求解峡谷河道边壁糙率的评述

本文是对于复合糙率n中分解出边壁糙率n_w方法的综合评述。各方法的基本关系式为n~(3/2)p=n~(3/2p_w+n_s~(3/2)p_o),首先说明这一关系式是唯一的解。利用水文测站的资料,点绘了γHJ为纵坐标、(2H/B-α)为横坐标的γHJ=τ_b+τ_w(2H/B-α)关系曲线,当2H/B大于α以后。边壁阻力才开始起作用。因(τ_w/ρ_o)~(3/2)=n_w/n_b,与基本关系式联解。可求得n_w和b_b(床面糙率)。介绍了利用垂线对数流速分布式U/U_*=Alog R_b/K_s+B求解n_b的方法。利用枯水位宽浅河道资料,忽略边璧阻力所建立的垂线流速分布式,求得n_b后,对求解所得n_w的误差,进行了估计。对于利用—个断面内高低两个水位,复合糙率n之差。来求解n_w也进行了评述。

A Review about the Side Wall Roughness Studies of Rivers in Gorges

The discussion on the methods to separate the side wall roughness coefficient m_w from the compound roughness n is given in this paper. Firstly, the basic equation (6), n~(3/2)P=n_w~(3/2)P_w+n_b~(3/2)P_b. used in all methods is proved to be the one and only ond solution.Secondly, using the measured data from the gauging stations, the relations γHJ=τ_b+τ_w(2H/B-α)are ploted with γHJ as ordinate against (2H/B-α)as abscissa. Only when 2H/B is greater than α, the side wall roughness is effective. Since (τ_w/τ_b)~(2/3)=(n_w/n_b) are known from the hydrologic measured data, and by simultaneously solving this relation with Basic Eguatin(6), the solution of n_b and n_w can be obtained.Other methods, such as the n_b obtained by the vertical velocity distribution, U/U_*=A log R_b/k_3+B is recommended. As the velocity distribution equation is obtained from the data of low water stage with sufficient width, neglecting the side wall resitance, the introduced error of n_w is discussed and estimated after the value n_b is calculated from the equation.The method of subtracting the compound roughness coefficients n of the high water stage by the low water stage to solve for n_w is presented with discusion.