# Calculating Turbulance Parameters of External Flow

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 June 7, 2017, 19:21 Calculating Turbulance Parameters of External Flow #1 New Member   Join Date: Feb 2017 Posts: 6 Rep Power: 8 Hello all. In my case, there is a chimney that disperses pollutants to open atmosphere( enclosure). It is velocity boundary condition. How can I calculate some paramters such as turbulence characteristic length or hydraulic diameter? Regards,

 June 8, 2017, 03:23 #2 Member   Baris PULAT Join Date: Sep 2016 Location: Italy Posts: 59 Rep Power: 8 Hello teuton, I highly recommend you to do a quick research before asking a question for the next one. For your question https://www.cfd-online.com/Wiki/Hydraulic_diameter check out this link. I think you will understand what to do with hydraulic diameter and turbulence length scale. To calculate hydraulic diameter you should use the dimension of your enclosure and then using hydraulic diameter to calculate your turbulence length scale. Don't forget that this turbulence length scale is an estimation for fully developed inlet boundry condition. I also want to note that depending on your boundry conditions a vortex shedding can happen behind your chimney. So if needed adding helical strakes to the chimney can be handy for your design. Best Regards, Baris KaLium likes this.

 June 18, 2017, 11:56 #3 New Member   Join Date: Feb 2017 Posts: 6 Rep Power: 8 Hello Baris, Thank you for reminding me very basics of fluid mechanics, but my concern is about modelling atmospheric boundary layer. Anyway, I found what I was looking for. I suggest everyone who wants to model atmospheric bc. to read Bert Blocken and P.J. RICHARDS's articles. Regards,

June 19, 2017, 04:30
#4
Member

Baris PULAT
Join Date: Sep 2016
Location: Italy
Posts: 59
Rep Power: 8
Hello teuton,
Quote:
 In my case, there is a chimney that disperses pollutants to open atmosphere( enclosure). It is velocity boundary condition. How can I calculate some paramters such as turbulence characteristic length or hydraulic diameter?
With limited information about what you really need. And regarding to your question i think the answer is proper.

Regards,

Baris

 Tags atmospheric bl, flow around buildings, urban airflow