Measurement of wall shear stress in wind-blown sand environment
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摘要: 地表剪切力是风沙运动的关键驱动力，在风沙运动研究中非常重要，但目前针对风沙流环境地表剪切力的实验测量却较为匮乏，已经成为风沙运动研究深入发展的瓶颈。本文介绍了一种基于热膜技术的适用于风沙流环境地表剪切力精确测量的方法，使用热膜传感器和二维热线探头对净风条件下的地表剪切力进行了测量，结果显示：热膜传感器对地表剪切力有较好的响应，其与二维热线探头对摩阻风速的测量结果相差小于6.6%。热膜传感器对方柱绕流条件下地表剪切力的测量结果与OpenFOAM数值模拟结果具有较好的一致性，进一步证明了热膜传感器测量地表剪切力的可行性。热膜传感器的沙粒撞击实验结果表明：沙粒撞击对热膜信号的影响可以忽略，在风沙流环境中可以采用热膜传感器对地表剪切力进行有效测量。基于该技术测量了风沙流环境地表剪切力沿流向的空间分布特征，采用实测方式获得了风沙流环境地表剪切力的空间分布规律。Abstract: As a key driving force of aeolian sand movement, wall shear stress is of importance in the study of aeolian sand movement. However, at present, the experimental measurement of the surface shear force in the wind-blown sand environment is extremely scarce, which has become a bottleneck for the further development of the wind-blown sand research. This paper introduces a method based on the hot-film technology for accurate measurement of the wall shear stress in the wind-blown sand environment. The wall shear stress was measured under conditions without sand using hot-film probes and two-dimensional hot-wire probes, respectively. The result shows that the hot-film probe has a good response to the wall shear stress, and the difference between the measurement results of the friction velocity of these two probes is less than 6.6%. The measurement results of the hot-film probe for the wall shear stress of flow around the square column are in good agreement with the OpenFOAM numerical simulation results, which further proves the effectiveness of the hot-film probe for the measurement of the wall shear stress. In addition, the particle impact test results of the hot film probes show that the influence of particle impact on the hot-film signal is negligible, so the hot-film probe can be used to effectively measure the wall shear stress in the wind-blown sand environment. Based on this technology, the spatial distribution characteristics of the wall shear stress along the flow direction in the wind-blown sand environment were tested. And for the first time, the spatial distribution of the wall shear stress in the wind-blown sand environment was obtained by means of actual measurement. In view of the high-frequency response capability of the hot-film probe, this technology will play an important role in the experimental research on the mechanism of aeolian sand movement in the turbulent boundary layer.
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Keywords:
- hot-film probe /
- wind-blown sand /
- wall shear stress /
- two-dimensional hot-wire probe
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图 3 不同风速下热膜传感器的标定结果
Fig. 3 Calibration results of hot-film probes at different velociies
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图 5 沙粒撞击对热膜传感器测量结果的影响
Fig. 5 Effect of particle impact on measurement results of hot-film probe
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图 8 数值模拟中的地表剪切力分布
Fig. 8 Spatial distribution of wall shear stress in numerical simulation
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图 9 实验得到的方柱绕流摩阻风速与数值模拟结果对比
Fig. 9 Comparison between wind tunnel experiment and numerical simulation results of the friction velocity of flow behind a square column
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图 10 风沙流环境地表剪切力测量风洞实验示意图
Fig. 10 Schematic of measurement of wall shear stress in wind-blown environment
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