Sigh, I just want to solve my simulation problems and get a correct result. It is right or wrong, you think....

.

Wat ??

To remove barckets in bash for a file called crap:

cat crap | sed s/\(//g | sed s/\)//g > crap_nobracket

For the Headers, I would just open remove and save (it is not elegant but easy...)

In Octave, to give it the format you want:

myFile = fopen('<FileName.txt>',"w");
fprintf(myFile,"(%f %f %f)\n",<Vector>);
fclose(myFile);

Does anyone know how to fix this for multiphase flow (e.g. interFoam) and does anyone have an updated force.C which accounts for variable density and viscosity/or instructions saying where to change the file force.C?

Any comments are highly appreciated :)

Thanx,

Andreas

forces and monents in OF1.6
 

I am trying to calculate torque generated by impellar using execFlowFunctionObjects.

Hi Stephane,

I am also using MRFSimpleFoam OF1.6.
I am trying to calculate moment about x.y and z axis.
I get the following error:

Create time
Create mesh for time = 500
Time = 500
Reading phi
Reading U
Reading p
Selecting incompressible transport model Newtonian
Selecting RAS turbulence model kEpsilon
kEpsilonCoeffs
{
Cmu 0.09;
C1 1.44;
C2 1.92;
sigmaEps 1.3;
}

Unknown function type Forces
Table of functionObjects is empty

From function functionObject::New(const word& name, const Time&, const dictionary&)
in file db/functionObjects/functionObject/functionObject.C at line 74.
FOAM exiting

My controlDict is:
application MRFSimpleFoam;
startFrom startTime;
startTime 0;
stopAt endTime;
endTime 500;
deltaT 1;
writeControl timeStep;
writeInterval 50;
purgeWrite 0;
writeFormat ascii;
writePrecision 6;
writeCompression uncompressed;
timeFormat general;
timePrecision 6;
runTimeModifiable yes;

functions
{
forces
{
type Forces;
functionObjectsLibs ("libforces.so");
outputControl outputTime;
patches (Rushton_Turbine_5_To_WALL);
rhoNmae rhoInf;
rhoInf 1.0;
pName p;
Uname U;
log true;
CofR (0 0 0);
}
forceCoeffs
{
type forceCoeffs;
functionObjectsLibs ("libforces.so");
patches (Rushton_Turbine_5_To_WALL);
pName p;
Uname U;
rhoName rhoInf;
rhoInf 1.225;
CofR (0 0 0);
liftDir (0 1 0);
dragDir (1 0 0);
pitchAxis (0 0 0);
magUInf 55.5;
lRef 0.6;
ARef 1;
}
};

What should I do to get the moments? Do I need to change anything else?

Regrads,
Hrushikesh

Hello,
try this !

-----------------

functions
(
forces
{
type forces;
functionObjectsLibs ("libforces.so");
patches (Rushton_Turbine_5_To_WALL);
rhoName rhoInf;
pName p;
Uname U;
rhoInf 1.0;
CofR (0 0 0);
outputControl timeStep;
outputInterval 1;
log true;
}
forceCoeffs
{
type forceCoeffs;
functionObjectsLibs ("libforces.so");
patches (Rushton_Turbine_5_To_WALL);
pName p;
Uname U;
rhoName rhoInf;
rhoInf 1.225;
CofR (0 0 0);
liftDir (0 1 0);
dragDir (1 0 0);
pitchAxis (0 0 0);
magUInf 55.5;
lRef 0.6;
ARef 1;
}
);

-----------------
Regards,
Stephane.

Hi Stephane,

I have tried this. But it gives me following error.

Unknown function type Forces
Table of functionObjects is empty

From function functionObject::New(const word& name, const Time&, const dictionary&)
in file db/functionObjects/functionObject/functionObject.C at line 74.
FOAM exiting

My controlDict is :

---------------------------------

application MRFSimpleFoam;
startFrom startTime;
startTime 0;
stopAt endTime;
endTime 5000;
deltaT 1;
writeControl timeStep;
writeInterval 1000;
purgeWrite 0;
writeFormat ascii;
writePrecision 6;
writeCompression uncompressed;
timeFormat general;
timePrecision 6;
runTimeModifiable yes;

functions
(
forces_turbine
{
type forces;
functionObjectLibs ("libforces.so"); //Lib to load
patches (Rushton_Turbine_5_To_WALL); // change to your patch name
pName p;
Uname U;
rhoName rhoInf;
rhoInf 1; //Reference density for fluid
CofR (0 0 0); //Origin for moment calculations
outputControl timeStep;
outputInterval 1;
log true;
}
);

-------------------------------------------------
This controlDict (only calculate forces) works fine for me.
Warning : 'type forces;' not 'type Forces;'
Stephane.

