Wind and Structures

Techno-Press (테크노프레스)
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Numerical investigation of effects of rotating downdraft on tornado-like-vortex characteristics

  • Cao, Shuyang (State Key Lab of Disaster Reduction in Civil Engineering, Tongji University) ;
  • Wang, Mengen (College of Civil Engineering, Tongji University) ;
  • Zhu, Jinwei (Shanghai Urban Construction Design & Research Institute Shanghai) ;
  • Cao, Jinxin (State Key Lab of Disaster Reduction in Civil Engineering, Tongji University) ;
  • Tamura, Tetsuro (Tokyo Institute of Technology) ;
  • Yang, Qingshan (Chongqing University)
  • Received : 2017.10.18
  • Accepted : 2017.12.29
  • Published : 2018.03.25
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Abstract

Appropriate modeling of a tornado-like vortex is a prerequisite when studying the near-ground wind characteristics of a tornado and tornado-induced wind loads on structures. Both Ward- and ISU-type tornado simulators employ guide vanes to induce angular momentum to converge flow in order to generate tornado-like vortices. But in the Ward-type simulator, the guide vanes are mounted near the ground while in the ISU-type they are located at a high position to allow vertical circulation of flow that creates a rotating downdraft to generate a tornado-like vortex. In this study, numerical simulations were performed to reproduce tornado-like vortices using both Ward-type and ISU-type tornado simulators, from which the effects of rotating downdraft on the vortex characteristics were clarified. Particular attention was devoted to the wander of tornado-like vortices, and their dependences on swirl ratio and fetch length were investigated. The present study showed that the dynamic vortex structure depends significantly on the vortex-generating mechanism, although the time-averaged structure remains similar. This feature should be taken into consideration when tornado-like-vortex simulators are utilized to investigate tornado-induced wind forces on structures.

Keywords

Acknowledgement

Supported by : National Natural Science Foundation of China (NSFC), Tongji University, Central Universities

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