Fluent UDF

nasir.iitd · February 17, 2015, 05:56

Hello friends,
I want to write udf for rms tangential velocity of a flow through pipe and have no primary knowledge about how to write udf. Though fluent has default way to calculate y-rms velocity but this is not coming correct in my case. That is why I want write UDF code for it. Need help.

pakk · February 17, 2015, 08:34

Show us your attempts, and we will tell what to improve. That is the best way to learn it.

nasir.iitd · February 18, 2015, 04:21

Hello pakk,
Thanks for your response.
I'm running LES in Ansys 15.0 fluent for studying turbulence of rotating pipe flow. Rotating pipe flow behaves as solid body rotation.Domain is a circular pipe. While plotting RMS profile of y-velocity(tangential), it is showing negative values. How is it possible? RMS negative?? It seems that software is not calculating y-rms quantity because magnitude of y-rms and y-mean velocities are almost looking same.
The following parameters are set:
1. Cell zone condition: Frame motion>Rotational axis-Z>Rotational speed in rad/s;
2. Velocity inlet: Vel.specification method=components>Ref. Frame=Rel. to adjacent cell zone>Cord. system=cartesian>z-velocity=0.8m/s> Fluctuating algorithm=Spectral synthesizer>Turb.intensity=5%>Length scale=0.004m;
3. Wall: Moving wall> Rel. to adj. cell zone>Rotational=0 rad/s(because wall is by default rotating as wall is the integral part of frame)> shear condition=no slip;
Do you need any other information?
Nasiruddin

pakk · February 19, 2015, 04:32

If you want to make a UDF, start making a UDF. You should not care (yet) if it works or not, just write down the steps you want the computer to take.

Then show that attempt here, and we will comment on that.

marauder · February 19, 2015, 12:56

Take a simple UDF or an example in UDF manual, try to understand it and modify the code slowly to see how it works. Then try to suit to your problem if you encounter any problem post it here. It's much better that way and more people understand code than your problem!
Believe me, I had the experience and learnt it that way.

February 17, 2015, 05:56	Fluent UDF	#1
nasir.iitd Member SHEIKH NASIRUDDIN Join Date: Aug 2013 Location: DELHI Posts: 52 Rep Power: 12	Hello friends, I want to write udf for rms tangential velocity of a flow through pipe and have no primary knowledge about how to write udf. Though fluent has default way to calculate y-rms velocity but this is not coming correct in my case. That is why I want write UDF code for it. Need help.

February 18, 2015, 04:21	y-rms negative	#3
nasir.iitd Member SHEIKH NASIRUDDIN Join Date: Aug 2013 Location: DELHI Posts: 52 Rep Power: 12	Hello pakk, Thanks for your response. I'm running LES in Ansys 15.0 fluent for studying turbulence of rotating pipe flow. Rotating pipe flow behaves as solid body rotation.Domain is a circular pipe. While plotting RMS profile of y-velocity(tangential), it is showing negative values. How is it possible? RMS negative?? It seems that software is not calculating y-rms quantity because magnitude of y-rms and y-mean velocities are almost looking same. The following parameters are set: 1. Cell zone condition: Frame motion>Rotational axis-Z>Rotational speed in rad/s; 2. Velocity inlet: Vel.specification method=components>Ref. Frame=Rel. to adjacent cell zone>Cord. system=cartesian>z-velocity=0.8m/s> Fluctuating algorithm=Spectral synthesizer>Turb.intensity=5%>Length scale=0.004m; 3. Wall: Moving wall> Rel. to adj. cell zone>Rotational=0 rad/s(because wall is by default rotating as wall is the integral part of frame)> shear condition=no slip; Do you need any other information? Nasiruddin

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February 17, 2015, 08:34		#2
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	Show us your attempts, and we will tell what to improve. That is the best way to learn it.

February 19, 2015, 04:32		#4
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	If you want to make a UDF, start making a UDF. You should not care (yet) if it works or not, just write down the steps you want the computer to take. Then show that attempt here, and we will comment on that.

February 19, 2015, 12:56		#5
marauder Member Anonymous Join Date: Mar 2014 Posts: 84 Rep Power: 12	Take a simple UDF or an example in UDF manual, try to understand it and modify the code slowly to see how it works. Then try to suit to your problem if you encounter any problem post it here. It's much better that way and more people understand code than your problem! Believe me, I had the experience and learnt it that way.