Modelling in A.L.W.T. the Dynamic Characteristics of the Wind in Mixed Climates
Abstract
The climate behaviour suffers important changes as result of the impact with a rapid extension of the anthropic space. The abrupt modification of season temperature and severe wind storms are put in evidence now all over the world.
Simulation of the dynamic effects of wind action upon the built environment in laboratory is a process of scaling at reduced dimensions of a complex combination of factors insuring similarity between the natural phenomenon and the one artificially reproduced.
Usually, the design wind dynamic action on structures is identified with the so-called extra-tropical depressions, specific for middle global latitudes; the atmosphere is considered neutrally stratified, the vertical profile is in equilibrium with the terrain roughness in A.B.L. The simulations of wind speeds and pressures in the boundary layer of the air moving at the surface of the earth are based on vertical profile of the mean speeds, turbulence intensity, spectral power and histograms of the recorded values. The analysis of data is based on the model of the wind speed in A.B.L. fairly considered as a random, stationary, Gaussian process.
Lately, the observations put in evidence the fact that it is the strong winds associated with thunder storms along with the so called gust fronts that affect the built environment and that they are not stationary and Gaussian processes. The paper presents the analysis of series of measured speeds in the wind tunnel SECO 2 at different time intervals, different sampling rates in different types of boundary layers, analyzing the possibility of reproducing some of the characteristics of the wind speed in a non-neutrally stratified boundary layer.
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