# UDF parbolic inlet velocity profile for 3D Ractangular channel flow.

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 August 10, 2016, 07:32 UDF parbolic inlet velocity profile for 3D Ractangular channel flow. #1 Member   Saurav Kumar Join Date: Jul 2016 Posts: 80 Rep Power: 9 i am using fluent and i have used UDF for parabolic velocity profile for 2D case at inlet as #include "udf.h" DEFINE_PROFILE(inlet_x_velocity, thread, position) { real x[ND_ND]; /* this will hold the position vector */ real y; face_t f; begin_f_loop(f, thread) { F_CENTROID(x,f,thread); y = x[1]; F_PROFILE(f, thread, position) = 0.4382 - y*y/(0.005*0.005)*0.4382; } end_f_loop(f, thread) } now i want to use UDF for 3D case, how can i convert this for 3D case? please help me thanks in advance

 August 10, 2016, 07:49 #2 Senior Member   Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,793 Rep Power: 71 the 3D problem you wanto to study has 4 walls? In such case you must solve the elliptic equation Lap w = q on the inflow plane (w is the streamwise velocity, q depends on the pressure gradient and Re number)

August 10, 2016, 08:02
#3
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Saurav Kumar
Join Date: Jul 2016
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Quote:
 Originally Posted by FMDenaro the 3D problem you wanto to study has 4 walls? In such case you must solve the elliptic equation Lap w = q on the inflow plane (w is the streamwise velocity, q depends on the pressure gradient and Re number)
yes four wall but i just want to specify (u) normal component of velocity at inlet surface and v=w=0.

August 10, 2016, 08:05
#4
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Filippo Maria Denaro
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Quote:
 Originally Posted by srv537 yes four wall but i just want to specify (u) normal component of velocity at inlet surface and v=w=0.

I called w the streamwise component that you called u. It is the same, you must solve the 2D Poisson problem.

August 10, 2016, 09:25
#5
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Saurav Kumar
Join Date: Jul 2016
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Quote:
 Originally Posted by FMDenaro I called w the streamwise component that you called u. It is the same, you must solve the 2D Poisson problem.
actually i want to modify this code for 3D velocity profile and compile to fluent as a inlet boundary condition.
i dont know how to do this