回顾了对暴露度的研究现状及存在的问题。提出了一种定义暴露度的方法及其计算式 ,同时得到了计算暴露度Δ及暴露度系数 ξ的表达式。经过分析 ,给出了 ξ的取值范围为 0～ 1,它随颗粒在床面的位置而变。同时提出了等效粒径的概念及其计算方法。并对不同粒径 ,在床面不同位置的暴露度、暴露度系数及等效粒径进行了计算。对非均匀沙 ,当相对暴露度系数一定时 ,大于平均粒径的泥沙颗粒的等效粒径较同等粒径均匀沙的等效粒径小 ,容易起动 ;小于平均粒径的颗粒较同等粒径均匀沙的等效粒径大 ,较难起动 ,等于平均粒径的颗粒与均匀沙等效粒径相当。经分析等效粒径是一种较符合实际的方法 ,且公式简单、使用方便 The research status and existing problems of exposure are reviewed. A method of defining the degree of exposure and its calculation formula are proposed. At the same time, an expression for calculating the exposure degree Δ and the exposure coefficient ξ is obtained. After analysis, the value of ξ is given as 0 ~ 1, which varies with the position of particles on the bed surface. At the same time, the concept of equivalent particle size and its calculation method are proposed. The different particle size, the exposure at different positions of the bed, the coefficient of exposure and the equivalent particle size were calculated. For non-uniform sand, when the relative coefficient of exposure is constant, the equivalent particle size of sediment particles larger than the average particle size is smaller than the equivalent particle size of uniform sand and easy to start; particles smaller than the average particle size The equivalent particle size of uniform sand large equivalent diameter, more difficult to start, equal to the average particle size of the particles and uniform equivalent diameter sand equivalent. The analysis of the equivalent particle size is a more realistic method, and the formula is simple and easy to use