河流动床阻力影响参数分析及其计算研究

动床阻力计算对河流研究和工程问题解决十分重要。自20世纪中叶起利用现代水力学知识计算动床阻力的方法陆续出现,本文对现有成果进行了分析评述,并对经典的Einstein和钱宁等阻力计算方法进行剖析,发现基于水力半径分割假说建立的动床阻力算法,不适用于研究主要由悬移质输沙强度决定床面形态的水流阻力问题。为此,本文首先选取有代表性的基本物理量,同实测糙率值进行相关性分析,确定出主参数;通过数据分析确定水深和能坡的指数后,运用造床流量下床沙中值粒径公式计算河床比降;基于能坡I计算需体现河床比降主导影响的同时应考虑边岸局部水头损失作用的认识,给出能坡修正式,再引入能体现沙粒和含沙量对动床摩阻的影响的因子,建立了动床阻力计算新方法。大量实测资料验证结果表明,本文公式计算精度高,适用性强。

Parameter analysis and calculation method of moving bed resistance

The calculation method of movable bed resistance is very important to the study of river dynamics and the solution of engineering problems. Since the middle of the 20th century, methods for calculating the resistance have appeared one after another. In this paper, the existing research results are described, and the classical Einstein and Qian Ning(N. Chien)resistance calculation methods are analyzed in detail. It is found that the calculation method of movable bed resistance based on hydraulic radius split hypothesis is not suitable for the bed form which is mainly determined by suspended load sediment transport intensity. Therefore, this paper firstly selects representative physical quantities and carries out correlation analysis with measured roughness values to determine the main parameters. The indexes of water depth and energy slope are determined by data analysis. The energy slope is mainly composed of riverbed gradient and local head loss, the gradient of riverbed is calculated by using the formula of median size of bed load under dominant discharge. The introduction of vortices parameter can reflect the influence of sediment content on movable bed resistance. In conclusion, a new method for calculating the resistance of movable bed is established. Verification results of a large number of measured data show that the formula in this paper has high calculation accuracy and strong applicability.