柔性植株地表瞬时地表剪应力分布特征

doi:10.7522/j.issn.1000-694X.2020.00048

摘要/Abstract

摘要：

由于风的湍流性质，风对地表剪切作用而产生的地表剪应力是瞬态变化的。本文重点研究柔性植株地表植株周围瞬时地表剪应力的分布特征，为评估植株防风蚀作用提供参考。通过风洞实验，测量了在不同植株密度和不同来流风速下细长柔性植株覆盖地表上植株周围瞬时地表剪应力的空间分布。结果表明：柔性植株地表植株两侧地表剪应力增加，植株前后地表剪应力减小；随风速的增加，地表剪应力、均方根脉动地表剪应力的空间平均值和标准偏差均增加，而地表剪应力脉动强度的空间平均值和标准偏差均减小，它们在空间上的相对标准偏差基本不受风速的影响；随植株密度的增加，地表剪应力的空间平均值和标准偏差以及均方根脉动地表剪应力的空间平均值均减小，而地表剪应力在空间上的相对标准偏差、地表剪应力脉动强度的空间平均值和标准偏差均增大。

关键词: 瞬时地表剪应力, 柔性植株, 风洞实验

Abstract:

Surface shear stress caused by wind shear on the surface is instantaneous due to wind turbulence. This paper focuses on the study of distribution characteristics of instantaneous surface shear stress at the flexible plant surface in order to evaluate the plant protection against wind erosion. The space distribution of instantaneous surface shear stress at the slender flexible plant surface is measured at different plant densities and incoming wind speeds in a wind tunnel. The results show that the surface shear stress increases on both sides of the plant and decreases upwind and downwind of the plant. With the increase of incoming wind speed， the spatial mean value and standard deviation of surface shear stress and RMS surface shear stress fluctuation increase， while the spatial mean and standard deviation of fluctuation intensity of surface shear stress decrease， and their relative standard deviations in space are generally unaffected by wind speed. With the increase of plant density， the spatial mean value and standard deviation of surface shear stress decrease， and the spatial mean value of RMS surface shear stress fluctuation also decreases， while the relative standard deviation of surface shear stress in space and the spatial mean value and standard deviation of fluctuation intensity of surface shear stress increase.

Key words: instantaneous surface shear stress, flexible plant, wind tunnel experiment

中图分类号:

X169

亢力强, 李彩云, 张军杰, 邹学勇. 柔性植株地表瞬时地表剪应力分布特征[J]. 中国沙漠, 2020, 40(5): 49-56.

Liqiang Kang, Caiyun Li, Junjie Zhang, Xueyong Zou. Characteristics of instantaneous surface shear stress distribution at flexible plant surface[J]. Journal of Desert Research, 2020, 40(5): 49-56.

图/表 10

图1 风洞中的植株模型

Fig.1 Plant model in wind tunnel

图2 植株周围测点分布

Fig.2 Measurement points around the plant

图3 瞬时地表剪应力随时间的变化

Fig.3 Variation of instantaneous surface shear stress with time

图4 不同植株密度下地表剪应力分布的比较（气流方向从左到右）

Fig.4 Comparison of surface shear stress at different plant densities (air flows from left to right)

图5 地表剪应力的空间平均值、标准偏差和相对标准偏差随植株密度和来流风速的变化

Fig.5 Variation of mean value, standard deviation and relative standard deviation of surface shear stress in space with plant density and incoming wind speed

图6 均方根脉动地表剪应力的空间分布

Fig.6 Space distribution of RMS fluctuation of surface shear stress

图7 均方根脉动地表剪应力的空间平均值、标准偏差和相对标准偏差随植株密度和来流风速的变化

Fig.7 Variation of mean value, standard deviation and relative standard deviation of RMS fluctuation of surface shear stress in space with plant density and incoming wind speed

图8 地表剪应力脉动强度的空间分布

Fig.8 Space distribution of fluctuation intensity of surface shear stress

图9 地表剪应力脉动强度的空间平均值、标准偏差和相对标准偏差随植株密度和来流风速的变化

Fig.9 Variation of mean value, standard deviation and relative standard deviation of fluctuation intensity of surface shear stress in space with plant density and incoming wind speed

图10 测点a和b的瞬时地表剪应力概率密度分布

Fig.10 Probability density distribution of instantaneous surface shear stress at measurement points a and b

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