动床模型粒径比尺的确定方法

Determination methods of grain size scale of movable-bed model

中、细沙河床动床模型的基本相似条件为水流运动相似和泥沙运动相似。在水流运动相似条件中弗氏数相似和阻力相似的流速比尺形式不一致,且水流阻力是床沙粒径和水流强度的函数;在泥沙运动相似中有关粒径比尺形式也不一致,而且它们又与水流条件有关,错综复杂,使得泥沙粒径比尺的确定难度很大,不得不根据研究问题的性质对基本相似条件有所侧重和取舍,选取主要的作为设计依据,次要的允许有一定偏离。根据研究问题的需要,提出了粒径比尺设计方法,根据这些方法就可以确定出基本符合相似要求的泥沙粒径比尺。

The fundamental model similarity conditions are similarities of flow motion and sediment transport. In similarity of flow motion, the velocity scale in gravity similarity is not consistent with the one in resistance similarity, and the resistance is related to grain size and flow. The grain - size scales are not uniform in similarity of sediment transport, which are related to flow condition. Accordingly, the selection of the grain - size scale is very difficult. To meet the needs of practical problems, some emphases and choices of similarity condition are proposed, and some design methods as to grainsize scale are presented.