Hello all, I desperately need your help with the UDF. 1) Can C_VOLUME return value correctly? To calculate the sum of cell volume adjoin to one certain boundary surface, I use the following program. ID=8 is the no. found in the BC panel. However the reported results is 6.6e-5, which is far from the data (1.5521334e-06) obtained through the "report/surface integral/ sum". Could somebody tell me the reason? Domain *d; Thread *t,*ct; face_t f; cell_t c; int ID=8; d=Get_Domain(1); t=Lookup_Thread(d, ID); ct=THREAD_T0(t); begin_c_loop(c, ct)

{sumvolume+= C_VOLUME(c,ct);} end_c_loop(c, ct) 2) May I know whether the Lookup_Thread(domain,zone_ID)can return cell thread? I try to use it as cell thread for looping all the cells in one certain boundary surface. But it fails. 3) I also want to do something for one type of boundary surfaces, so I use if (THREAD_TYPE(ft) == THREAD_F_WALL) to judge whether the face thread is pointed to the right type of boundary faces. But it fails. 4) Can I retrieve Thread associated with an interior surface at specific location and how to do it? Your kindly help will be greatly appreciated!

ID=8; t=Lookup_Thread(d, ID);

begin_f_loop(f,t) { sumvolume+= C_VOLUME(F_C0(f,t),t->t0); } end_f_loop(f,t)

Message(" volume %e\n ",sumvolume);

Hi, saghir, Thank you very much for your advice. I try to use your code, but the compiler of FLuent shows the following information: structure reference not implemented for line 21, where it is the code of sumvolume+= C_VOLUME(F_C0(f,t),t->t0); If convenient, could you give me further advice on it? Thanks a lot! By the way, may I know the meaning of F_C0(f,t) and t->t0? I check the help documents, but could not find it. Thank you very much for your time and efforts!

I tested the first program, it works very well if not use that there:

ID=8; t=Lookup_Thread(d, ID); Thread *t0 = THREAD_T0(t);

begin_f_loop(f,t) {

cell c0 = F_C0(f,t); sumvolume+= C_VOLUME(c0,t0); } end_f_loop(f,t)

Message(" volume %e\n ",sumvolume);

Hi, Saghir, Thank you very much for your effort! May I know the meaning of cell c0=F_C0(f,t)? I try to run it in FLUENT. Although it can be compiled sucessfully, there is an error message as following. Error: Chip: internal error: invalid builtin -1: pc=136. Thanks a lot!

c0=F_C0(f,t) adjacent cell for the face f

Thanks a lot for your kindly help! Your advice is really useful. By the way, do you know whether we can initialize the arrays in UDF as zero? I try to initilize the array PA[3][60] using the following senternse: for (i=0;i<3;i++) {for (j=0;j<60;j++)

{PA[i][j]=0.0;}} But it fails. Would you please give me some advices on it? Thanks a million!