基于图像灰度的非均匀粉砂沉速试验研究

An image gray-based experimental study of settling velocity of nonuniform silt

该文总结了现有的沉速试验及测量方法,针对非均匀粉砂的特点,根据不同浓度泥沙浑水的透光差异性原理,提出了基于图像灰度的沉速试验方法。该方法通过连续拍摄图片记录泥沙沉降过程,将图片灰度值转化为浓度值得到垂向浓度分布,并根据质量守恒求解沉速。据此,进行了3组不同初始浓度的沉降试验,结果表明在0 kg/m3～2 kg/m3的浓度范围内,图像灰度与浓度的相关性较好。该方法与现有试验方法相比,减小了对粉砂沉降过程的干扰,可以合理地测量泥沙浓度和沉速的垂向分布及二者随时间的变化过程,并计算出三峡库区非均匀粉砂的平均沉速参考值,不足之处在于试验的条件不易控制和适用浓度较低。

The existing methods of sediment settling experiments and settling velocity measurement are summarized. According to the principle that the muddy water has different penetration capacity by light with different sediment concentration, an image gray-based experiment method of settling velocity is proposed in view of the characteristics of nonuniform silt. The sediment settling process are recorded through continuous image sampling, then the each image gray are transferred to obtain thevertical distribution of sediment concentration, the settling velocity will be calculated based on the sediment conservation equation. Calibration results show that the sediment concentration correlates the image gray well in the range of sediment concentration between 0 and 2 kg/m3. Results of three experiments illustrate that the new method can measure the vertical distribution of sediment concentration and settling velocity well, so are their variations with time. The average settling velocity of nonuniform silt sampled at the backwater region of Three Gorge Dam is also calculated through this method. Compared with the existing methods, the new method reduces the disturbance to the sediment settling process. However, the experimental conditions are of difficult control and the new method is applicable only to low sediment concentration.