Measurements of the static pressure near the surface in the atmospheric boundary layer

Abstract

Measurements have been made of the three components of velocity and of the static pressure in the lowest 10 ​m of the atmospheric boundary layer. The measurements reported here were made on two occasions: the first with a single 10 ​m mast and the second with four 6 ​m masts. One-hour duration measurements at a sampling rate of 10 samples s−1 were processed for statistical properties including an assessment of the mean static pressure, and the time series processed for spectral properties. The mean velocity profile followed the expected boundary-layer log-region. An estimate of the mean static pressure compared to that above the boundary layer has been made and shows a dependency on the RMS (Root Mean Square) of dynamic pressure. The spectra of wind velocity and wind dynamic pressure follow the expected n−5/3 power-law decay rate in the inertial subrange, whereas static pressure spectra followed a decay rate close to n−4/3 - a result that was not predicted by published theory. Limited comparisons have been made with measurements from wind-tunnel boundary-layer flows, and with one other full-scale experiment. There is evidence from these comparisons that the static pressure spectra has a decay rate close to n−4/3 but there is also evidence of Reynolds-number sensitive. These measurements were made as part of a study of wind effects on buildings. The distinct spectral pattern of static pressure compared to that of dynamic pressure is a potential aid to identifying their separate contribution to wind loading and natural ventilation.