Using data sampling as initial condition

tinhtt · September 19, 2014, 08:07

Hi Fluent experts,
In transient simulation of Fluent, activating data sampling can obtain the temporal average data. I would like to use these data sampling results as initial condition for a STEADY simulation (same parameters as previous ones, except STEADY).
Could you please give me the advice how to overcome this problem? Thank you!

tinhtt · September 19, 2014, 08:09

Ps: Actually, I need to use data sampling results from transient simulation as the frozen fields for the next steady simulation.

LuckyTran · September 19, 2014, 08:35

Some context would help. Can you not just switch settings from a transient simulation to a steady one? If you do this switch without re-initializing the current fields from the transient simulation will be used as the initial values for your steady simulation.

I know of one way to export, may not be the best way. It works only if your next steady simulation is done on the same domain or same mesh.

Write an interpolate file. File=>interpolate=>write data
Write the variables you want over each zone

Then read this file into your steady simulation.

It might work better if you switch your transient simulation to a steady one before writing the interpolate file.

Ok, now I see you want to use the data sampling results. Hmms.

LuckyTran · September 19, 2014, 08:54

Ok try this. First create a custom field function for each of your statistics. On the GUI that's under define=>custom field functions.
Choose unsteady statistics => velocity, etc. and select. Your custom field definition is now the current field for the mean velocity, etc. Give an appropriate name for your custom field.

Now you can patch your existing fields to your custom field. That is, patch X velocity using the custom field for the mean X velocity. To do this go to initialize=>patch. Select x-velocity. Check the box for use field function, select your field function created earlier. Select appropriate zones and patch.

Now you have replaced the instantaneous velocity field with the time-averaged one. It can now be manipulated using normal methods. You can now switch to steady and proceed.

tinhtt · September 19, 2014, 09:16

Thank you so much LuckyTran!
Initialization by patching the custom field functions works perfectly as my expectation.
Thanks again and best wishes to you!

Thanh Tinh Tran

September 19, 2014, 08:07	Using data sampling as initial condition	#1
tinhtt New Member Join Date: Sep 2009 Posts: 19 Rep Power: 17	Hi Fluent experts, In transient simulation of Fluent, activating data sampling can obtain the temporal average data. I would like to use these data sampling results as initial condition for a STEADY simulation (same parameters as previous ones, except STEADY). Could you please give me the advice how to overcome this problem? Thank you!

September 19, 2014, 08:35		#3
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,751 Rep Power: 66	Some context would help. Can you not just switch settings from a transient simulation to a steady one? If you do this switch without re-initializing the current fields from the transient simulation will be used as the initial values for your steady simulation. I know of one way to export, may not be the best way. It works only if your next steady simulation is done on the same domain or same mesh. Write an interpolate file. File=>interpolate=>write data Write the variables you want over each zone Then read this file into your steady simulation. It might work better if you switch your transient simulation to a steady one before writing the interpolate file. Ok, now I see you want to use the data sampling results. Hmms. tinhtt likes this.

September 19, 2014, 08:54		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,751 Rep Power: 66	Ok try this. First create a custom field function for each of your statistics. On the GUI that's under define=>custom field functions. Choose unsteady statistics => velocity, etc. and select. Your custom field definition is now the current field for the mean velocity, etc. Give an appropriate name for your custom field. Now you can patch your existing fields to your custom field. That is, patch X velocity using the custom field for the mean X velocity. To do this go to initialize=>patch. Select x-velocity. Check the box for use field function, select your field function created earlier. Select appropriate zones and patch. Now you have replaced the instantaneous velocity field with the time-averaged one. It can now be manipulated using normal methods. You can now switch to steady and proceed. tinhtt likes this.

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September 19, 2014, 08:09		#2
tinhtt New Member Join Date: Sep 2009 Posts: 19 Rep Power: 17	Ps: Actually, I need to use data sampling results from transient simulation as the frozen fields for the next steady simulation.

September 19, 2014, 09:16		#5
tinhtt New Member Join Date: Sep 2009 Posts: 19 Rep Power: 17	Thank you so much LuckyTran! Initialization by patching the custom field functions works perfectly as my expectation. Thanks again and best wishes to you! Thanh Tinh Tran