Vortex Shedding in Eurocode 2

[StoyanAndreev]

I am performing strength and deflections checks of an existing 150 m tall RC concrete chimney with varying cross section according to Eurocodes.
In EN1991-1-4 (Wind Loading) we can find this text:
E.1.2 Criteria for vortex shedding
(1) The effect of vortex shedding should be investigated when the ratio of the largest to the smallest crosswind dimension of the structure, both taken in the plane perpendicular to the wind, exceeds 6.
(2) The effect of vortex shedding need not be investigated when
Vcrit,i>1,25.vm
My question is how do I calculate the dimension ratio in (1) for outer diameter at the top of the chimney is 3.60 m, the diameter at the bottom is 13.2 m.
Thank you!

 

[PSEPK]

From the given statement, IMHO, it should numerically be equal to the ratio of the largest diameter to the smallest diameter (i.e., the ratio of bottom diameter to the top diameter).

 

[pikku14]

The ratio to be used is the length/height to the diameter so 150/13.2 or 150/3.6 both of which > 6, therefore vortex shedding should be investigated

 

[StoyanAndreev]

Thank you pikku14, I was thinking the same thing, but I needed confirmation, because it is a bit unclear written IMO.

 

[SAIL3]

If the statement by the OP means that the greater the taper on a stack, the greater the risk of vortex-shedding problems...this does not make any sense to me at all....