# Backflow turbulent intensity?

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 January 10, 2016, 23:50 Backflow turbulent intensity? #1 New Member   Jongmin Choi Join Date: Jan 2016 Posts: 14 Rep Power: 9 Hi, I'm beginner of ansys fluent. As doing tutorials I have a question about backflow turbulent intensity. I haven't learned any knowledge about that so I couldn't understand it. Could you explain about backflow turbulent intensity? How could I decide that value for ansys fluent??? Vinay94 likes this.

 January 11, 2016, 14:41 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,146 Rep Power: 61 When there is backflow, your outlet is an inlet. Thus you need to specify back-flow conditions in the event that there is any back-flow. Just as you might specify pressure, temperature, turbulence, etc at inlets, you need to do the same for outlets. Just take your best guess as to what a suitable value is. If you knew what the backflow turbulence was, then you would already know the flow field and wouldn't be doing CFD in the first place. ama294, Jongmin Choi and Vinay94 like this. Last edited by LuckyTran; January 27, 2016 at 02:41.

 January 27, 2016, 02:17 #3 New Member   Jongmin Choi Join Date: Jan 2016 Posts: 14 Rep Power: 9 Thank you for your sincere ansewering

September 7, 2016, 14:49
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Abdulaziz Abutunis
Join Date: Aug 2014
Posts: 41
Rep Power: 10
Quote:
 Originally Posted by LuckyTran When there is backflow, your outlet is an inlet. Thus you need to specify back-flow conditions in the event that there is any back-flow. Just as you might specify pressure, temperature, turbulence, etc at inlets, you need to do the same for outlets. Just take your best guess as to what a suitable value is. If you knew what the backflow turbulence was, then you would already know the flow field and wouldn't be doing CFD in the first place.
Hi LuckyTran,

First of all, thanks for your answer and could you please specify if the turbulence intensity affected by the application. for example if it is a rotor then the turbulence intensity will be higher than if it is a static object facing the flow. And in case of airfoil, should the turbulence intensity at the inlet be little larger than at the outlet.

Thanks
Aziz

 September 7, 2016, 15:00 #5 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,146 Rep Power: 61 The backflow turbulence intensity is affected by everything. Yes, it depends on each individual application. The turbulence intensity is a local variable. It may locally decrease or increase depending on the local details of the flow. The turbulence intensity in the freestream can decrease because of decaying turbulence whereas the turbulence intensity can be enhance by the wake of a rotor/stator. ama294 likes this.

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