Turbulent intensity at inlet

yashb97 · January 28, 2021, 08:35

Hello,

I am trying to simulate flow inside a 2d nozzle. I was having issues with high turbulent intensity values. However, I found that the turbulent intensity at the inlet is about 15% and is uniform along the inlet (vertically).
How is this value determined? As in the inlet boundary conditions, a turbulent intensity of 5% is set.

atul1018 · January 29, 2021, 08:54

Hello

Assuming 5% turbulent intensity should be enogh to get fully developed turbulent flow at the inlet. However, The turbulent intensity at the inlet can be also estimated using the Raynolds number.

See here: https://www.cfd-online.com/Wiki/Turbulence_intensity

yashb97 · January 29, 2021, 10:08

Hello,

Thank you very much for your response. However, I do not have an issue determining the turbulent intensity at inlet. As boundary conditions, I have set turbulent intensity at the inlet to be 5%. However, after running the simulation, when trying to plot the turbulent intensity values at the inlet, I am getting 15% instead of 5%. I'm not sure why this is

January 28, 2021, 08:35	Turbulent intensity at inlet	#1
yashb97 New Member Join Date: Jan 2021 Posts: 13 Rep Power: 5	Hello, I am trying to simulate flow inside a 2d nozzle. I was having issues with high turbulent intensity values. However, I found that the turbulent intensity at the inlet is about 15% and is uniform along the inlet (vertically). How is this value determined? As in the inlet boundary conditions, a turbulent intensity of 5% is set.

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January 29, 2021, 08:54		#2
atul1018 Senior Member Join Date: Jun 2020 Posts: 100 Rep Power: 5	Hello Assuming 5% turbulent intensity should be enogh to get fully developed turbulent flow at the inlet. However, The turbulent intensity at the inlet can be also estimated using the Raynolds number. See here: https://www.cfd-online.com/Wiki/Turbulence_intensity

January 29, 2021, 10:08		#3
yashb97 New Member Join Date: Jan 2021 Posts: 13 Rep Power: 5	Hello, Thank you very much for your response. However, I do not have an issue determining the turbulent intensity at inlet. As boundary conditions, I have set turbulent intensity at the inlet to be 5%. However, after running the simulation, when trying to plot the turbulent intensity values at the inlet, I am getting 15% instead of 5%. I'm not sure why this is