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librasu July 2, 2006 08:55

wall shear stress
I would like to access the WALL Shear stress on the boundary faces. When I complied the UDF file to FLUENT, this line, NV_V(wallshear,=,C_STORAGE_R_NV(f,t,SV_WALL_SHEAR) );, has problem. The value of wallshear was not an array, and it was not reasonable. I hope that someone can point the problem out. The problem makes me quite confused. Thanks a lot.

#include "udf.h" #include "sg.h" #include "mem.h" #include "sg_pdf.h" #define PI 3.1415926

DEFINE_GRID_MOTION(ccc, domain, dt, time, dtime)

{ Thread *tf=DT_THREAD(dt); Thread *t; face_t f; cell_t c; Node *node_p; real Z_A,A_by_es,www,NV_VEC(WSS),AA,Z_B,area,NV_VEC(wal lshear),NV_VEC(A); int n; if (!Data_Valid_P())




begin_f_loop(f,tf) {



NV_V(wallshear,=,C_STORAGE_R_NV(f,t,SV_WALL_SHEAR) );



} end_f_loop(f,tf); }

librasu July 2, 2006 13:30

Re: wall shear stress
The UDF cannot be compiled in Windows OS, but it can be compiled in Unix O. When it is compiled in Unix, Fluent ignored the C_STORAGE_R_NV(f,t,SV_WALL_SHEAR). When in Windows, the error message:

Updating solution at time level N... done. Updating mesh at time level N... Error: FLUENT received fatal signal (ACCESS_VIOLATION) 1. Note exact events leading to error. 2. Save case/data under new name. 3. Exit program and restart to continue. 4. Report error to your distributor. Error Object: ()

I am not sure whethre the UDF can storage the WALL_SHEAR_STRESS, since the value is either more than 1 billion or 0 in windows. In Unix, the value is 0, since this commond is ignored.

I also doubt the C_STORAGE_R_NV(face, face_thread, SV_WALL_SHEAR), since the C means the cell, I think, and the the variable and the thread are belonging to face. I google the Wall Shear Stress Macro, and I also find F_STORAGE_R_N3V(f,tf,SV_WALL_SHEAR). Therefore, the expression of WSS macro is a litttle confusing.

Since I typed many words, I hope that I can get some response and the useful advices. God Bless

Thanks You So Much.

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