# Wind Actions - Vortex Shedding

• guaiamum

#### guaiamum

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

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