On the choice of a windbreak porosity profile

Measurements of mean windspeed and turbulence were carried out behind two sections of 50% porous fence differing only in the vertical distribution of their porosity. One section of the fence was uniformly porous, the other relatively dense near the ground and open aloft. Slightly greater mean speed reduction was observed near the ground in the near lee of the section which was dense at ground-level without any detrimental increase in turbulence. However, this advantage was offset by less effective protection in the far lee. These findings are consistent with earlier work by Gandemer (1979) and with the predictions of a numerical model of windbreak flow.