Increasing of total temperature

Roland R · December 16, 2011, 13:53

Hello,

I have a general 3D flow field. It contains a large region (a tube) where strong swirling zone occurs. In this zones the total temperature always becomes larger than the inlet total temperature which was defined as boundary condition. The walls are adiabatic and free slip. I don’t understand this. How can the total temperature increase above the inlet total temperature if there is not heat input and friction at the walls. Is this because of the viscosity (internal friction) of material?

Regards
Roland

ghorrocks · December 16, 2011, 16:08

Have you got viscous dissipation turned on? Yes, this could be one explanation.

Also if the simulation is not fully converged you could get this. Also inadequate mesh resolution could contribute.

stumpy · December 20, 2011, 12:04

Is the total temperature locally above the inlet value or is it the massFlowAve(Total Temperature) on a slice plane through the tube? If it's just locally then that's allowed to happen physically. It's similar to a local rise in Total Pressure (see "Rise of Total Pressure in Frictional Flow" - http://adsabs.harvard.edu/abs/1995AIAAJ..33..772I)

balkrishan · March 29, 2018, 02:15

Quote:

Originally Posted by ghorrocks

Have you got viscous dissipation turned on? Yes, this could be one explanation.

Also if the simulation is not fully converged you could get this. Also inadequate mesh resolution could contribute.

What do you mean by inadequate mesh? and how it causes the temperature increase more than total

Gert-Jan · March 29, 2018, 04:08

Overshoots have been there since man invented numerical methods. These overshoots can be persistent when your mesh has low quality.

December 16, 2011, 13:53	Increasing of total temperature	#1
Roland R Senior Member Roland Rakos Join Date: Mar 2009 Posts: 131 Rep Power: 17	Hello, I have a general 3D flow field. It contains a large region (a tube) where strong swirling zone occurs. In this zones the total temperature always becomes larger than the inlet total temperature which was defined as boundary condition. The walls are adiabatic and free slip. I don’t understand this. How can the total temperature increase above the inlet total temperature if there is not heat input and friction at the walls. Is this because of the viscosity (internal friction) of material? Regards Roland

December 20, 2011, 12:04		#3
stumpy Senior Member Join Date: Apr 2009 Posts: 531 Rep Power: 21	Is the total temperature locally above the inlet value or is it the massFlowAve(Total Temperature) on a slice plane through the tube? If it's just locally then that's allowed to happen physically. It's similar to a local rise in Total Pressure (see "Rise of Total Pressure in Frictional Flow" - http://adsabs.harvard.edu/abs/1995AIAAJ..33..772I) TommyM likes this.

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December 16, 2011, 16:08		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Have you got viscous dissipation turned on? Yes, this could be one explanation. Also if the simulation is not fully converged you could get this. Also inadequate mesh resolution could contribute.

March 29, 2018, 04:08		#5
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	Overshoots have been there since man invented numerical methods. These overshoots can be persistent when your mesh has low quality.