CFD Online Discussion Forums - UDF for planetary motion

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UDF for planetary motion

Hello everyone, iam new to openfoam and for my project i need to describe planetary motion for two blades around one center blade. iam using overPimpleDyMFoam so can anyone point out the right direction to achieve this:confused:. Where and how to write UDF?
And how to link it with my present solver?
thanks

Greetings Ansh and welcome to the forum,

No UDF should be necessary. Since you are likely using OpenfOAM-v1806, please study the respective OpenFOAM Tutorial Guide: https://www.openfoam.com/documentation/tutorial-guide/ - this will give you a better basis on how to get things to work.

Then once you are more familiar with how OpenFOAM works, check the tutorial case "tutorials/multiphase/overInterDyMFoam/boatAndPropeller/" and in the file "constant/dynamicMeshDict" you will start to see how the moving parts are defined...

Best regards,
Bruno

thanks for quick reply, i have started looking into mentioned tutorials. after adjusting that dynamicmeshdict according to my need iam getting following error:confused:

--> FOAM FATAL ERROR:
Could not find rho:rho

From function void Foam::functionObjects::forces::initialise()
in file forces/forces.C at line 204.

FOAM exiting

i have found other threads related to this bug and i have changed my rhoName to rho as you mentioned there still iam getting this error. Any suggestions

function for force in controldict:

functions
{
forces
{
type forces;
functionObjectLibs ("libforces.so");
writeControl timeStep;
writeInterval 5;
patches (hole1);
rho rhoInf;

rhoInf 1;
CofR (0 0 0);
p p;
U U;
log yes;
verbose true;
}
}

Quick answer: Details, details, details... I need details... Please check the following thread for more information on how to provide mode details: https://www.cfd-online.com/Forums/op...-get-help.html

Because my best guess right now is that you've used the wrong command to start the simulation... :(
What I mean is that the "rho" field should exist when the solver starts running... so if it doesn't exist, then it might mean that you've tried using it with the wrong application.

overPimpleDymFoam rigid body motion rho not found

iam intending to use rigid body motion in overPimpleDyMFoam since i want to give planetary motion to the blades (fig is attached) Attachment 66213
where outer two blades will rotate and revolve arround the centre blade.

I have followed the overInterDyMFoam from multiphase flow to achieve that motion
iam attaching my conrolDict,forceCoeffs and dynamicMeshDict for reference

dynamicMeshDict

Code:

motionSolverLibs    ("librigidBodyMeshMotion.so");



dynamicFvMesh       dynamicOversetFvMesh;



//dynamicOversetFvMeshCoeffs

//{

//    layerRelax 0.3;

//}



motionSolver          rigidBodyMotion;



solver

    {

        type Newmark;

        gamma   0.1;    // Velocity integration coefficient

        beta    0.1;    // Position integration coefficient

    }



    accelerationRelaxation 1.0;



    //- prescribedRotation requires some sub-iterations to converge faster

    //  to desired value.

    nIter   3;



bodies

    {

        movingzone2

        {

            type            rigidBody;

            parent          root;



            // Cuboid mass -- very simple setup. For more complicated shapes

            // see utility surfaceInertia

            mass            9;

            rho             1;

            inertia         (0.05 0 0 0.05 0 0.05);

            centreOfMass    (0.21 -0.07 0); // relative to the centreOfMass

                                            // of parent body

                                            // (here root = global coord system)



            // Transformation tensor and centre of rotation

            transform       (1 0 0 0 1 0 0 0 1) (0.21 0 0);



            joint

            {

                type            composite;

                joints

                (

                    {

                        type Pxyz;  // Allow movement in any direction

                    }

                    {

                        type Rxyz;  // Allow rotation along any axis

                                    // (local - body CS)

                    }

                );

            }



            patches         (hole2);

            innerDistance   100;    // With overset we want to avoid the mesh

                                    // deformation so have large innerDistance

            outerDistance   200;

        } // end hull



        movingzone1

        {



            type            rigidBody;

            parent          movingzone2;



            centreOfMass    (-0.228 0.0 0);

            mass            1;

            rho             1;

            inertia         (0.001 0 0 0.001 0 0.001);

            transform       (1 0 0 0 1 0 0 0 1) (-0.228 0 0);

            patches        (hole1);

            innerDistance   100;

            outerDistance   200;

            joint

            {

                type            Rx;

            }

        } //end propeller



        movingzone3

        {

            type            rigidBody;

            parent          movingzone2;//root;

            centreOfMass    (-0.265 0 0);

            mass            1;

            rho             1;

            inertia         (0.001 0 0 0.001 0 0.001);

            transform       (1 0 0 0 1 0 0 0 1) (-0.265 0 0);

            patches        (hole3);

            innerDistance   100;

            outerDistance   200;

            joint

            {

                type            Ry;

            }

        }

         solid-background

        {

            type            rigidBody;

            parent          movingzone2;//root;

            centreOfMass    (-0.265 0 0);

            mass            1;

            rho             1;

            inertia         (0.001 0 0 0.001 0 0.001);

            transform       (1 0 0 0 1 0 0 0 1) (-0.265 0 0);

            patches        (hole3);

            innerDistance   100;

            outerDistance   200;

            joint

            {

                type            Ry;

