Hi Sujith

Thank you for your response. I have spent a long time on finding the example and method of how to using the concentration micros-- C_STORAGE_R(c,t,SV_DPMS_CONCENTRATION). But I haven`t find no help document of UDF.I think I should know the usage of this micros and its means. Can you help me for giving an example or relative help document. Thank you so much! #include "udf.h" #include "dpm.h" #include "surf.h" #define C1 0.0029 #define C2 0.03232 DEFINE_DPM_BODY_FORCE(p_b_force,p,i) { real bforce; cell_t c = RP_CELL(&(p->cCell)); Thread *t = RP_THREAD(&(p->cCell)); if(i==1) bforce=0; else if(i==0) bforce=C1*P_POS(p)[0]*P_POS(p)[0]* C_STORAGE_R(c,t,SV_DPMS_CONCENTRATION)+C2*P_POS(p)[0]; ???? return (bforce/P_MASS(p)); }

I am not sure where this is the exact usage...

you can define a variable and store dpm conc and then use it ------- ------ DEFINE_DPM_BODY_FORCE(p_b_force,p,i) { real conc; cell_t c = RP_CELL(&(p->cCell)); Thread *t = RP_THREAD(&(p->cCell));

conc = C_STORAGE_R(c,t,SV_DPMS_CONCENTRATION);

bforce= f(conc,x,y); return bforce/pmass; } ---

are you getting any error when using this way?