Abstract
The computational fluid dynamics (CFD) simulation on the butte was carried out to obtain the wind field characteristics for a specific mountain in the hilly area of eastern China. Then, the speed-up ratios of butte at each location distributed by height were calculated. The simulation results were compared with the specified value of mountain wind field acceleration ratio in various codes. The finite element model of the transmission tower line system is established by ANSYS, and the wind-induced vibration response of the structural system under the single mountain wind field is calculated, which is compared with the results of flat ground. The results show that the mountain will hinder the fluid passing through it. There is a deceleration zone in front of the mountain and a flow separation phenomenon behind the mountain. The speed-up ratios at the butte top where accelerating effect are the biggest among all positions of the butte. As the height increases, they approach 1. The speed-up ratios calculated by the Chinese code and the Australian code are linearly changing along the ridge of the butte and are symmetric at the windward side and leeward side. The biggest speed-up ratios are calculated by the Chinese code, and the smallest ratios are calculated by CFD. The wind-induced vibration response of the transmission tower line system is influenced by the wind speed-up ratios and reaches the maximum at the top of the butte. The simulation results at the windward side are close to the values calculated by the Australia code and the Euro code, but at the top and leeward side, they are far smaller than others.
Highlights
Introduction e topography of China is high in the west and low in the east with rolling country and plains in the east, which has obvious characteristics of the mountain wind field
As the carrier of cross-regional power transmission, the transmission tower line system will inevitably be built on the mountain, which is correspondingly related to the influence of complex geological/natural environments [1–3]
For high-rise structures with complex shape and high height, it is necessary to consider the downwind wind load and the vortex caused by the flow effect under the crosswind load or even temperature effect [6–8]. e alternating vortex shedding generates the pulsating loads, and when it is close to the natural frequency of the structure, it will lead to crosswind vortex-induced resonance (VIR), which would do tremendous harm to the transmission tower [9]
Summary
Since a two-dimensional (2D) mountain wind field cannot accurately describe the wind movement process in the whole space, this paper chooses to simulate a three-dimensional (3D) axisymmetric butte for the wind field calculation. e selected mountain model is a 3D cosine typical butte with a diameter of 400 m at the bottom and a height of 100 m. e mountain contour can match the following equation: z(x, y) Hcos2⎡⎢⎢⎣πx2 + y20.5⎤⎥⎥⎦,. Is model is centered on the mountain top; the calculation domain size is 1.6 km upstream and is 2.4 km downstream with a blocking rate of less than 3%. The grid division is determined as follows: the grid resolution of the calculation area, which is centered on the top of the mountain within 600 meters along and perpendicular to the flow direction, is 4 m and is increased at a growth rate of 1.05 times in outward direction, the grid at the inlet and side of the flow field is increased to 30 m, and the grid at the outlet of the flow field is increased to 40 m.
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