Early laminar-to-turbulent transition due to fouling typically degrades the lift and amplifies the drag of airfoils. Few studies of medium-size horizontal and vertical axis wind turbines (HAWTs and VAWTs, respectively) provide information on this turbulence. This reflects uncertainties in the reported power coefficients (C_p) and contradictory recommendations for computational fluid dynamics (CFD) models. This paper investigates the C_p degradation of wind turbines (Re_chord = 0.7–1 × 10⁶) and its CFD-modeling aspects. Published experimental data for the modern DU12W262 airfoil, for both the clean and dirty surface conditions, are taken as the baseline. CFD is employed to reproduce airfoil characteristics for both cases. Using the blade element momentum and computational fluid dynamics (CFD) models, the experimental and numerical HAWT and VAWT performances are assessed. Non-transition turbulence closure models [Spalart–Allmaras and Shear Stress Transport (SST)], which have been recommended against in previous works without due consideration for surface aspects, are shown to successfully mimic dirty surface conditions but to underpredict the dramatic experimental degradation of 82% in maximum C_L/C_D to 67% when uncalibrated. The resulting experimental C_p reductions for HAWTs and VAWTs are 34% and 65%, respectively, values that are also underpredicted by CFD as 17% and 34%, respectively, without calibration. The detailed findings may serve as pioneering data for transition effects and aspects of CFD for both HAWTs and VAWTs at moderate Reynolds numbers.

中文翻译：

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中等雷诺数下基于升力的风力涡轮机边界层过渡效应和数值模拟的关键研究

由于结垢而导致的早期层流向湍流过渡通常会降低升力并放大翼型的阻力。对中型水平轴和垂直轴风力涡轮机（分别为HAWTs和VAWTs）的研究很少提供有关这种湍流的信息。这反映了报告的功率系数（C _p）的不确定性和计算流体动力学（CFD）模型的相互矛盾的建议。本文研究了风力涡轮机的C _p降级（Re _chord  = 0.7–1×10 ⁶）及其CFD建模方面。将现代DU12W262机翼在干净和肮脏的表面条件下发布的实验数据作为基准。两种情况下都使用CFD来重现翼型特性。使用叶片元件动量和计算流体动力学（CFD）模型，评估了HAWT和VAWT的实验和数值性能。非过渡湍流封闭模型[Spalart–Allmaras和剪切应力传输（SST）]在以前的工作中曾被建议不考虑表面因素而被推荐使用，它已成功模拟了肮脏的表面条件，但是低估了实验的剧烈退化。未校准时，最大C _L / C _D的82％至67％。产生的实验CHAWT和VAWT的_p降低分别为34％和65％，未经校准，CFD还将这些值分别低估为17％和34％。详细的发现可以作为中等雷诺数的HAWT和VAWT的过渡效应和CFD方面的先驱数据。