Abstract.

Turbulent wind patterns over a two-dimensional isolated downsized barchan dune under the influence of sinusoidal inflow with different amplitudes and periods are simulated. The evolution rules of wind velocity over time at different positions are revealed. The flow reattachment distance and turbulence intensity distribution are also compared. The results show that wind velocities at different positions of the dune whose similar evolvement process of going from short-term fast adjustment transition to long-term stable sinusoidal fluctuation, can be reasonably estimated by the present simulation. It is found that, for the leeward toe of a dune with complex reversed flow, the balance position value of the sinusoidal wind velocity fluctuation is no longer close to the value of the steady wind velocity but shows a velocity deviation of about 0.40m/s. The flow reattachment distances under different unsteady inflows ultimately show a sinusoidal fluctuation with time, and their values are all larger than that of the steady flow. These synthetically predict that the unsteady flow has a stronger shaping effect on the leeward side of the dune body by enhancing sand transport. In addition, the predicted distribution comparison between unsteady wind velocity and turbulence intensity indicates that the unsteady wind velocity has a dominant effect on the turbulence intensity.

Graphical abstract

中文翻译：

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对固定隔离的小型沙丘上的单向非稳态振荡风的数值研究。

摘要。

模拟了正弦波流入下不同振幅和周期的二维隔离小尺度沙丘上的湍流风型。揭示了不同位置风速随时间的演变规律。还比较了水流的重新附着距离和湍流强度分布。结果表明，通过本模拟可以合理地估计沙丘不同位置的风速，其相似的演变过程从短期快速调整过渡到长期稳定的正弦波动。发现，对于具有复杂逆流的沙丘的背风脚趾，正弦风速波动的平衡位置值不再接近稳态风速的值，而是显示出约0.40m / s的速度偏差。在不同的非稳定流入下，流动的重新附着距离最终显示出随时间的正弦波动，并且它们的值都大于稳定流动的值。这些综合预测，通过增加沙的输送，非恒定流在沙丘体的背风侧具有更强的成形效果。此外，非稳态风速与湍流强度之间的预测分布比较表明，非稳态风速对湍流强度具有主要影响。

图形概要