heat transfer convergence

martinD · July 6, 2010, 07:30

Hi,
I am performing RANS simulation on jet impingement (full 3D model) with SST tur. model. I am wondering why the heat transfer convergence is so bad, while the momentum and turbulence are good.
Thx, Martin

ckleanth · July 6, 2010, 07:31

what are the y plus values ?

martinD · July 6, 2010, 08:00

Quote:

Originally Posted by ckleanth

what are the y plus values ?

y+ < 1, actually I was running similar simulation before, only for a 5 degree cut out. there the RMS convergence was comparable. in this case the momentum and turbulence RMS is <10^-5 after 500 iterations, while the heat tr. RMS ~ 5x10^-4 (1000 it.).

ghorrocks · July 6, 2010, 19:42

Errors in heat transfer are typically 20-40% in turbulence modelling, especially when looking at local heat transfer rates (rather than global heat transfer). It is much harder to get heat transfer right compared to momentum. This is explained in any turbulence modelling textbook.

martinD · July 7, 2010, 03:30

thanks for reply.
Martin

July 6, 2010, 07:30	heat transfer convergence	#1
martinD New Member Join Date: Jul 2010 Posts: 14 Rep Power: 16	Hi, I am performing RANS simulation on jet impingement (full 3D model) with SST tur. model. I am wondering why the heat transfer convergence is so bad, while the momentum and turbulence are good. Thx, Martin

July 6, 2010, 07:31		#2
ckleanth Senior Member George Join Date: Mar 2009 Location: Birmingham, UK Posts: 257 Rep Power: 18	what are the y plus values ? __________________ Top 4 tips 1. Knowledge is everything and Ignorance is dangerous. 2. Understand your limitations and try to eliminate them. 3. Get yerself a bike and hoon the chuffer. You will soon learn why dogs like to hang their heads out the car window. 4. Please before asking any questions on how to run simulations in CFX, go though all the tutorials

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July 6, 2010, 19:42		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Errors in heat transfer are typically 20-40% in turbulence modelling, especially when looking at local heat transfer rates (rather than global heat transfer). It is much harder to get heat transfer right compared to momentum. This is explained in any turbulence modelling textbook.

July 7, 2010, 03:30		#5
martinD New Member Join Date: Jul 2010 Posts: 14 Rep Power: 16	thanks for reply. Martin