In the beginning of the 1980’s Large Eddy BreakUp (LEBU) devices, thin plates or airfoils mounted in the outer part of turbulent boundary layers, were shown to be able to change the turbulent structure and intermittency as well as reduce turbulent skin friction. In some wind-tunnel studies it was also claimed that a net drag reduction was obtained, i.e. the reduction in skin-friction drag was larger than the drag on the devices. However, towing-tank experiments with a flat plate at high Reynolds numbers as well as with an axisymmetric body showed no net reduction, but instead an increase in total drag. Recent large-eddy simulations have explored the effect of LEBUs on the turbulent boundary layer and evaluations of the total drag show similar results as in the towing tank experiments. Despite these negative results in terms of net drag reduction, LEBUs manipulate the boundary layer in an interesting way which explains why they still attract some interest. The reason for the positive results in the wind-tunnel studies as compared to drag measurements are discussed here, although no definite answer for the differences can be given.

中文翻译：

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大涡分离装置——从斯德哥尔摩地平线看 40 年

在 1980 年代初期的大涡分离 (LEBU) 装置中，安装在湍流边界层外部的薄板或翼型被证明能够改变湍流结构和间歇性，并减少湍流表面摩擦。在一些风洞研究中，还声称获得了净阻力减少，即皮肤摩擦阻力的减少大于设备上的阻力。然而，具有高雷诺数平板和轴对称体的拖曳水箱实验显示没有净减少，而是增加了总阻力。最近的大涡模拟探索了 LEBU 对湍流边界层的影响，总阻力的评估显示出与拖曳水箱实验相似的结果。尽管在净减阻方面有这些负面结果，LEBUs 以一种有趣的方式操纵边界层，这解释了为什么它们仍然引起一些兴趣。此处讨论了风洞研究与阻力测量相比获得积极结果的原因，尽管无法给出差异的明确答案。