Experimental study of the effect of impact angle of microburst on a cubic structure – Part A: Stationary microburst observation

A Downburst can produce divergent outflow wind on the ground surface, which is different from the behavior of the atmospheric boundary layer flows. In this research, the effects of the downburst on a cube-shaped structure in two different directions of flow (α), four different ground surface angels relative to the downburst direction (θ), and different radial distances (X/D) relative to the downdraft center were investigated by the simulator that was made for this thunderstorm. The velocity and turbulence intensity of flow was measured at different X/Ds. also, the distribution of pressure coefficient on the sides of the model was measured in the mentioned locations. It was observed that at the center of the downburst in all θs, the structure has a positive pressure coefficient along its sides. By moving away from the center of storm, the behavior of the flow is similar to the boundary layer flows. By increasing θ, it was found that the difference of the pressure coefficient between the windward side relative to the roof and the backward sides, is increased. By changing the direction of the flow to the model (α), it was found that the force coefficients when the model is at α=45°, is about 35% less than when the model is at α=0°. Finally, it was found that the maximum force coefficient is applied to the structure at X/D=1.