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-   -   incorrect cg motion UDF sdof_properties::libudf on zone 6 (assuming no motion) (http://www.cfd-online.com/Forums/fluent-udf/115040-incorrect-cg-motion-udf-sdof_properties-libudf-zone-6-assuming-no-motion.html)

M.Magdy March 22, 2013 07:58

incorrect cg motion UDF sdof_properties::libudf on zone 6 (assuming no motion)
 
Hi,
I'm trying to simulate the movement of floating body in sea.
I'm using a udf for wall movement :
#include "udf.h"
DEFINE_CG_MOTION(wave, dt, cg_vel, cg_omega, time, dtime)
{
cg_vel[0] = ((4)*(sin((63)*(time))));
cg_vel[1] = 0.0;
cg_vel[2] = 0.0;

cg_omega[0] = 0.0;
cg_omega[1] = 0.0;
cg_omega[2] = 0.0;

}


and another one for the floating body six_dof_property:

/************************************************** *****
SDOF property compiled UDF with external forces/moments
************************************************** *****/
#include "udf.h"

DEFINE_SDOF_PROPERTIES(sdof_properties, prop, dt, time, dtime)
{
prop[SDOF_MASS] = 85167.33;
prop[SDOF_IXX] = 174112.84;
prop[SDOF_IYY] = 28237716.54;
prop[SDOF_IZZ] = 28237716.54;

prop[SDOF_ZERO_TRANS_X] = TRUE;
prop[SDOF_ZERO_TRANS_Y] = TRUE;
prop[SDOF_ZERO_ROT_Z] = TRUE;
printf ("\n updated 6DOF properties");
}

when i check the "six DOF" option in dynamic mesh the wall doesn't move and this message appears:
Unable to read motion history

while if i unchecked it an error appears -
but the waves are generated correctly-:
incorrect cg motion UDF sdof_properties::libudf on zone 6 (assuming no motion)

So if anyone could tell me whether I should -in my case- check the box beside "six DOF" in dynamic mesh options or not.
knowing that :
  • when i check it -----------> no waves are generated (the wall doesn't move)
  • when i uncheck it ---------> waves are generated but the floating body make no motion

Thanks.


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