Interrelations between the Structure of Wind near the Ground and Its Observations

Abstract

The purpose of this paper is to make clear the several statistical properties of turbulence in the natural wind near the ground. Making use of the similarity hypotheses of locally isotropic turbulence, the author builds up a structural model of the turbulent flow field of natural wind, in which the dissipation rate of turbulence energy is considered to depend upon both the distance z from the ground surface and the mean wind velocity U. Thus the properties of the smallest turbulon in wind, which is naturally regarded to be locally isotropic, are expressed as functions of z and U. On the other hand, the scale of effective largest turbulon in horizontal directions is considered to depend upon the averaging-time (time duration of observation) T both in the Eulerian and Lagrangian meaning.
Eventually several statistical quantities. _??_. g., gustiness of wind, turbulent diffusion coefficient, etc., characterizing the turbulence in wind, are expressed in terms of z, U and T, and some of these results are compared with the practical observations. and they are found to be in good agreement.