# Modeling shaking motion Vs Rotational motion

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 July 17, 2007, 15:02 Dear OpenFoam users While s #1 Senior Member   Join Date: Mar 2009 Posts: 248 Rep Power: 9 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 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

 July 19, 2007, 10:23 Hi, Jaswinder, Yes, I looke #2 Senior Member   Pei-Ying Hsieh Join Date: Mar 2009 Posts: 317 Rep Power: 9 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

 July 19, 2007, 22:44 Thanks Pei Shall give it a #3 Senior Member   Join Date: Mar 2009 Posts: 248 Rep Power: 9 Thanks Pei Shall give it a try. Regards Jaswinder

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