| The effects of turbulence and its scales on the pressure distributions around two three-dimensional square prisms, one with dimensions twice the other, are investigated. The experiments were carried out in the St. Anthony Falls Laboratory boundary layer wind tunnel. Mean and fluctuating pressure distributions on the front, side, wake and roof faces of the prismatic models exposed to three boundary layer flows incident at an angle of zero degree are presented. Three boundary layers which are essentially wind tunnel simulations of a neutral urban atmospheric boundary layer at different scales were generated in the wind tunnel for this purpose. The characteristics of the boundary layers generated are presented and discussed in detail including comparisons with atmospheric data. Longitudinal integral length scales for the three boundary layers were considerably different.;The pressure distributions on the side and roof faces of both the models in the three boundary layers showed, in general, reattachment of the flow. The trends of the pressure distributions including the minimum pressure distributions were the same for the three boundary layers for both the models. The mean pressure coefficients normalized with the freestream velocity were nearly the same for two of the boundary layers, where the turbulence intensities were close, while they were generally lower for the other boundary layer, for both the models. The rms pressure coefficients measured for the three boundary layers for each model were close to each other and the scatter band for the minimum pressure coefficients was similar for the three boundary layers. There is no indication of a significant effect of integral length scale on the pressure distributions.;The look-up inversion procedure and the yaw function approach used in the calibration and application of X-wires are discussed and efficient implementations of the procedures are presented. While in general the yaw function approach was found to give significant errors in flow angle values, the procedure yielded reasonably good flow quantities for flows of interest to the present study. |
