[ali_bizhanpour]

Hi all
I trying to use Six DOF UDF with one DOF rotation for simulating a moving guide vine in a water pipe with a diameter of 0.1 meter and I set mass flow rate equal to 11 kg/s for inlet boundary condition. I face this error every time.

Error: Update-Dynamic-Mesh failed. Negative cell volume detected.
Error Object: #f


I tried different time steps, even less than 1e-6 but the problem was not solved.

this is my UDF :

#include "udf.h"
DEFINE_SDOF_PROPERTIES(blade, sdof_prop, dt, time, dtime)
{
Six_DOF_Object *sdof_obj = NULL;
sdof_prop[SDOF_MASS] = 0.053;
sdof_prop[SDOF_IXX] =2.2e-6;
sdof_prop[SDOF_IYY] = 4e-6;
sdof_prop[SDOF_IZZ] =5.5e-6;
sdof_prop[SDOF_LOAD_M_X] = 0.0;
sdof_prop[SDOF_LOAD_M_Y] = 0.0;
sdof_prop[SDOF_LOAD_M_Z] = 0.0;

sdof_prop[SDOF_SYMMETRY_X] = 0; /* normal vector of symmetry plane for half model */
sdof_prop[SDOF_SYMMETRY_Y] = 1 ;/* normal vector of symmetry plane for half model */
sdof_prop[SDOF_SYMMETRY_Y] = 0 ; /* normal vector of symmetry plane for half model */

sdof_obj = Get_SDOF_Object(DT_PU_NAME(dt));
if (NULLP(sdof_obj))
{
/* Allocate_SDOF_Object must be called with the same name as the udf */
sdof_obj = Allocate_SDOF_Object(DT_PU_NAME(dt));
SDOFO_1DOF_T_P(sdof_obj) = FALSE; /* one DOF translation */
SDOFO_1DOF_R_P(sdof_obj) = TRUE; /* one DOF rotation */
SDOFO_DIR(sdof_obj)[0] = 0.0;
SDOFO_DIR(sdof_obj)[1] = 1.0;
SDOFO_DIR(sdof_obj)[2] = 0.0;
SDOFO_CENTER_ROT(sdof_obj)[0] = 0.09354; /* only needed for one DOF rotation */
SDOFO_CENTER_ROT(sdof_obj)[1] = 0.0; /* only needed for one DOF rotation */
SDOFO_CENTER_ROT(sdof_obj)[2] = -0.01; /* only needed for one DOF rotation */
SDOFO_CONS_P(sdof_obj) = TRUE; /* constrained */
if (SDOFO_CONS_P(sdof_obj))
{
SDOFO_LOC(sdof_obj) = 0.0;
SDOFO_MIN(sdof_obj) = -0.1745;
SDOFO_MAX(sdof_obj) = 0.1745;
SDOFO_F(sdof_obj) = 0.0; /* spring preload */
SDOFO_K(sdof_obj) = 2.76; /* spring constant */
SDOFO_INIT(sdof_obj) = SDOFO_LOC(sdof_obj);
SDOFO_LOC_N(sdof_obj) = SDOFO_LOC(sdof_obj);
}
}
}

these are my dynamic mesh setting:
remeshing.PNG

s.PNG

1.PNG