[DanFO]

Hello everyone,

My question is simple: How to impose motion to the rotor disk?

I refer to the rotor disk in the tutorial case "rotorDisk" found in: $FOAM_TUTORIALS/incompressible/simpleFoam/rotorDisk.
Or, if you prefer online: https://develop.openfoam.com/Develop...Foam/rotorDisk

I want to impose an oscillatory motion (sinusoidal) to the disk and analyze its transient response. I think the first step is to change the default solver "simpleFoam" (steady-state solver) to "pimpleFoam" (transient solver). And I managed to do this. Second step is to impose the motion, and I know how to do it for a Boundary Field using dynamicMeshDict and pointDisplacement (as we do for an oscillating cylinder). But the problem is that the rotor disk is not a boundary, it is a region of cells inside the domain and I didn't understand clearly how it is defined.

So, I would appreciate if someone could explain how the disk region is defined and how to impose an oscillatory motion to it.

(I'm using OpenFOAM 7, and I'm quite new to the software)

Thank you!

[Ardali]

This question needs a broad range of answer.
For a start check

$FOAM_TUTORIALS/incompressible/simpleFoam/mixerVessel2D
$FOAM_TUTORIALS//incompressible/pimpleFoam/RAS/propeller


search AMI functionality, you will find lots of useful links.
GGI is another functionality which is available only on FOAM-extended versions.
These two are applied on interfaces for a rotor-stator interaction.
MRF functionality is a steady solution for rotor-stator solution.
Good luck
Ardalan

[DanFO]

Hello Ardalan,

I see that your suggestions are great for solving rotational mesh problems. But I don't want to rotate the disk. To better explain my problem: I want to model a floating offshore wind turbine moving up and down with waves. So, to simplify the problem, I want to simulate an actuator disk moving up and down. The whole mesh could move around the disk as for ALE (Arbitrary Lagrangian Eulerian) methods of dynamic mesh. So, how to apply vertical oscillatory motion to the disk?

Thank you for your attention

[Ardali]

Hi,
OK, it seems you want to replicate the effect of tidal wave on your turbine.
Please check

$FOAM_TUTORIALS/incomressible/pimpleFoam/laminar/movingCone


Please also check
$FOAM_TUTORIALS/incomressible/pimpleFoam/RAS/wingMotion


They have different dynamicMeshDict in constant folder.

Ardalan

[DanFO]

Hi Ardalan,

Both tutorial cases impose motion to a boundary.
In the "movingCone" case, it is applied a velocity on the "movingWall" boundary, as we can see on file "0/pointMotionUx":

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

internalField   uniform 0;

boundaryField
{
    movingWall
    {
        type            uniformFixedValue;
        uniformValue    constant 1;
    }
...

In the "wingMotion" case, a displacement is calculated on the "wing" boundary, as we can see on "wingMotion2D_pimpleFoam/pointDisplacement":

dimensions      [0 1 0 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    wing
    {
        type            calculated;
        value           uniform (0 0 0);
    }
...

But in the "rotorDisk" case, I think the disk which I want to apply a displacement is not a boundary. It is the objects defined on "constant/triSurface": "fixed.obj", and "rotatingZone.obj".

As we can see, the boundary conditions for the "rotorDisk" case are, for example "0/U":

Uinlet          (0 1 0);

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

internalField   uniform $Uinlet;

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform $Uinlet;
    }

    outlet
    {
        type            pressureInletOutletVelocity;
        value           uniform $Uinlet;
    }

    "slip.*"
    {
        type            slip;
    }

    #includeEtc "caseDicts/setConstraintTypes"
}

So, how to create a "pointDisplacement" file that imposes a motion to the disk (fixed.obj and rotatingZone.obj), which is not a boundary field?

Thanks

[4lix]

Hi DanFO,


Did you find a way to move your actuator disk up and down ?
I am very interesting to hear about your solution.


I am working on ship self propulsion and I want to connect the actuator disk to the ship so that they can move together.


Thanks in advance for your time and consideration!


Best regards,


Alix

[Talayal]

Hi Alix,


Were you able to do it? I am looking for the answer to the same problem..

Originally Posted by 4lix

Hi DanFO,


Did you find a way to move your actuator disk up and down ?
I am very interesting to hear about your solution.


I am working on ship self propulsion and I want to connect the actuator disk to the ship so that they can move together.


Thanks in advance for your time and consideration!


Best regards,


Alix

[4lix]

Hi Talay,


I was not able to do it.

Here is an answer from Herpes to the same question that may help you: boatAndPropeller tutorial with actuator disk


Let me know if you find something else!


Best regards,


Alix

[Talayal]

Hi Alix,

Thanks for the reply. Actually, in the mean time I was able to capture the motion of the disk with a trick. I couldn't figure out how to move the disk so I increased the innerdistance parameter for the hull in dynamicmeshdict. Since the disk is close to the hull (closer than the innerdistance value), it is moving with it. You can find the description of the parameter below;

https://openfoamwiki.net/index.php/P...Outer_Distance