# UDF for fan model

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 August 9, 2007, 22:27 UDF for fan model #1 zhaoh Guest   Posts: n/a Sponsored Links Dear everyone I'm making the air flow through a fan. The relationship between the pressure difference and velocity is detaP=139-12V.I want use UDF to solve the problem. #include"udf.h" DEFINE_PROFILE(pressure,t,i) { real x[ND_ND]; real y; face_t f; begin_f_loop(f,t) { F_CENTROID(x,f,t); F_PROFILE(f,t,i)=139-12*C_V(cell,thread); } end_f_loop(f,t) } But i think the udf has some problems. For example,C_V(cell,thread) has some difference with the V(in the equation),V is stand for mean-face-velocity. Scecond, detaP is pressure difference not Gause pressure.Does the F_PROFILE(f,t,i)=139-12*C_V(cell,thread) adapt for detaP=139-12V？How to amend the UDF? Hope your reply!! Thank you so much...

 February 9, 2012, 10:42 #2 Member   Yolk Join Date: Nov 2011 Posts: 38 Rep Power: 7 Dear zhaoh, have you find out the solution for your question?I also concern the F_PROFILE(f,t,i) can add pressure difference or not? Yannian

 February 19, 2012, 08:30 UDF for pressure variation #3 Member   Nirav Join Date: Jul 2011 Posts: 43 Rep Power: 8 Hii friends My problem is flow through river channel, I have taken a orbitary region so at exit of my geometry flow exits into river itself. so i need to know how to apply UDf at exit, as pressure must vary with P=row*g*h. my exit cross section is not uniform so what should i do please help. is it possible to apply custom field function ???? in fluent please help ASAP

 February 20, 2012, 04:49 #4 Member   Yolk Join Date: Nov 2011 Posts: 38 Rep Power: 7 Dear Nirav, I think your probelm can be solved by UDF.The formula in your fomular is height whose direction assumed in y direction, so you can write udf in this way(You have to modify some line for your own coordinate): #include "udf.h" DEFINE_PROFILE(Pressionaxiale, thread , position) { real z[ND_ND]; real y; face_t f; begin_f_loop(f, thread) { F_CENTROID(z,f,thread); y=z[1]; row=1000; g=9.8; P0=101325; F_PROFILE(f, thread, position) =(P0+row*g*y); } end_f_loop(f, thread) }

 February 20, 2012, 06:31 #5 Member   Nirav Join Date: Jul 2011 Posts: 43 Rep Power: 8 Thank you Yannian I will try this method

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