output the dragforce

Submitted by openfoam on Thu, 03/28/2013 - 10:20

In the DEM inpustscript file, I use the comand:
compute dragtotal all reduce sum f_dragforce[1] f_dragforce[2] f_dragforce[3]
#screen output
compute 1 all erotate/sphere
thermo_style custom step atoms ke c_1 vol c_centerOfMass[3] c_dragtotal[1] c_dragtotal[2] c_dragtotal[3]
thermo 10
thermo_modify lost ignore norm no
compute_modify thermo_temp dynamic yes
#insert the first particles so that dump is not empty
dump myDump all stl 1 ../DEM/post/dump_*.stl
#run 1
dump dmp all custom 100 ../DEM/post/dump*.meshGran id type type x y z vx vy vz fx fy fz f_dragforce[1] f_dragforce[2] f_dragforce[3] radius

to output the drag force, the screen output is:

Step Atoms KinEng 1 Volume centerOf dragtota dragtota dragtota
401 18 0.31959064 1.349667e-05 0.045144 0.19798336 367.85555 77.949508 -42889.077

but in the dump file, the drag force is :
ITEM: ATOMS id type type x y z vx vy vz fx fy fz f_dragforce[1] f_dragforce[2] f_dragforce[3] radius
6 1 1 -0.0185977 0.0180572 0.126699 1.85043 0.129289 7.91131 8.47019e-05 5.38816e-06 0.00032971 8.47019e-05 5.38816e-06 0.000330113 0.002

What's the difference between the c_dragtotal and the f_dragforce? which one is the particle's drag force?