CHARACTERISTICS OF LARGE PRESSURES IN REGIONS OF FLOW SEPARATION

Large fluctuating suction pressures are generated in flow separation r egions close to the leading edges on the roof of low rise buildings. T he flow mechanisms that generate these pressures are the 2D separation bubble for flow perpendicular to the edge discontinuity and the 3D co nical vortex for flow at oblique angles to the edge discontinuity. The se pressure fluctuations depart from the Gaussian distribution with si gnificantly greater probabilities at the negative tail of the probabil ity distribution. The largest suction pressures are generated close to the leading corner for a wind orientation of similar to 30 degrees. C onditionally sampled data indicated that progressively larger suction pressures in the separation regions were progressively spatially bette r correlated. Also, time averaged pressures and peak suction pressures were spatially better correlated under the 3D conical vortex than und er the 2D separation bubble.