天然河道水面线计算敛散性分析

天然河道水面线计算虽然理论上可以从计算流段上游或下游断面开始递推，但实际计算中从上游往下游递推时，经常遇到计算不收敛、无法推求的情况。本文从理论和计算方法两方面分析了产生这一现象的原因，分析了影响迭代的因素，如断面间距、河底比降对迭代计算产生的影响；同时本文也推导出形式简单的迭代算式，应用此算式计算黄河府谷段水面线．结果的论证了理论分析的合理性。

Astringency and divergency analysis of natural channel surface line calculation

Nature river course surface line calculation, theoretically,can be obtained from both upstream and downstream of the calculative section. In practice, when the calculation is carried through from upstream to down stream of the river, that the computation is not constringent may often encountered, and the result can not be reached. This paper analyzes reasons of this phenomenon from both theory and computational method, and finds out the factors that can affect the iteration computation. Meanwhile, this paper also deduces a relatively easy iterated mathematical formula and its astringency and divergency are discussed. Then this formula is applied actually to the water surface line calculation of Fugu reach in Yellow river, the results show rationalities of the theoretic analysis.