We present a computational fluid dynamic analysis of boundary layer transition on leading edge inflatable kite airfoils used for airborne wind energy generation. Because of the operation in pumping cycles, the airfoil is generally subject to a wide range of Reynolds numbers. The analysis is based on the combination of the shear stress transport turbulence model with the transition model, which can handle the laminar boundary layer and its transition to turbulence. The implementation of both models in OpenFOAM is described. We show a validation of the method for a sailwing (ie, a wing with a membrane) airfoil and an application to a leading edge inflatable kite airfoil. For the sailwing airfoil, the results computed with transition model agree well with the existing low Reynolds number experiment over the whole range of angles of attack. For the leading edge inflatable kite airfoil, the transition modeling has both favorable and unfavorable effects on the aerodynamics. On the one hand, the aerodynamics suffer from the laminar separation. But, on the other hand, the laminar boundary layer thickens slower than the turbulent counterpart, which, in combination with transition, delays the separation. The results also indicate that the aerodynamics of the kite airfoil could be improved by delaying the boundary layer transition during the traction phase and tripping the transition in the retraction phase.

中文翻译：

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前缘充气风筝翼型的边界层过渡建模。

我们提出了用于机载风能发电的前缘充气风筝翼型的边界层转变的计算流体动力学分析。由于在泵循环中运行，翼型件通常要承受很大范围的雷诺数。该分析基于剪应力传递湍流模型与过渡模型的结合，可以处理层流边界层及其向湍流的过渡。描述了两种模型在 OpenFOAM 中的实现。我们展示了该方法对帆翼（即带有薄膜的机翼）翼型的验证以及在前缘充气风筝翼型上的应用。对于帆翼翼型，在整个攻角范围内，利用过渡模型计算的结果与现有的低雷诺数实验吻合良好。对于前缘充气风筝翼型，过渡建模对空气动力学既有有利的影响，也有不利的影响。一方面，空气动力学受到层流分离的影响。但另一方面，层流边界层的增厚速度比湍流边界层慢，这与过渡相结合，延迟了分离。结果还表明，通过在牵引阶段延迟边界层过渡并在回缩阶段停止过渡可以改善风筝翼型的空气动力学性能。