Aerodynamic calculation of loads and dynamic behavior of wind ...

of the distribution are far from this model, rendering such an approximation
inappropriate.
The factors that seriously affect the turbulence intensity are the roughness of the
ground surface, the topographical features and the thermal behavior of the
atmosphere. Concerning the ground surface, the influence of its characteristics is
limited to a certain height, above which the air flow can be considered unobstructed
and is only affected by the large scale pressure differences and the earth’s rotation.
This state of the air flow is named “geostrophic wind”. Apparently, however, this is
not the case for the type of wind loading the various structures, due to their proximity
to the ground. A wind turbine, for example, is exposed to a significantly disturbed air
flow, at the atmosphere’s lowest layer, the so-called “boundary layer” (see Fig. 2.2)
Figure 2.2: Boundary Layer: A common occurrence with fluid flow over a solid surface
Since several equations are proposed for the determination of turbulence
intensity’s values by different standards, a summary chart (Fig. 2.3) would be useful:
15