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2106                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      binary;
arch        "LSB;label=32;scalar=64";
class       volScalarField;
location    "0";
object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0.06;

boundaryField
{
pa
{
type            kqRWallFunction;
value           \$internalField;
}
{
type            fixedValue;
value           \$internalField;
}
saida
{
}
{
type            cyclicAMI;
}
"(AMI_1|AMI_2)"
{
type            cyclicAMI;
}
}

// ************************************************************************* //```
omega
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2106                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      binary;
arch        "LSB;label=32;scalar=64";
class       volScalarField;
location    "0";
object      omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 4.5939;

boundaryField
{
pa
{
type            omegaWallFunction;
value           \$internalField;
}
{
type            fixedValue;
value           \$internalField;
}
saida
{
}
{
type            cyclicAMI;
}
"(AMI_1|AMI_2)"
{
type            cyclicAMI;
}
}

// ************************************************************************* //```
nut
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2106                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      binary;
arch        "LSB;label=32;scalar=64";
class       volScalarField;
location    "0";
object      nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -1 0 0 0 0];

internalField   uniform 0;

boundaryField
{
pa
{
type            nutkWallFunction;
value           \$internalField;
}
{
type            calculated;
value           \$internalField;
}
{
type            cyclicAMI;
}
"(AMI_1|AMI_2)"
{
type            cyclicAMI;
}
}

// ************************************************************************* //```
MRFProperties
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2106                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      ascii;
class       dictionary;
object      MRFProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

MRF1
{
cellZone    Rotor_zone;
active      yes;

// Fixed patches (by default they 'move' with the MRF zone)
nonRotatingPatches (AMI_1 AMI_2);
origin      (0 0 0);
axis        (1 0 0);
omega       0.769230769231; // rad/s
}

// ************************************************************************* //```
fvSchemes
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      ascii;
class       dictionary;
location    "system";
object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
}

{
default	Gauss linear;
}

divSchemes
{
default         none;
div(phi,U)      bounded Gauss linearUpwind grad(U);
div(phi,omega)	Gauss upwind;
div(phi,k)	Gauss upwind;
}

laplacianSchemes
{
default	Gauss linear corrected;
}

{
default	corrected;
}

wallDist
{
method	meshWave;
}

// ************************************************************************* //```
fvSolution
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      ascii;
class       dictionary;
location    "system";
object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
p
{
solver          GAMG;
tolerance       1e-7;
relTol          0;
smoother        GaussSeidel;
cacheAgglomeration no;
maxIter	500;
}

"(U|k|omega)"
{
solver          smoothSolver;
smoother        GaussSeidel;
tolerance       1e-7;
relTol          0;
nSweeps         2;
}
}
SIMPLE
{
nNonOrthogonalCorrectors 0;
consistent      yes;
pRefCell	0;
pRefValue	0;
residualControl
{
p	1e-6;
"(U|k|omega)"	1e-6;
}
}

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

// ************************************************************************* //```
forcesImcompressible
Code:
```/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      ascii;
class       dictionary;
object      forcesIncompressible;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

forces
{
functionObjectLibs 	("libforces.so");

patches     		(pa);
CofR        		(3.770655 0 0);
pitchAxis   		(0 0 0);
writeInterval		1;
type            	forces;
pName           	p;
UName           	U;
rho         		rhoInf; // Incompressible solver
rhoInf      		1.18732;
log             	true;
}

// ************************************************************************* //```
checkMesh
Code:
```/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2106                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : _7b82832f-20210625 OPENFOAM=2106
Arch   : "LSB;label=32;scalar=64"
Exec   : checkMesh
Date   : Oct 28 2021
Time   : 12:36:07
Host   : DESKTOP-H7B8IOF
PID    : 510
I/O    : uncollated
Case   : iea_15mw
nProcs : 1
trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 5, maxFileModificationPolls 20)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0

Time = 0

Mesh stats
points:           15087385
faces:            43973155
internal faces:   43441104
cells:            14447935
faces per cell:   6.050294
boundary patches: 8
point zones:      0
face zones:       0
cell zones:       2

Overall number of cells of each type:
hexahedra:     13867146
prisms:        153181
wedges:        0
pyramids:      0
tet wedges:    129
tetrahedra:    0
polyhedra:     427479
Breakdown of polyhedra by number of faces:
faces   number of cells
4   8873
5   7662
6   65466
7   150255
8   20204
9   117862
10   552
11   119
12   50013
13   2
14   19
15   6408
18   44

Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
*Number of regions: 2
The mesh has multiple regions which are not connected by any face.
<<Writing region information to "0/cellToRegion"
<<Writing region 0 with 4975517 cells to cellSet region0
<<Writing region 1 with 9472418 cells to cellSet region1

Checking patch topology for multiply connected surfaces...
Patch    Faces   Points                  Surface topology
entrada     8482     8557  ok (non-closed singly connected)
saida     8482     8557  ok (non-closed singly connected)
lado0    46631    48006  ok (non-closed singly connected)
lado120    46736    48116  ok (non-closed singly connected)
lateral    68880    69465  ok (non-closed singly connected)
pa   274482   283476  ok (non-closed singly connected)
AMI_2    39182    39181  ok (non-closed singly connected)
AMI_1    39176    39405  ok (non-closed singly connected)

Checking faceZone topology for multiply connected surfaces...
No faceZones found.

Checking basic cellZone addressing...
CellZone        Cells       Points       VolumeBoundingBox
cunha_externa      4975517      5070077 2.821492e+07 (-600 -155.8846 -3.64628e-16) (240 155.8846 180)
Rotor_zone      9472418     10017308     282470.2 (-4.006414 -112.5832 -1.408003e-05) (12.00412 112.5835 130)

Checking geometry...
Overall domain bounding box (-600 -155.8846 -1.408003e-05) (240 155.8846 180)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (2.330773e-17 7.088203e-16 5.225327e-14) OK.
Max cell openness = 3.308378e-15 OK.
Max aspect ratio = 66.99643 OK.
Minimum face area = 3.874454e-06. Maximum face area = 8.968646.  Face area magnitudes OK.
Min volume = 1.148255e-06. Max volume = 11.81478.  Total volume = 2.849739e+07.  Cell volumes OK.
Mesh non-orthogonality Max: 63.7486 average: 4.455527
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 3.998489 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End```
Thank you for the advice,
Attached Images
 mesh1.jpg (19.2 KB, 64 views) U_90.jpg (29.3 KB, 54 views) U_90_close.jpg (23.3 KB, 43 views) U_90x.jpg (21.8 KB, 40 views) U_90y.jpg (22.5 KB, 39 views)

March 16, 2022, 06:32
#2
New Member

Join Date: Sep 2021
Posts: 6
Rep Power: 4
Solution:
Increase the MRF domain (non inertial) to 2 blade diameters of lenght and 2 blade diameters of height with the blade in the middle
Attached Images
 q001velocitycontour_yplane-min.jpg (42.0 KB, 53 views) p07-min.jpg (23.8 KB, 37 views)

 Tags mrf, simplefoam, wedge 120°, wind turbine blade

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