球体状泥沙纵向相对暴露度概率密度分布

Probability density distribution of longitudinal relative exposure of spherical sediment

泥沙颗粒相对暴露度反映了泥沙在床面上的相对位置,它不仅直接影响着泥沙颗粒受力大小及滚动起动力臂大小,还可以间接改变颗粒周围水流结构,进一步影响颗粒受力大小及滚动起动力臂大小。通过自行设计的试验装置,测量了均匀球体泥沙绝对纵向暴露度,分析计算了纵向相对暴露度及其分布规律。结果表明,纵向相对暴露度可分解为x和y两个独立分量,其对应的取值区间分别为1~4.5和-1.5~1.5,且分量概率密度近似服从正态分布;纵向相对暴露度取值区间介于3.5×3的方形面域,区域内各点的概率密度也近似服从正态分布。对纵向相对暴露度的指数分布与正态分布进行了比较,结果表明,正态分布形式更适用于描述纵向相对暴露度的概率分布,计算值与实测值之间的误差较小。

The relative exposure degree of sediment particles reflects the relative position of sediment on the bed surface.It not only directly affects the force size of sediment particles and the size of the rolling incipient force arm,but also indirectly changes the flow structure around the particles.Further influence the force size of particles and the size of rolling incipient force arm.The absolute longitudinal exposure degree of uniform spherical sediment was measured by the self-designed experimental device,and the longitudinal relative exposure and its probability density distribution were calculated.Results show that the longitudinal relative exposure can be decomposed into two independent components as x and y,which corresponding value ranges are 1~4.5 and-1.5~1.5,and each component probability density approximately obey the normal distribution.The probability density of longitudinal relative exposure also approximates the normal distribution when the value of longitudinal relative exposure is belonged to a certain codomain determined by components of x and y.The exponential distribution of longitudinal relative exposure is compared with the normal distribution.The results show that the normal distribution is more suitable for describing the probability distribution of longitudinal relative exposure,and the error between the calculated value and the measured value is small.