| The mean structure of the separation bubble (SB) along the short roof-axis over the Texas Tech Building is established by wind flow measurement with a three-component sonic anemometer. The pressure distribution on the underlying roof is directly related to the structure of the SB. A concept of 'non-conventional' pressure coefficient is introduced to isolate the effects of wind speed from that of the wind direction on the pressure generation. Times series analyses indicate that fast-and-large fluctuations of the natural wind direction about the normal to the windward wall govern the mechanism of peak pressure generation. Primary peaks of conventional pressure coefficients are often outcomes of combined wind direction fluctuations and wind gusts.; For the conical vortices phenomenon, it is observed, based on flow and pressure measurements, that both the wind direction and the wind speed are important factors governing the pressure generation mechanism. Concerning the patterns of vortices over the leading roof corner, a pair of relatively small vortices form at wind angles about the corner diagonal. At wind angles deviating from the diagonal direction, one larger vortex forms from the flow separation at the edge exposed more to the incident wind, usually accompanied by a smaller one forming at the other edge. The wind angle of 70{dollar}spcirc{dollar} seems to be the upper bound of this phenomenon. Strong vortex circulation and the associated high suctions occur with incident wind gusts at angles conducive to vortex formation. This is different from the situation of the SB, where the direction fluctuation not the direction itself was important. Instantaneous pressures under the roof corner can be satisfactorily predicted from the information of the mean pressure coefficients and the incident wind. Findings made here strongly suggest that inadequacies of simulated winds, in terms of large-and-fast direction fluctuations and gust structures, are responsible for the peak pressure mismatch. |
