The aerodynamics of wind breaks is studied in a simulated boundary layer. Flow patterns and shelter effects in the lee of different fences are described and discussed in terms of efficiency relating to pedestrian comfort. Based on the generally accepted critical level of discomfort, and the corresponding discomfort wind frequencies, we suggest a shelter parameter. The results downstream are given in horizontal planes by nets of isocurves (isotachs, isoturbs, isoshelters) with specific levels in relation with discomfort wind frequencies. The influence of the permeability, the shape, the sizes, the wake ventilation are discussed and new designs are suggested: for instance, the association of two wind breaks seems to be very good; the high horizontal speed gradient at the corner can be easily reduced as can the overspeed, etc. In fact, depending both upon the comfort level people want and upon the area (downstream) the best" protection will not be given by the same wind break aerodynamics. The influence of the vegetation on the wind shelter (full scale experimentation) is also described. The discussion is in terms of the analysis of energy spectra. © 1979."
