Periodic pressure gradient.

A7A · December 15, 2012, 01:24

Hi,

I am modelling a 3d periodic flow of air in a tube with wire coil insert (using relizable k-e model), and after 1500 iterations i get a good results of Nusselt number compared to the experimental results, but the friction factor(which is computed this way: f=(dp)/(0.5*density*velocity^2*(length/tube diameter))
is so high compared to the experimental results.

Could you give me any advice about this problem.

Thank you in advance

A7A · December 15, 2012, 08:32

Any ideas?

A7A · December 25, 2012, 03:13

Could you give me any solutions, untill now i couldnt manage to solve this problem.

Thank you in advance.

Kamu · January 15, 2013, 08:38

Quote:

Originally Posted by A7A

Could you give me any solutions, untill now i couldnt manage to solve this problem.

Thank you in advance.

Which value of dp do you use for calculation of f? the correct value should be the pressure gradient under the periodic boundaries panel, you have to multiply it by the length of your tube.

A7A · January 15, 2013, 10:27

Thank you Kamu for your reply

, but there is no need to multiply dp by tube length because its divided by length in f correlation.

A.H.S · November 24, 2021, 01:18

Quote:

Originally Posted by Kamu

Which value of dp do you use for calculation of f? the correct value should be the pressure gradient under the periodic boundaries panel, you have to multiply it by the length of your tube.

Hi, this way had totally help me with this kind of problem but what about CFX. how can I estimate pressure gradian between two periodic zones. I first guess is to use CFD-Post but with what variable?

December 15, 2012, 01:24	Periodic pressure gradient.	#1
A7A Member AHMAD Join Date: Apr 2012 Posts: 54 Rep Power: 0	Hi, I am modelling a 3d periodic flow of air in a tube with wire coil insert (using relizable k-e model), and after 1500 iterations i get a good results of Nusselt number compared to the experimental results, but the friction factor(which is computed this way: f=(dp)/(0.5densityvelocity^2(length/tube diameter)) is so high compared to the experimental results. Could you give me any advice about this problem. Thank you in advance Last edited by A7A; December 25, 2012 at 03:10.*

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December 15, 2012, 08:32		#2
A7A Member AHMAD Join Date: Apr 2012 Posts: 54 Rep Power: 0	Any ideas?

December 25, 2012, 03:13		#3
A7A Member AHMAD Join Date: Apr 2012 Posts: 54 Rep Power: 0	Could you give me any solutions, untill now i couldnt manage to solve this problem. Thank you in advance.

January 15, 2013, 10:27		#5
A7A Member AHMAD Join Date: Apr 2012 Posts: 54 Rep Power: 0	Thank you Kamu for your reply , but there is no need to multiply dp by tube length because its divided by length in f correlation.