جستجوی مقالات مرتبط با کلیدواژه "impact angel" در نشریات گروه "مکانیک"

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.

A Downburst can produce divergent outflow wind on the ground surface, which is different from the behavior of atmospheric boundary layer flows. In this research, the effects of 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 a simulator that was made for this thunderstorm. Simulation of this flow is created by a blower whose task is to uniformize the flow created by the fan embedded behind it. 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 at the X/D locations. In addition, a good agreement has been observed between the data comparison of this study and previous studies. It was observed that at the center of the downburst for all θs, the structure has a positive pressure coefficient along its sides. By moving away from the center of the storm, the flow behavior is similar to the boundary layer flows. By increasing θ, it was found that the difference of pressure coefficient between the windward side relative to the roof and the backward sides, increased, which in the worst case has changed by about 80%. By examining the direction of flow to the model, it was found that the force coefficients when the model is at α=45°, are about 35% less than when the model is at α=0°. Finally, it was found that at X/D=1, the maximum force coefficient is applied to the structure.