风洞边界层内单细长柔性植株周围地表气流剪应力分布特征

doi:10.7522/j.issn.1000-694X.2023.00020

摘要/Abstract

摘要：

地表剪应力表征了风对地表产生的剪切效应，是评估地表风蚀强度的风动量指标。研究植株周围地表剪应力分布特征对理解植被的防护效应有着重要意义。采用地表剪应力测试系统测量了风洞边界层中单个细长柔性植株周围地表剪应力及分布趋势。结果表明：从植株上风向到下风向，地表所受的气流剪切应力先减小而后逐渐增加至来流地表剪应力的数值；沿植株两侧方向，地表剪应力逐渐减小至来流地表剪应力的数值。与圆木棒模型相比，植株周围最小地表剪应力是圆木棒的0.51~0.74倍，并且地表剪应力小于来流值90%的平均面积是圆木棒的9.7倍。应用地表剪应力分布对单植株抗风蚀能力的评估表明细长柔性植株能减弱输沙率，比圆木棒模型更能有效地保护地表。

关键词: 地表剪应力, 柔性植株, 刚性圆木棒, 风洞边界层

Abstract:

Surface shear stress reflects the shearing effect of wind on the surface， which is a wind momentum index to evaluate the intensity of wind erosion. Study on the characteristics of surface shear stress distribution around a plant is of great significance for understanding the protective effect of vegetation. In this paper， the surface shear stress measurement system is used to measure the surface shear stress distribution around a single slender flexible plant in the wind tunnel boundary layer. The results show that from the upwind direction to the downwind direction of the plant， the surface shear stress first decreases and then gradually increases to the incoming value. Along the two sides of the plant， and the surface shear stress gradually decreases to the incoming value. Compared with the round stick model， the minimum surface shear stress around the plant is 0.51-0.74 times that of the round stick， and the average area where the surface shear stress is less than 90% of the incoming value is 9.7 times that of the round stick. The evaluation of wind erosion resistance by using the distribution of surface shear stress shows that the slender flexible plant can weaken the sand transport rate and protect the surface more effectively than the round stick model.

Key words: surface shear stress, flexible plant, rigid round stick, wind tunnel boundary layer

中图分类号:

X169

亢力强, 张琴, 张萌. 风洞边界层内单细长柔性植株周围地表气流剪应力分布特征[J]. 中国沙漠, 2023, 43(4): 128-134.

Liqiang Kang, Qin Zhang, Meng Zhang. Characteristics of surface shear stress distribution around a slender flexible plant model in wind tunnel boundary layer[J]. Journal of Desert Research, 2023, 43(4): 128-134.

图/表 8

图1 细长柔性植株模型

Fig.1 The slender flexible plant model

图2 柔性植株（A）和圆木棒（B）周围地表剪应力测点位置

Fig.2 Positions of measurement points of surface shear stress around flexible plant （A） and rigid round stick （B）

图3 细长柔性植株和刚性圆木棒周围地表剪应力分布的比较（黑色圆点为模型位置，uf0为来流风速，h为植株模型静止高度，τs为地表剪应力）

Fig.3 Comparison of surface shear stress distribution around slender flexible plant and rigid round stick （The black dot is the position of plant model， uf0 is the incoming wind speed， h is the height of plant model in still air， τs is the surface shear stress）

图4 细长柔性植株和刚性圆木棒周围地表剪应力减小区域（A）和增加区域（B）的比较（τs0为来流地表剪应力，τs/τs0为局部地表剪应力与来流地表剪应力的比值）

Fig.4 Comparison of areas of decreased （A） and increased （B） surface shear stress between slender flexible plant and rigid round stick （τs0 is the incoming surface shear stress， τs/τs0 is the ratio of local surface shear stress to the incoming surface shear stress）

图5 细长柔性植株和刚性圆木棒侧向地表剪应力的比较（流向位置为x=0 cm）

Fig.5 Comparison of surface shear stress on the sides of slender flexible plant and rigid round stick （x=0 cm）

图6 细长柔性植株和刚性圆木棒前后地表剪应力的比较（横向位置为y=0 cm）

Fig.6 Comparison of surface shear stress upwind and downwind of slender flexible plant and rigid round stick （y=0 cm）

图7 地表剪应力与1 cm高度处风速的关系

Fig.7 Relationship between surface shear stress and wind speed at 1 cm height

图8 细长柔性植株和刚性圆木棒的输沙率减弱程度的比较

Fig.8 Comparison of reduced degree of sand transport rate between slender flexible plant and rigid round stick

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