CFD Online Discussion Forums - Using fvOptions with interFoam in a rotating framework

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Using fvOptions with interFoam in a rotating framework

Dear FOAMers:
I am having difficulties applying the fvOptions file (new to OpenFOAM 2.2) to do interFoam calculations in a rotating framework.

To get a better understanding, I created a minimum working example (MWE), where I defined a graduated cylinder (100 mm tall x 20 mm radius) using axisymmetry with the centerline following the y-axis. The cylinder is filled 50 mm with water and open to atmosphere on top as shown in the first image (plot of alpha1 variable). I then rotate the cylinder about the axis of symmetry and would expect the water level to rise on the side, but lower in the middle. However, I seem to get no response. In the second image, I should see a rise in pressure at the right side wall. Also attached is the case directory.

Attachment 20819 Attachment 20820 Attachment 20821

Questions:
Q1. Am I defining the cellzones correctly in blockMeshDict (first in blocks statement and 2nd in boundary statement)? Example:

Code:

blocks

(

    hex (   0   2   4   1   0   3   5   1) rotor (  10  50   1) simpleGrading (1 1 1)

);

boundary

(

    wall

    {

        type wall rotor;

        faces

        (

            ( 0 2 3 0 )  // Bottom

            ( 2 4 5 3 )  // Right

        );

    }

    atmosphere

    {

        type patch rotor;

        faces

        (

            ( 1 1 5 4 ) // Top

        );

    }

...

Q2. Am I correctly assuming the fvOptions is the way to add Coriolis and Centrifugal force terms to my momentum equation. Keep in mind that in my actual problem both play a role. Am I correctly describing this?

Code:

MRF1

{

    type            MRFSource;

    active          true;

    selectionMode   cellZone;

    cellZone        rotor;



    MRFSourceCoeffs

    {

        nonRotatingPatches ();

        origin      (0 0 0);

        axis        (0 1 0);

        omega       constant 50;

    }

}

Q3. Is the variable omega the rotational speed in rad/s? If so, then I have about 5 g's at the right wall, so I should definitely see something.

Thank you for your support,
Bill

Hi Bill,

If you are in a hurry, a work around would be using interDymFoam with rotating the cylinder instead of the framework, might be interesting for comparison to the new fvOptions approach. Of course, computational costs are higher.

Hello Albrecht
It turns out if I let the simulation run longer (endTime = 20 s) I do get a rise in pressure and water begins to climb up the right wall. A look at the velocities shows that they are very slowly catching up to the wall velocity. Additionally the wall velocities at the first time step took on the value (0 0 -1) = r * omega in the -z direction, which tells me the setup and behavior are correct. It happened to respond much slower than I originally guessed.

Thank you for the suggestion, though. I may be able to apply what I learned from the testTubeMixer tutorial.

Kind regards,
Bill

Looks like you simulated the quite classical Ekman spin-up time problem. :)
A quite good description can be found on this link.
http://go.owu.edu/~physics/StudentRe...asto/home.html

BR
Olle