Abstract
The author deals with the effect of wind shelter both theoretically and experimentally, making use of aerodynamical results according to the modern similarity theory of turbulence.
The geometrical and dynamical characteristics of the effective zone of shelter-hedge where the wind velocity is diminished are discussed theoretically by means of knowledges concerning the structure of wind near the ground, i. e., the logarithmic velocity distribution U(z), the vertical distribution of life-time of the largest vertical turbulon τ0(z) and the roughness parameter Z0 of the ground surface. Thus the characteristic length L of effective zone of the shelter-hedge of the height h is obtained approximately in terms of parameters mentioned above as
L-U (h) τ0 (h)
-h log (h/Z0)
and is further deduced to be in proportion to h8/7 provided the logarithmic law of velocity distribution might be substituted by the 1/7 power law such as U(z)-Uc (Z/c)1/7 where c and Uc means a certain characteristic height and the wind velocity at that height.
These theoretical results, indicating the influences of both hedge height and roughness parameter on the length of effective zone, are examined experimentally in the wind tunnel with good results, where the turbulent boundary layer is artificially set up with roughness of several types.
