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-   -   Modeling shaking motion Vs Rotational motion (http://www.cfd-online.com/Forums/openfoam-solving/59556-modeling-shaking-motion-vs-rotational-motion.html)

 jaswi July 17, 2007 15:02

Dear OpenFoam users While s

Dear OpenFoam users

While searching for the rotational motion of single frame I have found enough support and explanation. For the rotation one adds terms corresponding to the Coriolis force and the Centripetal Force

volVectorField Fcent = (Omega ^ (Omega ^ mesh.C()));

tmp<fvvectormatrix> UEqn
(
fvm::div(phi, U)
+ turbulence->divR(U)
+ (2*Omega ^ U)
+ Fcent
);
------------------------------------------
In the above case, all the cell centres follow a circular trajectory.

My question is regarding the shaking motion. The object is placed on a platform which shakes with a given frequency and amplitude. I have attached a sketch for clarity. As can be seen from the sketch , a point on the circumference of the object doesn't follows a circular trajectory.
I guess the term:

volVectorField Fcent = (Omega ^ (Omega ^ mesh.C()));

has to be changed as messh.C() varies and depends on the angle of rotation.
Does any body have a clue how the Fcent has to be modified to properly model such kind of behaviour.

With best Regards
Jaswinder

http://www.cfd-online.com/OpenFOAM_D...ges/1/4937.jpg

 hsieh July 19, 2007 10:23

Hi, Jaswinder, Yes, I looke

Hi, Jaswinder,

Yes, I looked into this type of motion before. Basically, you have to decompose force in X-direction and in Y-Direction (assuming a 2D case in X-Y). Based on omega, you should know the position of the object, i.e., (x, y) as a function of time. Then, do two derivatives to computation acceleration, then, multipy by mass to get Force as function of time.

Pei

 jaswi July 19, 2007 22:44

Thanks Pei Shall give it a

Thanks Pei

Shall give it a try.

Regards
Jaswinder

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