            }

        }

    }



    restraints

    {

        movingzone1Rotation

        {

            type                    prescribedRotation;

            body                    movingzone1;

            referenceOrientation    (1 0 0 0 1 0 0 0 1);

            axis                    (0 1 0);    // Axis of rotation

            omega                   sine;       // Function1 entry

            omegaCoeffs

            {

                frequency   4;

                amplitude   0.2;

                scale       (0 1 0);

                level       (0 1 0);

            }

        }

        movingzone3Rotation

        {

            type                    prescribedRotation;

            body                    movingzone3;

            referenceOrientation    (1 0 0 0 1 0 0 0 1);

            axis                    (1 0 0);

            omega                   table

            (

                (0 (0 0 0))

                (1 (16 0 0))

            );

        }

     }

}

controlDict

Code:

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    object      controlDict;

}

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



libs            ("liboverset.so" "librigidBodyDynamics.so");



application     overPimpleDyMFoam;



startFrom       startTime;



startTime       0;



stopAt          endTime;



endTime         5;



deltaT          0.0000000025;



writeControl    adjustableRunTime;



writeInterval   0.005;



purgeWrite      0;



writeFormat     binary;



writePrecision  10;



writeCompression off;



timeFormat      general;



timePrecision   6;



runTimeModifiable true;



adjustTimeStep  yes;



//maxCo           1;

maxCo           5.0;

maxAlphaCo      5.0;

maxDeltaT       1;





functions

{

     #include "forceCoeffs"

}

forceCoeffs

Code:

forceCoeffs

{

    



    functionObjectLibs      ("libforces.so");



    writeControl    timeStep;

    timeInterval    1;



    patches         (walls);

    rho         rhoInf;      // Indicates incompressible

    rhoInf      1; 

    p           p;

    U           U;

    // Redundant for incompressible

    liftDir         (0 0 1);

    dragDir         (1 0 0);

    CofR            (0 0 0);  // Axle midpoint on ground

    pitchAxis       (0 1 0);

    magUInf         20;

    lRef            1.42;        // Wheelbase length

    Aref            0.75;        // Estimated

    /*

    binData

    {

        nBin        20;          // output data into 20 bins

        direction   (1 0 0);     // bin direction

        cumulative  yes;

    }

    */

}

and error that iam getting

Code:

Creating interpolatedCells field 



Selecting incompressible transport model Newtonian

Selecting turbulence model type laminar

Selecting laminar stress model Stokes

Reading/calculating face velocity Uf



No MRF models present



No finite volume options present

Courant Number mean: 0 max: 0



Starting time loop



Courant Number mean: 0 max: 0

deltaT = 2.9999994e-09

Time = 3e-09



forces forces:

    Not including porosity effects







--> FOAM FATAL ERROR: 

Could not find rho:rho



    From function void Foam::functionObjects::forces::initialise()

    in file forces/forces.C at line 204.



FOAM exiting

Quote:

What I mean is that the "rho" field should exist when the solver starts running... so if it doesn't exist, then it might mean that you've tried using it with the wrong application

1)does that mean i cannot use rigid body motion with overPimpleDyMFoam(since while using it only i have started facing this error )

2)can anyone recommend any literature available related to this?
pardon my immaturity with openfoam:o

Quick answers:

1. I've tested with OpenFOAM-v1806 as a Docker image. I used the tutorial case "incompressible/overPimpleDyMFoam/twoSimpleRotors" as a basis and did the modifications that you mentioned to the controlDict file, namely:

Added the entry for "forceCoeffs" in the "functions"...
And created the file "system/forceCoeffs", although I had to add this line in order for it to work:

Code:

type forceCoeffs;

namely having the content of the file like this:

Code:

forceCoeffs { type forceCoeffs; functionObjectLibs ("libforces.so"); writeControl timeStep; timeInterval 1; patches (walls); rho rhoInf; // Indicates incompressible rhoInf 1; p p; U U; // Redundant for incompressible liftDir (0 0 1); dragDir (1 0 0); CofR (0 0 0); // Axle midpoint on ground pitchAxis (0 1 0); magUInf 20; lRef 1.42; // Wheelbase length Aref 0.75; // Estimated /* binData { nBin 20; // output data into 20 bins direction (1 0 0); // bin direction cumulative yes; } */ }

Then I run the solver and everything works just fine, namely it will make the calculations while it is simulating.

It also worked when I ran the solver with the "-postProcess" option, after I had a few time steps already written to disk:

Code:

overPimpleDyMFoam -postProcess

Mmmmm... this sounds like either a bug or some detail is missing for that type of rigid body motion... You may want to report this at http://develop.openfoam.com/ - although you may need to provide a simple test case, so that it's easier to reproduce the problem and fix it.

2. The documentation provided here: https://www.openfoam.com/documentation/ - should already have a considerable amount of information... check the "Extended Code Guide" page for more details, although it may be a bit confusing at first to navigate there.