CFD Online Discussion Forums - Pitching Airfoil angle of attack

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Pitching Airfoil angle of attack

Hello formers
I have been doing an airfoil pitching case in OpenFOAM and I was able to do the pitching from angle 0 to -1. But I have to do a pitching case such that the airfoil starts from 0 to -1 and then to +1 and so on in an oscillatory form.

My dynamicMeshDict for 0 to -1 is given below

Code:

dynamicFvMesh      dynamicMotionSolverFvMesh;



motionSolverLibs ("libsixDoFRigidBodyMotion.so");



solver            sixDoFRigidBodyMotion;



sixDoFRigidBodyMotionCoeffs

{

    patches         (wing);

    innerDistance   0.3;

    outerDistance   1;



    mass                60;

    centreOfMass    (0.25 0 0);

    momentOfInertia (0.09408 0.17475 1.5296);

    orientation

    (

        0.999847695 -0.017452406 0

        0.017452406 0.999847695 0

        0 0 1

    );

    angularMomentum   (0 0 0.25);

    g                            (0 -9.81 0);

    rhoName                 rhoInf;

    rhoInf                      1;

    report                      on;



    constraints

    {

        yLine

        {

            sixDoFRigidBodyMotionConstraint line;

            centreOfRotation    (0.25 0 0);

            direction                 (0 1 0);

        }



        zAxis

        {

            sixDoFRigidBodyMotionConstraint axis;

            axis                (0 0 1);

        }

    }



    restraints

    {

        verticalSpring

        {

            sixDoFRigidBodyMotionRestraint linearSpring;



            anchor               (0.25 0 0);

            refAttachmentPt (0.25 0 0);

            stiffness            4000;

            damping             2;

            restLength          0;

        }



        axialSpring

        {

            sixDoFRigidBodyMotionRestraint linearAxialAngularSpring;



            axis                 (0 0 1);

            stiffness          700;

            damping           0.5;

            referenceOrientation $orientation;

        }

    }

}

Can anybody tell me how I can generate an oscillatory airfoil pitching in OpenFOAM.
The solver I am using is rhoPimpleDyMFoam.

Oscillating pitching airfoil

I am trying to do an oscillating pitching airfoil in rhoPimpleDyMFoam in subsonic mach. But in my case the oscillation is in the form of 1.02cos(omega*t) but in oscillatingRotatingMotion the rotating motion is given as amplitude*sin(omega*t) and also my rotation is only going in +ve direction and not in -ve direction. Can anyone help me resolve the problem?

Pitching Airfoil angle of attack

I am doing a pitching airfoil in rhoPimpleDyMFoam and according to oscillatingRotatingMotion the angle of attack is calculated using "vector eulerAngles = amplitude_*sin(omega_*t)". In my case the pitching should be "amplitude_*cos(omega_*t)". Can anybody suggest how can I solve this problem.

I tried changing in the oscillatingRotatingMotion.C file but it wont work.

Please give suggessions?

Hello there,
A Good Evening to you!

I am not sure what you are suggesting can work.... Basically, the oscillatory motion rotates part of the mesh as per the enforced function. In the current implementation, this function is:

theta = amplitude * sin(omega * t)

I dont think you can change that to:

theta = amplitude * cos(omega * t)

If you think about it, y = A*cos(w*t) at time t = 0 will give the result y = A. This would imply that at the beginning of you simulation, at time t = 0, you want the mesh to suddenly jump to its maximum position, which does not make sense.

The reason why you use y = A*sin(w*t) is because at time t = 0, Y = 0, which means, that the mesh starts at its initial position, and with time slowly moves from this initial position to its maxima (Y = A) and back.

Hope this helps clear things up :-)

Regards,
Philippose

Thank you for the reply

import mesh in pimpleDyMFoam

hi everyone
I try to import a mesh from gambit to openfoam. I have inner circle with domain of Rectangular. My boundary condition between circle and rectangular is interface.
The openfoam did not accept these boundaries and change it to a default wall.
How can i change them?
:confused:

Quote:

Originally Posted by albinjohny (Post 546814)

Code:

dynamicFvMesh      dynamicMotionSolverFvMesh;



motionSolverLibs ("libsixDoFRigidBodyMotion.so");



solver            sixDoFRigidBodyMotion;



sixDoFRigidBodyMotionCoeffs

{

    patches         (wing);

    innerDistance   0.3;

    outerDistance   1;



    mass                60;

    centreOfMass    (0.25 0 0);

    momentOfInertia (0.09408 0.17475 1.5296);

    orientation

    (

        0.999847695 -0.017452406 0

        0.017452406 0.999847695 0

        0 0 1

    );

    angularMomentum   (0 0 0.25);

    g                            (0 -9.81 0);

    rhoName                 rhoInf;

    rhoInf                      1;

    report                      on;



    constraints

    {

        yLine

        {

            sixDoFRigidBodyMotionConstraint line;

            centreOfRotation    (0.25 0 0);

            direction                 (0 1 0);

        }



        zAxis

        {

            sixDoFRigidBodyMotionConstraint axis;

            axis                (0 0 1);

        }

    }



    restraints

    {

        verticalSpring

        {

            sixDoFRigidBodyMotionRestraint linearSpring;



            anchor               (0.25 0 0);

            refAttachmentPt (0.25 0 0);

            stiffness            4000;

            damping             2;

            restLength          0;

        }



        axialSpring

        {

            sixDoFRigidBodyMotionRestraint linearAxialAngularSpring;



            axis                 (0 0 1);

            stiffness          700;

            damping           0.5;

            referenceOrientation $orientation;

        }

    }

}

Can anybody tell me how I can generate an oscillatory airfoil pitching in OpenFOAM.
The solver I am using is rhoPimpleDyMFoam.

Hi

My case in openfoam is exactly same as yours but i use pimpledymfoam alone.
I am afraid if it is possible to explain how to import mesh and how to make generate boundaries around airfoil?

thank you in advance

Hi everyone
I am simulating a 2d airfoil pitching with some freestream. i am using solidBodyMotion (OscillatingRotatingMotion). I am confused about the parameters origin and amplitude in the dynamicMeshDict. Can anyone tell me how to set this parameters for a 2d airfoil.
regards
Chayanit

@Chayanit
check this link: https://openfoamwiki.net/index.php/P...dyMotionFvMesh

origin: The origin of rotation. This will be the rotation point.
amplitude: This is the amplitude of the rotating motion. The rotating motion amplitude is provided as a 3D vector definition. The total magnitude of the vector provides the amplitude of the motion. The individual component directions specify the axis of rotating oscillation. Rotation will oscillate about this axis. All component directions oscillate at the same frequency. Motion is defined in units of rad.

Thank you so much.
That means if I want to rotate about z-axis with an angle of 1 rad, I should put amplitude (0 0 1) and if the rotation axis is x=0.25, then I should put origin (0.25 0 0).
Am I correct?

Quote:

Originally Posted by CHAYANIT (Post 715586)

Yes, that's correct except that the angles for amplitude are in degrees, not radians. But omega is in rad/s.

Quote:

Originally Posted by Evren Linda (Post 715803)

Yes, that's correct

Thank you so much.