The effects of stationarity on the pressure coefficients measured on a low-rise building

The primary objective of this investigation is to establish whether or not nonstationarity has a significant effect on the pressures (and the resulting pressure coefficients) measured on the full-scale building at WERFL. Four flow regimes (stagnation, wake, separated and conical vortex) using three pressure taps located on the wall, the roof edge, and the roof comer were chosen for this investigation. Summary statistics from 15-minute duration runs collected in collection Modes 15, 28, 38, 48, 49, 50, 51, and 52 over a period of 10 years are used in this study. Four categories of stationarity were used for the analysis. Stationary Speed & Stationary Direction (SS), Nonstationary Speed and Stationary Direction (NS), Stationary Speed & Nonstationary Direction (SN), Nonstationary Speed and Nonstationary Direction (NN).

The Kruskal-Wallis test on the Cp mean, rms, min and max pressure coefficients using the 4 stationarity categories were initially performed to establish a statistical significant difference in the Cp's associated with each of the stationarity categories. The Kruskal-Wallis test does not remove the effects of flow characteristics on the measured pressure coefficients. To remove the confounding effects of the flow turbulence parameters, the non parametric Friedman Test was used. Roughness length, zo, longitudinal turbulence Intensity lu, lateral turbulence Intensity L, and mean wind speed are used as blocking factors in the Friedman test. In general, stationarity of speed and direction was not significant when the effects of the flow characteristics are considered.