# Constant & independent velocity for DPM particles

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 September 22, 2010, 10:03 Constant & independent velocity for DPM particles #1 Member   Roman Gobitz-Pfeifer Join Date: Dec 2009 Location: Stuttgart Posts: 76 Rep Power: 7 Hi, I'm having the following problem. After they are injected, water droplets (DPM particles) should travel through my geometry with a constant velocity, which is not effected by gravity or the surrounding fluid. Heat and mass transfer should still take place during this problem. Is it possible to write a UDF for DPM particles? Which macro fits best for this problem? I've already tried DEFINE DPM BODY FORCE without any results. The whole setup is 2D. Can anybody please help me? thanks Wikie

 September 23, 2010, 05:35 problem with exaples from the UDF GUIDE #2 Member   Roman Gobitz-Pfeifer Join Date: Dec 2009 Location: Stuttgart Posts: 76 Rep Power: 7 Hi, to get use to UDF-programming I start playing arround with the examples mentioned in the ANSYS UDF GUIDE. I copied this example: #include "udf.h" DEFINE_DPM_DRAG(particle_drag_force,Re,p) { real w, drag_force; if (Re < 0.01) { drag_force=18.0; return (drag_force); } else if (Re < 20.0) { w = log10(Re); drag_force = 18.0 + 2.367*pow(Re,0.82-0.05*w) ; return (drag_force); } else /* Note: suggested valid range 20 < Re < 260 */ { drag_force = 18.0 + 3.483*pow(Re,0.6305) ; return (drag_force); } } But it didn't work. My particles totally disappeared and I got this message. What is wrong with this code?? "chip-exec: particle_drag_force: argument 1: incorrect type (10): pointer expectedchip-exec: particle_drag_force: argument 2: incorrect type (38): int expected" cheers Wikie

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