Is Jet mixing turbulent ?

nalamyogesh · May 3, 2020, 15:26

Hello All,

I am simulating a nozzle flow in which a gas comes out of a convergent nozzle and mixes with surrounding atmosphere before impinging onto a surface normal to the jet flow direction. Both the gases (nozzle flow gas and atmosphere) are miscible.

1. How do I judge if I should use a turbulence model. If by Reynolds number, what should be the characteristic length for a convergent nozzle ?

2. Can jet mixing be always considered turbulent?

3. Is impinging jet always turbulent ?

Thank You!!

CFD_10 · May 3, 2020, 15:51

The Reynolds number for a round jet is:

$Re = {U_j\, D\over \nu}$

Where the characteristic length is the diameter

.

For more details you can check the section 5.1 of the book of Pope "Turbulent flows".

May 3, 2020, 15:26	Is Jet mixing turbulent ?	#1
nalamyogesh Member Yogesh Nalam Join Date: Sep 2012 Location: München, Germany Posts: 54 Rep Power: 13	Hello All, I am simulating a nozzle flow in which a gas comes out of a convergent nozzle and mixes with surrounding atmosphere before impinging onto a surface normal to the jet flow direction. Both the gases (nozzle flow gas and atmosphere) are miscible. 1. How do I judge if I should use a turbulence model. If by Reynolds number, what should be the characteristic length for a convergent nozzle ? 2. Can jet mixing be always considered turbulent? 3. Is impinging jet always turbulent ? Thank You!!

May 3, 2020, 15:51		#2
CFD_10 Member CFD USER Join Date: May 2019 Posts: 40 Rep Power: 6	The Reynolds number for a round jet is: $Re = {U_j\, D\over \nu}$ Where the characteristic length is the diameter . For more details you can check the section 5.1 of the book of Pope "Turbulent flows". nalamyogesh likes this. Last edited by CFD_10; May 4, 2020 at 03:33.

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