UDF code not working

new_cfd · May 3, 2018, 04:11

Hi,
I used the following code to increase the heat flux along a vertical wall from 0-500 linearly. However it doesn't work. I checked the wall heat flux at different locations in the CFD post, but it didn't give the right fluxes.Please let me know the correct solution.

DEFINE_PROFILE(lin_incr,t,i)
{
face_t f;
float x[ND_ND];
begin_f_loop(f,t)
{
F_CENTROID(x,f,t);
F_PROFILE(f,t,i)=0+1250*x[0];
}
end_f_loop(f,t)
}

pakk · May 3, 2018, 07:08

Which fluxes did it give, and which fluxes are the "right fluxes"?

new_cfd · May 3, 2018, 09:41

It gave a uniform flux of 125 W/m2. It should increase from 0 to 500.

pakk · May 3, 2018, 10:55

Does your boundary happen to be located at x=0.1 m?

What is probably happening: you wrote a UDF that varies linearly in x-coordinate, but your boundary varies in y-coordinate. (Or z-coordinate?)

Use x[1] in stead of x[0] if you want to vary in y-coordinate. (Or x[2] for z-coordinate.)

new_cfd · May 3, 2018, 21:22

Yes! It works! Thanks a lot!

May 3, 2018, 04:11	UDF code not working	#1
new_cfd New Member newuser Join Date: Dec 2017 Posts: 11 Rep Power: 8	Hi, I used the following code to increase the heat flux along a vertical wall from 0-500 linearly. However it doesn't work. I checked the wall heat flux at different locations in the CFD post, but it didn't give the right fluxes.Please let me know the correct solution. DEFINE_PROFILE(lin_incr,t,i) { face_t f; float x[ND_ND]; begin_f_loop(f,t) { F_CENTROID(x,f,t); F_PROFILE(f,t,i)=0+1250*x[0]; } end_f_loop(f,t) }

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May 3, 2018, 07:08		#2
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 27	Which fluxes did it give, and which fluxes are the "right fluxes"?

May 3, 2018, 09:41		#3
new_cfd New Member newuser Join Date: Dec 2017 Posts: 11 Rep Power: 8	It gave a uniform flux of 125 W/m2. It should increase from 0 to 500.

May 3, 2018, 10:55		#4
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 27	Does your boundary happen to be located at x=0.1 m? What is probably happening: you wrote a UDF that varies linearly in x-coordinate, but your boundary varies in y-coordinate. (Or z-coordinate?) Use x[1] in stead of x[0] if you want to vary in y-coordinate. (Or x[2] for z-coordinate.)

May 3, 2018, 21:22		#5
new_cfd New Member newuser Join Date: Dec 2017 Posts: 11 Rep Power: 8	Yes! It works! Thanks a lot!