冰封河道纵向离散系数计算研究

Study on longitudinal dispersion coefficient for ice-covered rivers

河道的封冻显著的改变了水流的流动结构和纵向离散特性。借助于根据天然河道特征概化的抛物线型断面型态,结合垂向双对数的流速分布律,建立了冰封河道全断面的流速分布;在此基础上研究了冰封河道中纵向流速横向分布不均匀性和垂向分布不均匀性对纵向离散的影响并建立了针对宽浅型冰封河道纵向离散系数的计算公式。公式以理论积分公式为基础,综合考虑了断面型态及冰盖的影响,机理清楚,形式简单,便于应用,且计算结果与示踪试验成果吻合良好,可以用来预测宽浅型冰封河道的纵向离散系数。

The presence of ice covers in a river causes a significant change in its longitudinal dispersion and flow structure. Cross-sectional velocity profiles of ice-covered natural rivers are established in this paper by assuming a parabolic shape of cross section and applying the logarithmic law of vertical distribution. Using these profiles, the effects of velocity non-uniformity on longitudinal dispersion coefficient are analyzed including the distributions in vertical and transverse directions, and a formula for predicting the coefficient for ice-covered rivers is derived. This formula is constructed from the triple integral technique and it takes into account the effects of cross-sectional shape and ice covers. With a solid theoretical basis and high accuracy, it can be used to calculate longitudinal dispersion coefficients of wide ice-covered rivers.