Urgent Help Needed!!! (regarding FLUENT UDF)

dsen · April 27, 2010, 22:21

Hi

I am a student in Virginia. I am really struggling with a simulation, and would request any help!!
Thanks in advance.

I am simulating a 2D problem. In my rectangular domain, I have a fluid. I need to move a heat flux along a straight line in the domain. Due to this heat flux, the temperature of the fluid will change, and I will get my desired temp profile. Please note, that the heat flux is constant with time, but NOT with position - i.e. heat flux = q = C*exp(-(x^2 + y^2)), where C is any numerical constant.

I tried using F_CENTROID to get the position, but the problem is which macro to use to define the heat flux. with DEFINE_PROFILE I can give such profiles at the boundaries(walls), but how do I give this heat flux in the medium???

PLEASE HELP!
looking for assistance in how to set up problem, and how to write the UDF!!!

Thanks
DSen

gurupalani · May 27, 2010, 04:41

Hi Dsen,
Just saw your thread. So, what happened with your simulations? Have you solved it?

You need to use DEFINE_PROFILE macro itself. I don't think any other macro will do the trick. I didn't completely understand your domain. Can you elaborate a little bit?

Palani.

Allan Walsh · May 28, 2010, 13:36

Unless you really want to learn how to write UDF's, I would recommend that you take another approach. For a beginner, just to set-up your computer to run a simple UDF, and then implement it, without a lot of testing, you should probably budget at least a week.
A simpler method would be to designate a separate fluid zone in your domain to represent the straight line with the heat flux. (Yes, the zone would have some finite thickness, but modeling is all about discretizing things that are continuous). Actually, the fluid zone representing the straight line would have many separate sub-zones and you can go in in Fluent and set the heat flux (or heat generation) in each of the subzones according to your heat flux formula. Good Luck.

April 27, 2010, 22:21	Urgent Help Needed!!! (regarding FLUENT UDF)	#1
dsen New Member Deb Join Date: Apr 2010 Posts: 1 Rep Power: 0	Hi I am a student in Virginia. I am really struggling with a simulation, and would request any help!! Thanks in advance. I am simulating a 2D problem. In my rectangular domain, I have a fluid. I need to move a heat flux along a straight line in the domain. Due to this heat flux, the temperature of the fluid will change, and I will get my desired temp profile. Please note, that the heat flux is constant with time, but NOT with position - i.e. heat flux = q = C*exp(-(x^2 + y^2)), where C is any numerical constant. I tried using F_CENTROID to get the position, but the problem is which macro to use to define the heat flux. with DEFINE_PROFILE I can give such profiles at the boundaries(walls), but how do I give this heat flux in the medium??? PLEASE HELP! looking for assistance in how to set up problem, and how to write the UDF!!! Thanks DSen

May 27, 2010, 04:41	Have you solved it??	#2
gurupalani New Member C Palani Kumar Join Date: Nov 2009 Posts: 4 Rep Power: 16	Hi Dsen, Just saw your thread. So, what happened with your simulations? Have you solved it? You need to use DEFINE_PROFILE macro itself. I don't think any other macro will do the trick. I didn't completely understand your domain. Can you elaborate a little bit? Palani.

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May 28, 2010, 13:36		#3
Allan Walsh Member Allan Walsh Join Date: Mar 2009 Posts: 56 Rep Power: 17	Unless you really want to learn how to write UDF's, I would recommend that you take another approach. For a beginner, just to set-up your computer to run a simple UDF, and then implement it, without a lot of testing, you should probably budget at least a week. A simpler method would be to designate a separate fluid zone in your domain to represent the straight line with the heat flux. (Yes, the zone would have some finite thickness, but modeling is all about discretizing things that are continuous). Actually, the fluid zone representing the straight line would have many separate sub-zones and you can go in in Fluent and set the heat flux (or heat generation) in each of the subzones according to your heat flux formula. Good Luck.