NREL 5MW wind turbine blade and tower degradation

Problem ➔Track the degradation of one rotor blade and tower base over over as 10 months period under wind inflow and operational uncertainties Scenario ➔Continuous wind turbine blade and tower stiffness degradation, emulating blade root delamination resulting in dynamic instability, leading to the tower base excess fatigue. Simulation environment and setup in FAST v8 : ➔In the blade input file: modify flap and edge stiffnesses in damage regions, blade root (only 1 in 3 blades is affected). Assumed equal degradation in both edgewise and flapwise directions ➔In the blade input file: modify mode shapes coefficients (1st flap, 2nd flap and 1st edge modes) ➔In the tower input file: modify FA and SS stiffnesses in damage regions, tower base ➔In the tower input file: modify mode shapes coefficients (1st & 2nd FA and 1st & 2nd SS modes) ➔Note that the tower degradation only "shows up" in the last 2 monitoring periods ➔In the turbulence input file: modify wind speed, tuburlence intensity, shear exponent, horizontal and vertical inflow angles. ➔Further complication by assuming that the average input environmental conditions are not stationary over the monitoring period, emulating seasonal variations. ➔This means 120 environmental samples (and consequenly input wind field time series) are sampled from different distributions each period during the degradation process研究课题 ➔在来流风与运行不确定性条件下，追踪10个月周期内单支转子叶片及塔架基础的退化过程 试验场景 ➔模拟因叶片根部分层引发动态失稳、进而导致塔架基础过度疲劳的风力发电机组叶片与塔架连续刚度退化过程 FAST v8 仿真环境与设置： ➔叶片输入文件：修改叶片根部损伤区域的挥舞（flap）与摆振（edge）刚度，仅3支叶片中的1支受影响；假设摆振与挥舞方向的退化程度一致 ➔叶片输入文件：修改振型系数（第1阶挥舞、第2阶挥舞与第1阶摆振振型） ➔塔架输入文件：修改塔架基础损伤区域的迎风（FA）与侧风（SS）刚度 ➔塔架输入文件：修改振型系数（第1、2阶迎风振型与第1、2阶侧风振型） ➔注：塔架退化仅在最后2个监测周期内显现 ➔湍流输入文件：修改风速、湍流强度、剪切指数以及水平与垂直来流角 ➔进一步增设复杂性约束：假设监测周期内平均输入环境条件非平稳，以模拟季节变化 ➔这意味着在退化过程的每个监测周期，均从不同分布中采样得到120组环境样本（及对应的输入风场时间序列）