STOCHASTIC DESCRIPTION OF TURBULENT WIND

Abstract

The description of the wind field given below is only intended to provide the theoretical basis that is necessary for the ensuing calculations of structural response. More comprehensive descriptions have been presented by Simiu & Scanlan [4] and by Dyrbye & Hansen [5], where guidelines with respect to the choice of typical input parameters to the stochastic description of the wind field may be found. Such information has also been given by Solari & Piccardo [6]. The most comprehensive source of wind engineering data is provided by Engineering Science Data Unit [7]. Basic theory of turbulence may be found in many text books, see e.g. Batchelor [8] and Tennekes & Lumley [9]. As shown in Fig. 1.3.a the wind velocity vector at a certain point is described by its components (see Eqs. 1.2 – 1.4) in the Cartesian coordinate system (x, y, z) _f with x _f in the main flow direction and z _f in the vertical direction. It is taken for granted that the wind field met by the structure is stationary and homogeneous within the time and space that is considered. A statistical description of the wind field comprises three levels: the long term variation of the mean wind velocity, the short term single point time domain variation of the turbulence components, and finally, the short term spatial distribution of the turbulence components.