Numerical verification of a new load alleviation technique for wind turbines in atmospheric turbulence

研究重点的共同目的是改进湍流大气入流中风力涡轮机的计算方法，调查发生的复杂相互作用和载荷循环，对新型载荷减缓概念及其对涡轮机空气动力学的影响进行实验和数值研究，载荷和尾流。建议延长阶段的第一个主要目标是（36个月）目前，该项目是对带有运动学耦合的前缘和后缘襟翼的风力涡轮机的CFD模拟的数值设置和过程链的扩展在湍流流入条件下。这将通过实施流体-结构耦合来确定瞬时襟翼偏转，考虑所有作用力，而不是像现在这样规定它们。计算流体力学代码（FLOWer）将确定襟翼上的非定常气动力和力矩，并将其传递给CSD代码（SIMPACK）。在那里，惯性和重力将被计算，襟翼偏转将被确定。对于非定常CFD模拟中考虑的每个物理时间步长，将以时间精确的方式完成。为了评估正在研究的载荷控制概念和研究出现的空气动力效应，系统的复杂性将依次增加（从稳定入流时带有前缘和后缘襟翼的二维翼型开始，直到湍流大气入流条件下的全尺寸风力涡轮机）。在所有模拟中，将直接计算非定常襟翼偏转。扩展的过程链进行了验证，从两个风洞活动的轮廓与负载控制的概念和风洞数据的模型转子与负载控制的实验数据进行比较。验证后的程序被用来模拟一般的NREL 5 MW风力涡轮机。第二个主要目标是调查襟翼的影响，涡轮机在非额定条件下。这些运行条件导致确定性负载波动和非定常空气动力学效应，这在前两个项目阶段中未进行研究，但对风力涡轮机的寿命有重大影响。因此，它们是评估负荷控制有效性的重要因素。通过对这些工况的研究，可以扩展所研究的载荷工况范围，并对风力涡轮机整个寿命期内的总体载荷有更真实的了解。只有在前两个项目阶段完成的研究和规范扩展才能实现新的目标。此外，在此期间进行的模拟现在可以用于比较目的。为了验证新的扩展，风洞测量再次是必要的，因此，实验和模拟之间的密切联系将继续存在。

The common purpose of the research focus is the improvement of calculation methods for wind turbines in turbulent atmospheric inflow, the investigation of the occurring complex interactions and load cycles, the experimental and numerical study of a novel load alleviation concept and its influence of the aerodynamics of the turbine, the loads and the wake.The first main objective in the proposed prolongation phase (36 months) for the present sub-project is the extension of the numerical setup and process chain for CFD simulations of wind turbines with kinematically coupled leading and trailing edge flaps under turbulent inflow conditions. This will be done by implementing a fluid-structure coupling to determine the transient flap deflection, considering all acting forces, instead of prescribing them, as it was done up to now. The CFD code (FLOWer) will determine the unsteady aerodynamic forces and moments on the flaps and pass them to the CSD code (SIMPACK). There, the inertias and the weight forces will be calculated and the flap deflection will be determined. This will be done in a time-accurate manner for every physical time-step considered in the unsteady CFD simulation. To evaluate the load control concept under investigation and to study the occurring aerodynamic effects, the complexity of the system will be increased successively (starting from a 2D airfoil with leading edge and trailing edge flaps at steady inflow up to a full size wind turbine under turbulent atmospheric inflow conditions). The unsteady flap deflections will be calculated directly in all simulations. The extended process chain is verified by comparison with experimental data from two wind tunnel campaigns of profiles with load control concept and with wind tunnel data of a model rotor with load control. The validated code is then used to simulate the generic NREL 5MW wind turbine.The second main objective is the investigation of the influence of flaps for a turbine at non rated conditions. These operating conditions cause deterministic load fluctuations combined with unsteady aerodynamic effects, which were not investigated in the first two project phases but have a significant impact on the life time of a wind turbine. Therefore, they are an important element in the evaluation of the effectiveness of the load control. The studies of these cases lead to an extension of the scope of investigated load cases and to a more realistic view on the overall loads over the life time of a wind turbine.The new objectives can only be achieved thanks to investigations and code extensions done in the first two project phases. Moreover, the simulations performed during this time can now be used for comparative purposes. For the validation of the new extensions, wind tunnel measurement are necessary again and therefore, the close link between experiment and simulation will continue to exist.