三维旋转水平轴风力机流场的PIV试验和数值模拟

PIV Test and Numerical Simulation of 3-D Rotating HAWT in Laboratory Wind Tunnel

通过粒子图像测速仪(Particle image velocimetry,PIV)测量和定常计算流体力学(Computational fluid dynamics,CFD)数值模拟相结合的方法,对某三维旋转水平轴风力机模型的流场展开研究。在风洞开口实验段,来流风速为8m/s,针对不同尖速比(λ=4,8)利用PIV技术对风力机叶片的瞬时速度场进行测试。通过定常CFD数值模拟,获得了风力机叶片在相应工况下的流场细节。在8m/s来流风速下,当尖速比大于7.4时,试验测得的风轮扭矩和风能利用率与数值模拟结果趋于一致。尖速比小于7.4时,试验测得的扭矩值低于计算值,其风能利用效率也较低。通过速度矢量分布可以看出,在λ=4时,PIV测得靠近叶根的两个截面S1,S2在叶背有明显的流动分离,CFD结果中仅在S1截面叶背存在流动分离,S2截面叶背存在低速区。在λ=9.8时,PIV和CFD结果均显示叶片绕流流场没有流动分离。尝试采用Gamma Theta转捩模型进行了数值模拟,在考虑了层流影响后,计算所得风轮扭矩更加接近试验值。

A three-dimensional horizontal axis wind turbine model is tested and numerically studied.The test is carried out in a laboratory wind tunnel.With PIV measurement,the flow fields around the blade in varied rotating speed and wind speed are obtained.Furthermore,the test result is compared with CFD simulation to study the flow fields in more detail,especially the graphs of the velocity vector,under different operating conditions.The relatively good agreement between the test and numerical results is achieved in some conditions.Besides,under some conditions,the test results are different from the numerical ones.To find the reason of the difference,the numerical simulation with transition model is carried out.Results show that with a consideration of laminar flow and transition process,the calculated wind turbine torque is closer to the test value.