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wondering about conjugate heat transfer with forced convection

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Message 1 of 5
pei-ying.hsieh
541 Views, 4 Replies

wondering about conjugate heat transfer with forced convection

Dear Autodesk CFD experts,

 

I am wondering about modeling conjugate heat transfer with forced convection.  In the tutorial, it solved the flow field without thermal, and then, freezed the flow flow and only solve for thermal (I am running a transient case).  Because I have a couple of heaters inside the domain, and hot air flows upwards, does heat affects flow field, ie, flow field will change after temperature goes up?  Is there a need (or a way) to recompute the flow field based on new temperature field after some time steps?

 

Thanks!

 

Pei-Ying

4 REPLIES 4
Message 2 of 5
Jon.Wilde
in reply to: pei-ying.hsieh

Simply do not use Auto Forced Convection, as this is what tells CFD to run flow then thermal. You need to run both together.

 

I would have thought you will also need air_variable (so the density can change with temperature) and gravity on too.

Message 3 of 5
pei-ying.hsieh
in reply to: Jon.Wilde

Hi, Jon,

 

I did not have Auto Forced Conection turned on.  I remembered someone told me that this approach was no longer recommended after 2014.

 

I did set air to variable and gravity turned on. 

 

In general, it is more expensive to solve for flow field and flow field does not change rapidly due to thermal changes.  So, I do believe that, there is an advantage to solve for flow only, then, solve for energy.  However, energy equation does affect flow after some period of time, so, is it necessary to re-solve for flow again after some period of time?  If yes, how? It will be straight forward for steady state, but, I am interested in transient.

 

Thanks!

 

Pei-Ying

Message 4 of 5
Jon.Wilde
in reply to: pei-ying.hsieh

It is fine to use Auto Forced Convection, when you only have forced convection.

 

Sure, you could do that then. Solve for flow and thermal, stop it and then just solve for thermal with the flow off, so it will be locked to the last result.

If you are concerned about the flow changing, it is best to just forget the assumptions and run flow + thermal throughout.

Message 5 of 5
pei-ying.hsieh
in reply to: Jon.Wilde

Thanks Jon!

 

Pei-Ying

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