STRUCTURE OF THE ATMOSPHERIC BOUNDARY-LAYER BELOW 25-M AND IMPLICATIONS TO WIND LOADING ON LOW-RISE BUILDINGS

Measurements of instantaneous wind velocity have been made in the flow approaching a low-rise building at a position sufficiently far up-stream to be unaffected by the building's pressure field. Analysis of the measurements show that the mean streamwise velocity profile is well represented by a log-law but that velocity spectra, especially close to the ground, depart from the expected form in the inertial sub-range. The work illustrates, through spectral analysis, the requirement to relate surface pressures on a building to the approaching flow originating from a height corresponding to that of the streamline affecting the tapping point. An empirical form of the velocity spectrum is presented which gives a good representation of the measurements made and which has general application to wind engineering.