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来流中风力机的计算方法，研究发生的复杂相互作用和载荷循环，实验和数值研究一种新的减载概念及其对涡轮机空气动力学、载荷和尾流的影响。本子项目拟议的延长阶段(36个月)的第一个主要目标是扩展湍流来流条件下具有运动耦合前缘和后缘襟翼的风力机的CFD数值模拟的数值设置和过程链。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，而不是像目前所做的那样规定它们。CFD程序(FLOW)将确定襟翼上的非定常气动力和力矩，并将它们传递给CSD程序(SIMPACK)。在那里，将计算惯性和重量的力量，并将确定襟翼偏转。对于非定常CFD模拟中考虑的每个物理时间步长，这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发生的空气动力效应，系统的复杂性将依次增加(从稳定进气时具有前缘和后缘襟翼的二维翼型到湍流大气进气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挠度。通过与带负荷控制概念的型材风洞试验数据和带负荷控制的模型转子风洞试验数据的对比，验证了扩展过程链的有效性。然后用验证后的程序对普通NREL 5 MW风力机进行了模拟。第二个主要目标是研究非额定工况下襟翼对风力机的影响。这些运行条件会导致确定性的负荷波动和非定常气动效应，这在前两个项目阶段没有得到研究，但对风力涡轮机的寿命有很大影响。因此，它们是评价负荷控制效果的一个重要因素。对这些案例的研究扩大了所调查的负载案例的范围，并使人们对风力涡轮机使用寿命内的总体负载有了更现实的看法。只有在前两个项目阶段进行调查和代码扩展，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.