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 September 19, 2012, 14:44 Unsteady case #1 New Member   m.reza Join Date: Apr 2011 Posts: 18 Rep Power: 6 Hi I study on an unsteady case, my time step is equal to 0.0001 and I need to get average between Nusselt number of each time step in x direction. I have 1000 time steps in my analyzed at least. Is there a method in Fluent that I want to have a graph of time-averaged Nusselt Number distribution on the hot surface finally?

September 19, 2012, 20:40
#2
Senior Member

Syavash
Join Date: Apr 2010
Location: Tehran, Karaj
Posts: 185
Rep Power: 7
Quote:
 Originally Posted by m.reza Hi I study on an unsteady case, my time step is equal to 0.0001 and I need to get average between Nusselt number of each time step in x direction. I have 1000 time steps in my analyzed at least. Is there a method in Fluent that I want to have a graph of time-averaged Nusselt Number distribution on the hot surface finally?
Hi

I'm a little confused with your case! What do you want to obtain exactly?!
Time-Averaged mean Nusselt number of all time steps or mean Nusselt number at each time step?!!
What is the physics of your problem?! You are studying on an external or internal flow?!

 September 20, 2012, 04:56 tnx syavash #3 New Member   m.reza Join Date: Apr 2011 Posts: 18 Rep Power: 6 Dear Siavash, I study on a jet that targets to the hot surface for cooling, the profile of velocity in the jet inlet is sinusoidal, so my case is unsteady. My time step is 1e-4 and for example in the frequency of 10Hz, I have 1000 time steps only in one cycle, I have to run this case for 5 cycles. Finally I want to draw time-averaged Nusselt number on the hot surface. I have one method that I write data file of each time step and then export local Nusselt number of that time step. So I get average between nusselt numbers, and then draw time-averaged local Nusselt number. I look for a simply method in Fluent that it doesn't take much time. Can you help me?

 September 20, 2012, 10:03 #4 Senior Member   Syavash Join Date: Apr 2010 Location: Tehran, Karaj Posts: 185 Rep Power: 7 I see. I think you would be able to do this by means of a UDF. At first you have to calculate local Nusselt number based on surface heat flux and a reference Temperature. Then you should sum all the Nusselt number of all time steps for each computational face separately. At the end you should divide the ُsummation of Nusselt numbers obtained in previous step by the flow time. It can be done by utilizing a Define_Adjust and Define_Execute_on_demand Macro. Bests.

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