挟沙气流中输沙量垂线分布的实验研究

Vertical Profiles of Sand-Mass Flux in Wind Tunnel

为了克服传统的垂直集沙方法在近床面区测量精度较低的缺陷 ,本文将垂直集沙方法和水平集沙方法结合 ,在风洞内测量了气流中输沙量沿垂线的分布 ,同时对沙粒沿风洞轴向的水平降落量进行了量测。实验分别针对五种风速条件和两种沙粒级配条件进行。结果表明 :挟沙气流中输沙量沿垂线分布的上段符合传统的指数递减分布规律 ,近床面区的输沙量较对应的指数分布函数预测值偏大 ,偏大的程度随气流摩阻速度和沙粒粒径的增大而减小。采用本文的实验方法可以半定量地揭示近床面区输沙量偏离指数递减分布规律的原因 ,并能够合理地概括以往关于近床面区输沙率测量精度研究的各个方面的论述。

Existing experimental results for vertical profiles of mass flux of blown sand have shown quite different patterns in the near\|bed region.To investigate these patterns and their formation cause,series of experiments were conducted for vertical and longitudinal profiles of mass flux using vertical array traps together with the horizontal sand trap composed of internal compartments in a wind tunnel.Five wind velocities and two particle sizes were chosen for a variety of experimental runs.Results show the satisfactory agreement of the measured profiles with the exponential decay distribution in the upper region but the deviation from the conventional law in the near\|bed region.The extent of the deviation decreases with the increase of airflow shear velocity and sand grain diameter in air.Explanations were given to the cause of deviation in terms of sand motion characteristics,whereas the trend estimation of the deviation was made based on the longitudinal decay distribution measured by means of the horizontal sand trap.