How Can We Calculate the Correlation Length L for Vortex Shedding?

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SUMMARY

The discussion focuses on calculating the correlation length "L" for vortex shedding over a circular cylinder, as defined by Eurocode. The parameter "Kw" (effective correlation factor) is dependent on "L/b", where "b" is the crosswind dimension. The expression for maximum displacement due to vortex shedding is given by Ymáx/b = 1/St² x 1/Sc x K x Kw x Clat. The challenge lies in determining "L," which is influenced by the maximum displacement "Ymáx."

PREREQUISITES
  • Understanding of vortex shedding phenomena
  • Familiarity with Eurocode standards, specifically Eurocode 1 - Action on Structures - Part 1-4
  • Knowledge of fluid dynamics concepts such as Strouhal number (St) and Scruton number (Sc)
  • Ability to interpret engineering equations related to wind actions on structures
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  • Research methods for calculating correlation length "L" in fluid dynamics
  • Study the application of Eurocode 1 in structural engineering
  • Explore empirical and analytical approaches to vortex shedding analysis
  • Learn about the relationship between turbulent velocity fluctuations and correlation length
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Structural engineers, fluid dynamics researchers, and professionals involved in wind load analysis on cylindrical structures will benefit from this discussion.

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Please Help!

In dealing with wind induced forces, caused by vortex shedding action over a circular cylinder, we must calculate the parameter "Kw" (effective correlation factor), which depends on "L/b", "L" beeing the "correlation lenght" (Eurocode).

Is there any method, analytical (or empirical), we could use, in order to calculate the parameter "L"?

I do thank you for any kind of help!

Best regards

Luís Fernando
guaiamum2010@gmail.com
 
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Could you define your variables?
 
Thank you, "RandomGuy88"!

According to Eurocode, the largest displacement "Ymáx/b", due to vortex shedding, can be calculated using expression:

Ymáx/b = 1/St^2 x 1/Sc x K x Kw x Clat

I can determinate all of them, except "Kw", which is a function of the so called "correlation lenght" ("L"), which, in turn, is a function of "Ymáx".

And that´s the problem! How can I calculate "L"?

Sorry, if I was too much problematic, and for my bad english!

Best Regards

Luís Fernando
guaiamum2010@gmail.com
 
I have no idea what any of your variables mean. What is b, what is Ymax, what is St, Sc, K...

Is L length over which turbulent velocity fluctuations are correlated? Or is something completely different?
 
Hi, RandomGuy88!

The meaning of those variables, is:

b - Crosswind dimension
Ymax - Maximum displacement due to vortex shedding
St - Strouhal number
Sc - Scruton number
K - Mode shape factor
L - Lenght over which vortex shedding occurs
Kw - Effective correlation length factor

(See Eurocode 1 - Action on Structures - Part 1-4 - General Actions - Wind Actions)

Best Regards

Luís
 

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