Alaa Ahmed
I defined the center of rotation, but then the code didn't work. it gives me error (Error: Update-Dynamic-Mesh failed. Negative cell volume detected).nI'm monitoring the moment at the center of rotation and below is the plot for the moment with time.nthe used UDF n/*******************************************************n  Six DOF property compiled UDF with one DOF rotationn *******************************************************/n#include udf.hnDEFINE_SDOF_PROPERTIES(flap, sdof_prop, dt, time, dtime)n{ntSix_DOF_Object* sdof_obj = NULL;ntsdof_prop[SDOF_MASS] = 21.5;ntsdof_prop[SDOF_IXX] = 5.5;ntsdof_prop[SDOF_IYY] = 5.5;ntsdof_prop[SDOF_IZZ] = 5.5;ntsdof_prop[SDOF_LOAD_M_X] = 0.0;ntsdof_prop[SDOF_LOAD_M_Y] = 0.0;ntsdof_prop[SDOF_LOAD_M_Z] = 0.0;ntsdof_obj = Get_SDOF_Object(DT_PU_NAME(dt));nntif (NULLP(sdof_obj))nt{ntt/* Allocate_SDOF_Object must be called with the same name as the udf */nttsdof_obj = Allocate_SDOF_Object(DT_PU_NAME(dt));nttSDOFO_1DOF_T_P(sdof_obj) = FALSE;    /* one DOF translation */nttSDOFO_1DOF_R_P(sdof_obj) = TRUE;    /* one DOF rotation */nttSDOFO_DIR(sdof_obj)[0] = 0.0;nttSDOFO_DIR(sdof_obj)[1] = 0.0;nttSDOFO_DIR(sdof_obj)[2] = 1.0;nttSDOFO_CENTER_ROT(sdof_obj)[0] = 6.0;  /* only needed for one DOF rotation */nttSDOFO_CENTER_ROT(sdof_obj)[1] = 1.1938;  /* only needed for one DOF rotation */nttSDOFO_CENTER_ROT(sdof_obj)[2] = 0.0;  /* only needed for one DOF rotation */nttSDOFO_CONS_P(sdof_obj) = FALSE;     /* constrained */nt}n}n