垂直点阵集沙仪的集沙效率

垂直点阵集沙仪是挟沙气流中输沙量垂线分布测量的主要仪器，各类垂直点阵集沙仪的集沙效率有所不同，因而相应获取的实测资料之精度也差异较大，作者将大量实测输沙量垂线分布数据与获取这些数据的集沙仪类型相联系，分析了各类垂直点阵集沙仪的集沙效率。发现在近床面区各种集沙仪的集沙效率都较低提出了“集沙效率指标”。即用近床面区实测输沙量分布与上段输沙量确定的分布在近床面区外延计算值之间的偏离程度来反映各种集沙仪的集沙效率变化特征，在风速和沙粒粒径相似的条件下，集沙效率指标值越大，对应的集沙效率也越高，单管集沙仪的集沙效率最高，一般点阵式集沙仪的集沙效率次之，台阶式点阵集沙仪的集效率最低。集沙效率指标随集沙仪类型的变化主要受集沙仪中单个进沙口高度影响，反映了集沙仪内部排气状况的重要性。通过对气流速度和沙粒粒径等因素对集沙效率影响的讨论，提出了可以通过改善近床面区集沙条件，减小集沙进沙口高度等方法来提高集沙效率的建议，这些对进一步研制高效的集沙仅都具有参考价值。

Sampling Efficiency of Vertical Array Sand Traps

Numerous data have been obtained form vertical eolian sand|mass flux profiles by using a wide variety of vertical array sand traps.These data have not been used sufficiently because of different efficiencies for different types of traps.The comparison of the measured data from various traps indicated that the sand|collecting efficiencies of the traps are usually low and differ significantly for different traps in the near|bed region,whereas the efficiencies are high and are close for all kinds of traps in the upper region.The efficiencies of traps increase with height above the bed.Accordingly,the difference between trap efficiencies can be described by an index A that is used to express the extent of the deviation of sand|mass flux in near|bed region from the distribution calibrated in the upper region.Under the similar conditions of wind speed and sand grain size,the increase of the index A suggests the increase of the trap efficiencies.The index A computed from existing measured vertical profiles of mass flux of blown sand shows that the efficiency of single|tube trap is the highest,the efficiency of normal array trap the second,and the step|like array trap the last.The variation of index A may partly depend on the inlet height of chamber aperture of the traps,which indicates the importance of air outlet in traps.In addition,the effects of wind speed and sand grain size on trap efficiency were discussed,and some means for enhancing trap efficiency were pointed out.