Improved toggle-brace viscous damper for vibration mitigation of wind turbine blade

Blades are one of the most critical components of wind turbine systems, often operating under harsh environments and complex conditions [1]. As the core component of a wind turbine, the proper functioning of the blades directly impacts the overall efficiency of the turbine. Blade vibrations not only interfere with the surrounding dynamic flow field, altering their aerodynamic characteristics and thereby affecting the power generation efficiency of the wind turbine [2], but also, for blades that can reach lengths of hundreds of meters as shown in Fig. 1, these vibrations can generate significant dynamic loads. Vibration mitigation of flexible structures under varying environmental conditions is a significant challenge in engineering [3], [4], [5], [6], [7], [8], [9], [10]. This accelerates fatigue damage to the turbine, potentially leading to severe malfunctions. Therefore, conducting in-depth research on blade vibrations and exploring effective vibration mitigation strategies is of paramount academic importance and holds profound significance for practical engineering applications.

Blade vibration behavior is influenced by both aerodynamic and structural damping. While the former method is straightforward and effective, it can adversely affect the turbine’s power output. Furthermore, the design of aerodynamic devices is intricate, heavily reliant on load characteristics, and often necessitates wind tunnel tests and numerical simulations. Conversely, mechanical methods that introduce damping without altering the blade’s aerodynamic profile have become increasingly popular due to their negligible impact on power output. This approach not only offers efficient vibration suppression but is also easy to implement and cost-effective [12], [13], [14]. Over recent decades, various strategies to enhance structural damping have been employed, including passive control [15], [16], active control [17], [18], [19], [20], and the semi-active control [21], [22], [23]. The principal advantage of active and semi-active solutions is their capacity to continuously adjust control forces or damper parameters in response to dynamic excitations and structural changes. For example, Huang et al. [24] utilized semi-active tuned mass dampers (STMD) to mitigate edgewise vibrations in floating wind turbine blades, optimizing the stiffness of each STMD using a semi-active control strategy based on short-time Fourier transform (STFT). Despite promising numerical results, the high costs, design complexities, and power requirements of active and semi-active devices limit their practical application in wind turbine blades. In contrast to active and semi-active solutions, passive damping devices are considered more feasible for practical applications due to their cost-effectiveness and robustness. Various types of passive dampers, such as roller dampers [25], [26], circular liquid column damper [27], tunned mass dampers (TMD) [14], tuned mass-damper-inerter [28], and tuned liquid dampers (TLD) [29], tuned cable-inerter system [8], inerter-based tuned mass system [22], and viscous damper [30] have been proposed to suppress flapwise and edgewise vibrations of blades. Due to the turbulence adhering to the blade, the aerodynamic damping in the flapwise direction is more pronounced, thereby implying the response to be mainly quasi-static [31]. On the contrary, due to the inherently lower aerodynamic damping in this direction [32], [33], edgewise oscillations is dominated by the dynamic response rather than quasi-static [33]. It seems that the vibration control of blades in edgewise vibration by the passive damping device can be more rational [34]. In fact, the passive damping device can also obtain a good performance in the vibration mitigation of blade in flapwise direction since the vibration amplitude is much larger than that in the edgewise direction, as illustrated in Table 1.