Wind protection by model fences in a simulated atmospheric boundary layer

Abstract A brief review of windbreak aerodynamics is presented and tests of model shelter fences in a simulated atmospheric boundary layer are described. Measurements of mean wind velocity, RMS velocity fluctuations and energy spectra for the streamwise velocity component were made in the lee of model fences of permeability 0%, 20%, 34% and 50%. Results of the tests are compared where possible with existing field and wind-tunnel data, with due regard for the uncertainty of hot-wire anemometer measurements in a bluff body wake. The turbulence measurements define the leeward flow regions which are dominated respectively by the bleed flow and by the displacement flow. For these two regions separate empirical relationships between mean velocity and turbulence intensity are given. In these tests the 20% permeable fence gave the best overall reduction in leeward mean velocity. However, in practice it may often be more cost-effective to build a relatively higher fence of greater permeability.