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Issues with UDF for ball movement inside a valve

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Old   July 29, 2015, 14:04
Red face Issues with UDF for ball movement inside a valve
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Ahmed Jalal
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Hello All,

I am trying to simulate motion of a ball in a valve. The model I created is a simple 2D half model of the cross-section of a hypothetical valve. There is an attachment of the model.

I have created a UDF file to define motion of the ball due to velocity using the 6DOF solver. The symmetry line should also be deforming. I have a few questions.

1) Do I need to run a case without any Dynamic Mesh before compiling the code?

2) I keep getting an error that says: Unable to read motion history file

3) Can you please let me know if there are any suggestions to make to the UDF.

Here is the UDF for the motion:

#include "udf.h"

DEFINE_SDOF_PROPERTIES(Lightweight_ball, prop, dt, time,dtime)

{

prop[SDOF_ZERO_TRANS_X]= TRUE;
prop[SDOF_ZERO_TRANS_Z]= TRUE;

prop[SDOF_ZERO_ROT_X]= TRUE;
prop[SDOF_ZERO_ROT_Y]= TRUE;
prop[SDOF_ZERO_ROT_Z]= TRUE;


prop[SDOF_MASS] = 1e-3;


prop[SDOF_IXX] = 1.92e-8;
prop[SDOF_IYY] = 1.92e-8;
prop[SDOF_IZZ] = 1.92e-8;

}


And someone suggested I do a changing time step UDF as well:

#include "udf.h"
#include "dx.h"
#include "grid.h"
#include "var.h"
#include "mem.h"
#include "dynamesh_tools.h"


DEFINE_DELTAT(mydeltat,d)
{
int z_ID =5;
real urf = 0.5;
real mydx=1e-5;
real maxT= 1e-3;
real minT= 1e-10;

real time_step;
real my_vel;
real TS1;

Dynamic_Thread *ndt = NULL;

Thread *ball_ft = Lookup_Thread(d,z_ID);
ndt = THREAD_DT(ball_ft);

my_vel = DT_VEL_CG(ndt)[1];

TS1 = ABS(urf*mydx/(my_vel+0.00000001));
//Message("\n My TS1 %f",TS1);

time_step = MIN(TS1,maxT);
//Message("\n My Time Step1 %f",time_step);

time_step = MAX( time_step, minT);
Message("\n My Time Step %f",time_step);

return time_step;
}


Thanks
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Old   July 30, 2015, 01:11
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maybe it doesn't save the backup/results/convergence plot files, but no idea, how to make it do it.
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6dof, dynamic mesh, mesh motion, udf, valve

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