Experimental investigation of the downburst impact angle effect on a cubic structure Part B: Moving microburst observations

Downburst storms cause severe destruction by creating intense and unstable downdrafts. On the other hand, due to the difference in their structure from atmospheric boundary layer storms, it is essential to study and understand these flows under different conditions. Therefore, this study the effects of the impact angle of the downburst and the structure installation angle relative to the surface flow on a cube-shaped model investigates dynamically. The model is placed in front of the downburst in four angles of the storm colliding with the surface(θ), in two directions of the surface flow relative to the structure(α), and in the radial range of X/D=±1.5. Also, the ratio of horizontal displacement speed of this storm(VR) is considered to be 0.06 and 0.12. The results show that the increase of θ and VR caused the location of the maximum pressure coefficient to shift from the central point of the flow meeting the surface to the downstream. Also, increasing α has reduced the range of pressure and force changes by about 25% on the model. In addition, it was found that dynamic downburst caused stronger impacts on the structure and generally, these strong impacts occurred immediately after the downburst passed over the structure.