Hi, I have a big problem, I have to calculate drag force on a sphere in a duct using ansys 10, but intsrf, tauw result 0...so I cannot calculate it. code is the following...someone help me!! Please

/NOPR ! Suppress printing of UNDO process /PMACRO ! Echo following commands to log FINISH ! Make sure we are at BEGIN level /CLEAR,NOSTART ! Clear model since no SAVE found ! WE SUGGEST YOU REMOVE THIS LINE AND THE FOLLOWING STARTUP LINES /input,start100,ans,'C:\Archivos de programa\Ansys Inc\v100\ANSYS\apdl\',,,,,,,,,,,,,,,,1 /REPLOT,RESIZE

/NOPR

/PMETH,OFF,0 /FILNAME,2d_sim,0 KEYW,PR_CFD,1

!units in micron

/units,si,10^-6 /PREP7 nts = 40 ! number of time steps time =2 ! total simulation time delta = time/nts RHO = 1000 ! Fluid density MU = 0.001 ! Fluid viscosity

ET,1,FLUID141

RECTNG,-700,-25,1,50 RECTNG,-25,25,1,50 RECTNG,25,700,1,50 RECTNG,-25,25,0,1 CYL4,0,0.5,0.1, asba,4,5

aglue,all alls

!meshing

lsel,s,,,1,3,2 lesize,all,1,,,1 alls lsel,s,,,2,4,2 lesize,all,1,,,-4 alls amesh,1

lsel,s,,,21,22 lesize,all,1,,,1 alls lsel,s,,,2,6,4 lesize,all,1,,,-4 alls amesh,4 alls

lsel,s,,,23,24 lesize,all,1,,,1 alls lsel,s,,,6,10,4 lesize,all,1,,,-4 alls amesh,5

SMRT,1 MSHAPE,1,2D MSHKEY,0 amesh,7

AREFINE,7, , ,1,0,1,1

!boundary conditions

DL,10, ,PRES,0,1

DL,1, ,VY,0,1

DL,3, ,VY,0,1

DL,22, ,VY,0,1

DL,24, ,VY,0,1

DL,23, ,VY,0,1

DL,26, ,VY,0,1

DL,13, ,VY,0,1

DL,25, ,VY,0,1

DL,4, ,vx,0.031e-3

/SOL

/del,2d_sim,rfl FLDATA1,SOLU,TRAN,1 FLDATA1,SOLU,FLOW,1 FLDATA1,SOLU,TURB,1 FLDATA1,SOLU,RDSF,1 FLDATA7,PROT,DENS,CONSTANT FLDATA8,NOMI,DENS,RHO, FLDATA7,PROT,VISC,CONSTANT FLDATA8,NOMI,VISC,MU FLDATA12,PROP,IVIS FLDATA7,PROT,COND,CONSTANT FLDATA8,NOMI,COND,-1, FLDATA7,PROT,SPHT,CONSTANT FLDATA8,NOMI,SPHT,-1, FLDATA5,OUTP,PTOT,1 FLDATA5,OUTP,STRM,1 FLDATA5,OUTP,TAUW,1 flda,time,step,delta flda,time,numb,nts flda,time,tend,time

solve

/POST1 SET,LAST PLVECT,V, , , ,VECT,ELEM,ON,0

!calculo promedio velocidad

lsel,s,,,17,20,1 lplot nsll,s,1 nplot

!average velocity

vel_x=0 vel_y=0

*get,n_nod,node,0,count *dim,velo_nod,table,n_nod,3 *do,_l,1,n_nod,1

*get,pnn,node,0,num,min

*set,velo_nod(_l,0),pnn

*GET,velo_nod(_l,1),NODE,pnn,V,X

*GET,xxx,NODE,pnn,V,X

vel_x=vel_x+xxx

*GET,velo_nod(_l,2),NODE,pnn,V,y

*GET,yyy,NODE,pnn,V,y

vel_y=vel_y+yyy

*GET,velo_nod(_l,3),NODE,pnn,v,sum

nsel,u,node,,pnn,pnn,1

*ENDDO vel_x=vel_x/n_nod vel_y=vel_y/n_nod

alls

!average velocity to calcule drag force

LOCAL,11,0,-0.1,0.5,0, , , ,1,1, CSYS,11,

intsrf,tauw

*get,forcex,intsrf,0,item,fx *get,forcey,intsrf,0,item,fy *get,forcez,intsrf,0,item,fz *get,momx,intsrf,0,item,mx *get,momy,intsrf,0,item,my *get,momz,intsrf,0,item,mz

!!I'd like to know drag force on sphere..result is 0!!

well I have to admit, I cannot really follow your script (and I guess it's not about the script itself, I just do not understand it) but the typical problem (no offense) is to try to get the drag all over the surface, not only in the projection of the plane perpendicular to the flow direction IN ONE direction.

just a guess.

matej