Wind load and wind-induced response of hybrid wind turbine towers

The hybrid wind turbine tower with an upper cylindrical section and a lower lattice structure is a promising novel wind resistant structure. However, the wind resistance performance of this type of structure is not yet fully understood, and there is limited correlational research. In this study, high-frequency force balance wind tunnel tests were conducted to measure the wind loads on rigid models of two hybrid tower configurations with different height ratios (the ratio of the height of the lattice part to that of the cylindrical part), under various wind directions, and the wind load characteristics of the towers were analyzed. The linear mode assumption and modal analysis method were then used to calculate the wind-induced responses of both towers at the design wind speed, and the effects of wind direction and tower configuration on the wind responses were evaluated. The results show that, the mean drag coefficients of both towers show consistent patterns with changes in the wind direction, reaching a relatively high value around 1.4 at wind angles of 30° or 45°. Compared to the tower with a smaller height ratio, the one with a larger height ratio exhibits smaller root-mean-square values for both drag and lift coefficients, as well as smaller response, whose resultant displacement and acceleration are approximately 66%～87% of those of the former. The mean drag forces of both hybrid towers are lower than that of the corresponding cylindrical tower. The wind-induced dynamic response of both towers reaches the maximum value at a wind angle of 45°. This paper provides valuable insights for selecting structural configurations in practical engineering applications.