Aerodynamic Characteristics of Steel Tube Transmission Tower Body Under Different Flow Fields

Literature Overview and Research Context

Published in the Journal of Zhejiang University (Engineering Science) in 2019, this study investigates the aerodynamic characteristics of steel tube transmission tower body sections under both uniform laminar and uniform turbulent flow conditions. Funded by the National Natural Science Foundation of China (Grants 51678525 and 51372515) and State Grid Corporation of China, the research is directly relevant to the structural engineering of steel tube lattice towers used in high-voltage power transmission. The study employed high-frequency force balance wind tunnel tests on model sections fabricated according to the geometric proportions of a typical SZ27102 steel tube transmission tower at one-third of its total height.

Wind Tunnel Testing Methodology and Key Aerodynamic Parameters

The experimental program involved the fabrication of tower body section models with varying solidity ratios and aspect ratios, as well as single-face truss models representing the windward face of the tower. The critical aerodynamic parameters extracted from the wind tunnel tests include:

Aerodynamic Parameter	Definition	Significance
Windward face single truss shape factor	Force coefficient for a single truss face	Determines windward loading magnitude
Leeward face load reduction factor	Reduction coefficient for leeward face	Accounts for flow separation and pressure recovery
Tower body section shape factor	Overall force coefficient for the complete section	Determines total aerodynamic loading

The experimental results reveal that under high turbulence intensity inflow conditions, the single truss shape factor decreases while the leeward face load reduction factor increases. This counterbalancing effect results in relatively similar overall tower body section shape factors between the two flow field conditions, which is a practically important finding for wind load design.

Standard Comparison and Code Implications

The study provides a valuable benchmark comparison between experimental results and the recommendations of Chinese and British standards:

Parameter	Chinese Standard Recommendation	Experimental Result	British Standard	Observation
Single truss shape factor	Generally lower than test values	Higher, especially at low solidity	Not directly comparable	Chinese standard is conservative at high solidity but unconservative at low solidity
Leeward face load reduction factor	Higher than test values	Lower than Chinese standard	Lower than Chinese standard	Chinese standard overestimates leeward loading

The findings indicate that the Chinese standard's recommended values for the single truss shape factor are generally lower than the experimentally determined values, with the discrepancy being more pronounced at lower solidity ratios. This suggests that for lightweight steel tube lattice towers with low solidity, the Chinese standard may underestimate the windward face aerodynamic loading. Conversely, the Chinese standard's leeward face load reduction factor is higher than both the experimental values and the British standard values, implying an overestimation of leeward face loading.

Engineering Practice and Design Implications

For engineers involved in the design and assessment of steel tube transmission towers, these findings have direct practical significance. The recommendation to consider the influence of solidity on the single truss shape factor and to appropriately increase the recommended values is particularly relevant for modern lightweight tower designs that employ larger-diameter steel tubes with thinner wall thicknesses, resulting in lower overall solidity ratios. The adjustment of the leeward face load reduction factor downward would result in more accurate and potentially more economical wind load calculations.

From a structural integrity perspective, the aerodynamic loading on steel tube lattice towers is a primary design consideration, particularly for towers located in high-wind regions or coastal areas. The accuracy of aerodynamic coefficients directly influences the calculated wind-induced bending moments, axial forces, and torsional moments in the tower members. Underestimation of windward face loading could lead to inadequate member sizing, while overestimation of leeward loading results in unnecessarily conservative and costly designs.

Study Insights and Reflections

This research exemplifies the critical importance of experimental validation in aerodynamic engineering. The wind tunnel testing methodology, with its careful attention to turbulence intensity and model geometric scaling, provides reliable data that can be used to calibrate and refine design codes. I note with appreciation that the study explicitly compares results with both Chinese and British standards, facilitating international code harmonization discussions. For practitioners in the power transmission industry, I would emphasize that the aerodynamic behavior of steel tube lattice structures is fundamentally different from that of solid-wall structures, and the complex flow interactions within the lattice framework make empirical and experimental approaches indispensable. The recommendation for standards revision based on these findings represents a constructive contribution to improving the safety and economy of transmission tower design.