Articles
CONTRIBUTION TO THE STUDY OF WINDBREAKS IN THE WIND TUNNEL
Although numerous investigations have been carried out, the influence of windbreaks and shelterbelts on the concerned micrometeorological phenomena has not been globally studied.
These phenomena are highly affected by the aerodynamic characteristics of shelterbelts.
In order to understand the natural phenomenon with all its varieties a model study of wind flow in the neighbourhood of windbreaks and shelterbelts was carried out in a wind tunnel using model trees made of plastic material.
The model trees represent poplars (Populus canadensis) 10 and 18 m high, cypresses (Cupressus sempervirens) 5, 10 and 18 m high and schrubs 2 m high.
The reduction scale of the model trees in the wind tunnel was about 1:100. Typical patterns of windbreaks have been studied here usually met in Nature.
The parameters for the windbreak studied in this investigation were height and porosity, while for the wind flow were wind velocity profile, turbulence intensity and ground surface roughness.
An air – water – analogy model was used to visualize the aerodynamic phenomenon in the experimental water flume.
The mean and fluctuating velocities were measured in the whole region upstream, over and downstream the model windbreak.
Using several permeable and solid fences as well as rough surfaces consisting of sand layers, it was possible to establish the desired mean velocity profile as well as the desired turbulence intensity of the flow in order to produce a turbulent flow field similar to field conditions.
Preliminary results of this study show that the protective effect of windbreaks consisting of poplars, cypresses and shrubs highly depends on the geometric characteristics of the screen as well as the velocity profile and turbulence characteristics of the blowing wind.