抛物线形复合渠道实用经济断面的计算方法

Method to Calculate Economic Cross-section of Parabolic Composite Channel

【目的】解决平方抛物线形渠坡和水平渠底的复合渠道水力最佳断面存在施工难度大、不经济等问题。【方法】在水力最佳断面的基础上,通过数据拟合的方式,得到了求解最佳H/H0值所对应的抛物线水面宽和水深比η=1.666,推导出了抛物线形复合渠道实用经济断面的计算公式,并提出了详细的计算步骤。【结果】通过实例计算,当流量Q为26 m3/s、n为0.015、i为0.000 52、α为1.03时,抛物线形复合渠道实用经济断面情况下的水深H为2.054 m,渠底宽度b为4.447 m,过水断面面积A为13.818 m2,湿周长度χ为10.037 m。在相同流量、糙率与渠道底坡条件下与梯形、弧形坡脚梯形相比,抛物线形复合渠道实用经济断面面积最小,比梯形减小了1.65%,比弧形坡脚梯形减小了1.29%。【结论】抛物线形复合渠道实用经济断面更为优越。

【Objective】Cross section is a parameter in channel design and this paper presents a method to calculate economic cross section of composite channel with parabolic cross section and flatten bottom.【Method】From the optimal hydraulic cross section and using curve-fitting against experimental data, we obtained the optimal H/H0 ratio the parabolic water surface width to water depth be η=1.666. We then derived a formula to calculate the economic cross section of the composite channel.【Result】When flow rate in the channel was Q=26 m^3/s and other parameters were n=0.015, i=0.000 52 and α=1.03, the water depth was H=2.054 m, the bottom width of the channel was b=4.447 m, the cross-section the water was A=13.818 m^2 and the wet length was χ=10.037 m.Under the same flow rate, roughness and slope ratio, the parabolic-shape composite channel had the smallest economic cross section, reduced 1.65% compared to the trapezoid and 1.29% compared to the arc-shaped foot trapezoid.【Conclusion】Parabolic composite channel is most economical.