[Iggy_LR]

Hello everyone,

im currently trying to implement a UDF for the movement of an ultrasonic horn. So the horn should oscillate along the z-axis. I got this UDF

DEFINE_CG_MOTION(sonotroda,dt,vel,omega,time,dtime )
{
Thread *t;
face_t f; /* define the variables */

t = DT_THREAD(dt); /* get the thread pointer for which the motion is defined */

/* if (!Data_Valid_P())
/* return; /* check if the values of the variables are accessible before you compute the function */

begin_f_loop(f,t) /* loop over each face in the zone to create an array of data */
{
if (time <= 1)
vel[1] = -2* 3.14159 * 20000 * 0.000025 * cos (2 * 3.14159 * 20000 * time); /* define the velocity of the moving zone---*/
else
vel[1] = 0;
}
end_f_loop(f,t)
}

ok when i define which face should move and preview the motion it just looks as if the zylinder elongates a long way and it doesnt look as if it oscillates around its original position. Is that normal or is there something that i did completely wrong? I uploaded a screenshot of it.

Kind regards,
Christian

[Iggy_LR]

Is there any Problem with my UDF? Is it theoretically applicable to the case that i described? -> oscillating since its a sonotrode.

Also with this Simulation Cavitation through ultrasound should be simulated.

Any help would be of great help.

Kind Regards,
Christian

[`e`]

You've applied a sinusoidal motion in the y-direction for the first second of simulation on a particular face. If you've applied this motion to one end of your cylinder then I'd expect this cylinder to elongate. Apply this motion to both end faces to create an oscillatory motion of the cylinder along the y-axis. Is the entire domain a cylinder or are there other sections?

[Iggy_LR]

Hello and thanks for your answer `e`,

i already found out today what the problem was. When i set the timestep to xe-6 or even lower then the domain that should moved in this wave pattern moved as it was intended to do. It seems that for bigger time steps the motion gets registered in a weird way and thus the cylinder elongates endlessly.

so the solution was just to decrese the timestep to sth xe-6.

xe-5 was already to big again and it already started to elongate.

Also since the moving face is a sonotrode in my case it wouldnt make sense to set both faces to move. but still thank you so much for your answer and have a nice weekend