Experimental study of surface jet-type winds on a generic escarpment geometry and their application to downburst-like flows

Yongli Zhong , Qiyan Wu , Xiangjun Tan , Zhitao Yan , Wenshan Shan , Zulin Huang

Abstract

Downburst outflows interacting with uplifted terrain features, such as escarpments, can substantially accelerate local near-ground wind speeds and thereby aggravate wind hazards. However, existing downburst research has predominantly focused on wind-field characteristics over flat and smooth terrains, whereas the effects of elevated terrains remain insufficiently understood. To address this gap, the present study conducts an experimental investigation into how escarpment terrain modifies the mean and fluctuating components of downburst-like wind velocity profiles. A downburst-like flow was reproduced using a plane wall-jet facility, and the influences of escarpment slope angle and the upstream (pre-escarpment) surface roughness were systematically examined. The results show that the escarpment terrain significantly impacts the mean and fluctuating wind profiles of the downburst at the escarpment top-position, and the wind profile no longer maintains the "nose" shape, compared to that from the flat ground. Moreover, the escarpment has an apparent obstructive effect on the mean speed profile of the downburst-like wind, showing a deceleration effect at the escarpment toe-position, exhibiting wind speed characteristics similar to those of the flat ground in the mid-escarpment area, and presenting a significant speed-up effect at the escarpment top-position. Meanwhile, the influence of the escarpment on the speed-up ratio at the escarpment top is mainly concentrated in the near-wall region, with the maximum value reaching 1.5. The influence of the roughness area is mainly occurring on the outer layer of the downburst-like flow, and the roughness area significantly impacts the wind speed-up ratio along the entire wind profile.

Key Words

downburst-like flow; escarpment terrain; mean wind speed; speed-up ratio; turbulence intensity; wind tunnel test

Address

Yongli Zhong — 1)School of Civil and Hydraulic Engineering, Chongqing University of Science and Technology, Chongqing 401331, China 2)Chongqing Key Laboratory of Disaster Prevention and Reduction in Power Transmission Engineering, Chongqing University of Science and Technology, Chongqing 401331, China 3)Wind Engineering and Aerodynamics Research Center, Chongqing University of Science and Technology, Chongqing, 401331, China
Qiyan Wu — School of Civil and Hydraulic Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Xiangjun Tan — School of Civil and Hydraulic Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Zhitao Yan — 1)School of Civil and Hydraulic Engineering, Chongqing University of Science and Technology, Chongqing 401331, China 2)Chongqing Key Laboratory of Disaster Prevention and Reduction in Power Transmission Engineering, Chongqing University of Science and Technology, Chongqing 401331, China 3)Wind Engineering and Aerodynamics Research Center, Chongqing University of Science and Technology, Chongqing, 401331, China 4)School of Civil Engineering, Chongqing University, Chongqing 400045, China
Wenshan Shan — School of Civil and Hydraulic Engineering, Chongqing University of Science and Technology, Chongqing 401331, China
Zulin Huang — 1)School of Civil and Hydraulic Engineering, Chongqing University of Science and Technology, Chongqing 401331, China 2)Chongqing Key Laboratory of Disaster Prevention and Reduction in Power Transmission Engineering, Chongqing University of Science and Technology, Chongqing 401331, China

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