2 inlets, 2 UDF

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 July 13, 2010, 05:28 2 inlets, 2 UDF #1 New Member   bilalmerei Join Date: Mar 2010 Posts: 14 Rep Power: 9 Sponsored Links plz i need an urgent help. i have to inject oil into water. the problem that water must have a specific profile of velocity so i have to introduce a UDF. and same for the oil. so i don't know how to define 2 UDF and interpret them in each inlet. plz help

 December 12, 2010, 14:26 UDF needed too #2 New Member   Rajat Join Date: Dec 2010 Posts: 2 Rep Power: 0 I too need udf function for a fully developed velocity profile at inlet in vertical channel . As i have never worked on Fluent i dont know how udf have to write is it exactly the same code as in FORTRAN or C as i know both well but udf i dont know

 December 12, 2010, 14:54 #3 Senior Member   Real Name :) Join Date: Jan 2010 Location: United States Posts: 192 Rep Power: 9 UDF's are User Defined Functions They are typically written in C, but can be written in Fortran. Fluent has a C interpreter built in, so you don't need one unless aspects of the calculation (specific Fluent calls, speed of calculation, etc) require compilation. To impose a fully developed profile at a wall, you must loop over all faces of the wall and set the velocity magnitude (or, perhaps, a vector component) equal to the velocity you obtain from fully developed flow. In the code below, I assume the following: 1) Fully developed laminar flow 2) 2-D flow in the x-direction 3) An inlet face which extends from 0.5 to -0.5 in the y-direction 4) A maximum centerline velocity of 10 Code: ```#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) = 10.-10.*(y*y/(0.5*0.5)); } end_f_loop(f, thread) }``` I haven't tested it, but it should function OK with few, if any, changes. I don't know which direction you've specified as vertical, so you'll need to adapt a few things in the code above to fit your application. Go here: http://combust.hit.edu.cn:8080/fluen.../udf/node2.htm for more information on UDFs. ComputerGuy

 December 13, 2010, 03:04 Thanks #4 New Member   Rajat Join Date: Dec 2010 Posts: 2 Rep Power: 0 many thanks to ComputerGuy for you help and code I will try to learn and do whatever is needed furthermore.

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