Abstract The momentum recovery downstream of a Vertical Axis Wind Turbine (VAWT) is analyzed as a function of its dynamic solidity, modified changing both the number of blades and the rotational speed of the turbine. Computations were carried out using Large-Eddy Simulations (LES), coupled with an Immersed-Boundary (IB) methodology. The streamwise increase of the momentum deficit in the near wake was found dominated by negative cross-stream advection, due to wake expansion, and especially negative pressure transport. Both of them were found larger at higher values of dynamic solidity. Downstream of the near wake region, the instability of the shear layers at both edges of the wake produced a substantial change of the wake topology and balance across momentum transport terms. The collapse of the shear layers into the wake core promoted wake recovery, via both positive cross-stream advection and turbulent transport. The destabilization of the wake system occurred earlier at larger values of dynamic solidity, producing this way a faster wake recovery, in spite of larger values of momentum deficit within the near wake. The switch to the wake of a bluff body was characterized by an increase of the energy at frequencies lower than that of the blades passage.

中文翻译：

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垂直轴风力涡轮机下游尾流恢复对其动态坚固性的依赖性

摘要 垂直轴风力涡轮机 (VAWT) 下游的动量恢复被分析为它的动态固体的函数，修改了叶片数量和涡轮机的转速。使用大涡模拟 (LES) 和浸入边界 (IB) 方法进行计算。由于尾流扩张，尤其是负压输运，近尾流中动量赤字的流向增加以负横流平流为主。在较高的动态坚固度值下，它们都被发现更大。在近尾流区域的下游，尾流两端的剪切层的不稳定性产生了尾流拓扑结构的重大变化和动量传输项的平衡。剪切层坍塌到尾流核心促进了尾流恢复，通过正横流平流和湍流传输。在较大的动态固体值下，尾流系统的不稳定发生得更早，从而以这种方式产生更快的尾流恢复，尽管近尾流内的动量赤字值较大。转向钝体尾流的特点是在频率低于叶片通过频率时能量增加。