# non-uniform inlet velocity simulation in Fluent 13.0

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 October 24, 2013, 21:04 non-uniform inlet velocity simulation in Fluent 13.0 #1 New Member   shuminhua Join Date: Aug 2009 Posts: 3 Rep Power: 9 Sponsored Links The performance of propeller is computing in Fluent 13.0. The inlet velocity which is non-uniform inflow was given using UDF in fluent. When I use turbulence model to simulate, the inlet velocity dissipated quickly (The plane close to the inlet whose velocity like the uniform). When I use Laminar or Inviscid model to simulate, there is no dissipation (the outlet velocity is similar to the inlet velocity) Can someone give me a hint on how to do that ? Thanks for your help !

October 25, 2013, 02:36
#2
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Astio Lamar
Join Date: May 2012
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"The inlet velocity which is non-uniform inflow was given using UDF in fluent."

for this you should compile a UDF to impose a velocity profile through the inlet. or you need to use points!
For UDF you need to fit a polyline to the inlet profile velocity and then impose this polyline.

here is an example of the velocity profile UDF:

Quote:
 #include "udf.h" DEFINE_PROFILE(inlet_velocity, thread, position) { real z[ND_ND]; /* this will hold the position vector */ real y; face_t f; begin_f_loop(f, thread) { F_CENTROID(z,f,thread); y = z[1]; F_PROFILE(f, thread, position) = 0.3-0.4*y+0.6*y*y; } end_f_loop(f, thread) }

the red equation is the mentioned polyline.

 October 27, 2013, 20:17 #3 New Member   shuminhua Join Date: Aug 2009 Posts: 3 Rep Power: 9 Thanks and sorry for my poor English. In my case, I give the UDF in fluent and the inlet velocity shows from the velocity contours which seems to be no problem. I use Inviscid and Laminar model (Viscous model) to simulate,the velocity of the sections parallel to the inlet are similar to the inlet velocity(the inlet velocity are non-uniform). But when i change viscous model to two equation turbulence model (SST , RNG)，the velocity of the sections parallel to the inlet which are fully uniform(the dissipation are very quick). thanks

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