复杂地形下风力机尾流数值模拟研究和激光雷达实验对比

CFD SIMULATION AND LIDAR EXPERIMENTAL STUDY ON WIND TURBINES IN COMPLEX TERRAIN

以CFD数值计算和实验相结合的方法,对处于中国西南某多山地区陆上风电场的尾流特性进行研究,验证不同数值方法在复杂地形的适用性。首先采用2台激光雷达,测量目标风力机一个月内的自由来流风速和尾流廓线,在地形上坡加速效应下,不同大气稳定度下目标风力机的自由来流风速廓线均呈负梯度。然后分别采用经典致动盘和改进致动盘法,模拟目标风力机在主风向下的尾流发展。不同于只有风速与压降关系的经典致动盘法,改进致动盘法更考虑了叶片几何和气动参数(尺寸信息、攻角、桨距角、升阻力系数等)。通过与后置激光雷达尾流测试结果对比,这2种基于CFD技术的数值模拟方法,计算网格相同,计算时间相当,且均能较好地模拟因为复杂地形而引起的尾流偏转;其中改进致动盘的尾流形状与激光雷达相似,速度亏损也更接近激光雷达结果。因此,改进致动盘法更适合于复杂地形条件下风场模拟,较好平衡了计算的效率与精度。

In this paper,the flow characteristics of an onshore wind farm with complex terrains in Southwest China was investigated with numerical and experimental methods. The applicability of different numerical methods in complex terrain is verified. Two lidars are vertically set down before and after the wind turbine. The free inflow wind speed and wake profile of the target wind turbine in one month were measured. It shows that,the wind speed profiles of the free inflow of the target turbines are all negative gradients under the acceleration effect of the terrain uphill. An improved actuator disk method is used,combined with blade information(such as geographical characteristics,attack angle,pitch angle),to simulate the wake precisely. Compared with classic AD method,the improved one fits the actual measurement much better. The study shows that the improved AD method can perform well in most complex terrains,especially in modelling what the velocity filed is like in a wake flow and how it is deflected by terrains. Moreover,it can be better balance between computational efficiency and accuracy.