I have tried your 2nd reply also.
Do we have to modify anything alse in our case directory like changes in 0..
I am still getting the same error:
Unknown function type forces
Table of functionObjects is empty

From function functionObject::New(const word& name, const Time&, const dictionary&)
in file db/functionObjects/functionObject/functionObject.C at line 74.
FOAM exiting

Hrushikesh

Forces in V1.6
 

hi Hrushikes,

try this to get the forces in OpenFOAM 1.6..

functions
(
forces
{
type forceCoeffs;
functionObjectsLibs ("libforces.so");
outputControl timeStep;
outputInterval 1;
patches
{
Rushton_Turbine_5_To_WALL
);
pName p;
Uname U;
log true;
rhoInf 1.225;
CofR (0 0 0);
liftDir (0 1 0);
dragDir (1 0 0);
pitchAxis (0 0 0);
magUInf 55.5;
lRef 0.6;
ARef 1;
}
);

Regards

Naveen
NAL, Bangalore

Hi Naveen,
I have tried the things you have mentioned. But the error still remains.

Unknown function type force_coeffs
Table of functionObjects is empty

From function functionObject::New(const word& name, const Time&, const dictionary&)
in file db/functionObjects/functionObject/functionObject.C at line 74.
FOAM exiting

What do the 1st two lines of error mean?

regards
Hrushikesh

Any update in that matter? I tried different approaches, I mainly followed the following post: http://www.cfd-online.com/Forums/ope...es-of15-8.html

I'm using OpenFOAM 1.7.1 and interFoam solver.

Have a great day everyone!
K

I also tried to use icoFoam solver. In both cases I do not get any force output, neither in the screen output, nor in any file format.

Hi,
I am attaching my controlDict file here. This version of controlDict is working for me (OF 1.6).


application MRFSimpleFoam;
startFrom latestTime;
startTime 0;
stopAt endTime;
endTime 1500;
deltaT 1;
writeControl timeStep;
writeInterval 10;
purgeWrite 0;
writeFormat ascii;
writePrecision 6;
writeCompression uncompressed;
timeFormat general;
timePrecision 6;
runTimeModifiable yes;
functions
{
forces
{
type forces;
functionObjectLibs ("libforces.so"); //Lib to load
patches (Rushton_Turbine_5_To_WALL); // change to your patch name
pName p;
Uname U;
rhoName rhoInf;
rhoInf 1000;
CofR (0.16 0 0); //Origin for moment calculations
outputControl timeStep;
outputInterval 1;
}
}

Hrushi,

Really, really appreciate your post. Your controlDict file worked perfectly fine. At the current moment I'm not sure what exactly made a trick, but it work.

Best,
K

I know the tool is not fully suitable for two-phase flows, but assuming that I only care for water domain (not air) I assume the tool gives acceptable solution.

So trying to use interFoam solver, the solver quits saying it cannot find "nu" in constant/transportProperties. I tried to redefine the code in forces.C, but for now I gave up. I found some work around, to add additional line at the beginning of transportProperties such as:

nu nu [ 0 2 -1 0 0 0 0 ] 1e-06;

Can any of OpenFOAM gurus comment on that? Is such work around acceptable? I think the other two nu-s in phase1 and phase2 are read correctly by the solver.

Thanks,
K

drag & force over a cylinder patch
 

Hi
 

can every one help me that how to solve this error when i want to calculate cd (drag coeff),

No valid model for viscous stress calculation.

From fuction forces::devRhoReff()
in file foeces/forces.C at line 306


i added the turbulence lib & related lib to the solver and compiled it but this error always appear the run is stoped :(

Best, Rasoul

mine BC conditions for pressure is zeroGradient, so I do not know what the pressure is at the farfield. at default pRef is set to 0.

How can I specify the pRef at the freestream pressure ? I have just added this line : pRef -1000; But this did not change anything , apparantly it did not use this value. I am calculating Cl Cd..