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Weird aerodynamic forces on 3D body.

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Old   June 12, 2020, 07:43
Default Weird aerodynamic forces on 3D body.
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Aurora
Join Date: May 2020
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Ducagirl is on a distinguished road
Hello everyone!

I am quite newbie with OpenFoam and I am doing an aerodynamic laminar simulation around a .STL file. The results for p and U seem pretty good, but now I have tried to calculate forces and coefficients and the look quite inconsistent.

The objetc is a mount situated in the top of a yatch (only air influence), and I have recreated some damages into the surface in order to compare the different levels of injuries.

I attatch the screenshot of my results after 500 iterations, and also the controlDict script and functions it uses:



Quote:
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 7
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application simpleFoam;

startFrom startTime;

startTime 0;

stopAt endTime;

endTime 500;

deltaT 1;

writeControl timeStep;

writeInterval 50;

purgeWrite 0;

writeFormat ascii;

writePrecision 6;

writeCompression off;

timeFormat general;

timePrecision 6;

runTimeModifiable true;

functions
{
#include "forceCoeffs"
#include "forces"
#includeFunc residuals
}


// ************************************************** *********************** //

Quote:
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 7
\\/ M anipulation |
\*---------------------------------------------------------------------------*/

forces
{
type forces;

libs ("libforces.so");

writeControl timeStep;
timeInterval 1;

log yes;

patches (soporte);
rho rhoInf; // Indicates incompressible
log true;
rhoInf 1; // Redundant for incompressible

CofR (0 0 0); // Rotation around centre line of propeller
pitchAxis (0 0 1);
}


// ************************************************** *********************** //

Quote:
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 7
\\/ M anipulation |
\*---------------------------------------------------------------------------*/

forceCoeffs
{
type forceCoeffs;

libs ("libforces.so");

writeControl timeStep;
timeInterval 1;

log yes;

patches (soporte);
rho rhoInf; // Indicates incompressible
rhoInf 1; // Redundant for incompressible
liftDir (0 1 0);
dragDir (1 0 0);
CofR (0 0 0); // Axle midpoint on ground
pitchAxis (0 0 1);
magUInf 13;
lRef 0.6; // Wheelbase length
Aref 0.617; // Estimated
/*
binData
{
nBin 20; // output data into 20 bins
direction (1 0 0); // bin direction
cumulative yes;
}
*/
}


// ************************************************** *********************** //

Thank you for your help!

Aurora.
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