Sand fences are often erected to reduce wind speed, prevent aeolian soil focus our investigation on the behaviour of the near-surface wind shear velocity, which is defined here using a simple model based on wind speed values at height 20$\%$ of the fence height. Our simulations reveal novel insights about the three-dimensional structure of the turbulent wind flow between fences that are important for developing a theoretical description of this flow. We find that the area of soil associated with values of near-surface wind shear velocity that are below the minimal threshold for sand transport has two regimes, depending on the spacing $L_x$ between the fences. When $L_x$ is smaller than a critical value $L_{\mathit{xc}}$, the wake zones associated with each fence are inter-connected (regime A), while these wake zones appear separated from each other (regime B) when $L_x$ exceeds this critical value of spacing. The system undergoes a second order phase transition at $L_x=L_{\mathit{xc}}$, with the cross-wind width of the protected zone scaling with ${\left[1-L_x/L_{\mathit{xc}}\right]}^{\beta }$ in regime A, with $\beta \approx 0.32$. Moreover, we also perform a comparative investigation of arrays of constant and multiple fence heights on the basis of the two-dimensional shear velocity field obtained from our simulations. Our findings have implication for a better understanding of aeolian transport in the presence of sand fences, as well as to develop optimization strategies for measures to protect soils from wind erosion.

通常会竖起沙栅以降低风速，防止风沙土，我们将重点放在近地表风切变速度的研究上，此处使用基于高度20处的风速值的简单模型来定义$％$栅栏高度。我们的模拟揭示了关于栅栏之间湍流的三维结构的新颖见解，这对于建立这种流的理论描述非常重要。我们发现，与近地表风切变速度值相关的土壤面积低于沙粒运输的最小阈值，这取决于间距${\mathrm{大号}}_X$在栅栏之间。什么时候${\mathrm{大号}}_X$ 小于临界值 ${\mathrm{大号}}_{\mathit{c}}$，与每个围栏关联的唤醒区域是相互连接的（区域A），而当 ${\mathrm{大号}}_X$超过此间距的临界值。系统在以下位置经历了二阶相变${\mathrm{大号}}_X={\mathrm{大号}}_{\mathit{c}}$，保护区的侧风宽度按比例缩放 ${\left[\mathrm{1个}--{\mathrm{大号}}_X/{\mathrm{大号}}_{\mathit{c}}\right]}^{\beta }$ 在方案A中， $\beta \approx 0.32$。此外，我们还根据从我们的仿真中获得的二维剪切速度场，对恒定和多个围栏高度的阵列进行了比较研究。我们的发现对更好地理解在有沙栅栏的情况下的风沙运输，以及为保护土壤免受风蚀的措施制定优化策略具有重要意义。