不同来流条件下都江堰河段水流特性分析

Analysis on flow characteristicsof Dujiangyan Reach under various inflow conditions

本文采用平面二维数学模型模拟岷江都江堰河段内的水流运动,研究了不同来流条件下都江堰河段的水流特性,如内、外江与飞沙堰、宝瓶口分流比、都江堰河道断面平均流速和河道洪水位。模拟结果表明,内江的分流比与流量成正比,而外江的分流比则与流量成反比。这与常规认识的内、外江分流规律相悖。宝瓶口分流规律与实际观测情况相符,其分流比与流量成反比关系,并且其分流比例较低,保证成都平原的防洪安全。上游来流大小的改变对都江堰河道断面平均流速、洪水位影响不尽相同。每一级流量下的河道断面平均流速沿程变化规律基本一致;同一断面平均流速总体上随着来流流量的增大而增大;不同河段水位均随流量的增大而升高,但变化的幅度不同。

The flow movement of the Dujiangyan Reach is simulated herein with a 2 - D mathematical model for studying the flow characteristics of Dujiangyan Reach of Minjiang River, such as the flow diversion ratios of the Inner-river, the Outer-river and Feishayan Spillway, Baopingkou（which playsaroleof a diversion gate） , the average velocity of the section of Dujiangyan Reach, and the flood level of the channel. The simulation result shows that the diversion ratio of the Inner-river is proportional to its flow, while the diversion ratio of the Outer-river is inversely proportionalto its flow. This is contradictive to the law of the diversion be- tween both the Inner-river and the Outer-fiver in the conventional knowledge. The diversion law of Baopingkou coincides with its actually observed situation and its diversion ratio is inversely proportionalto its flow with a lower diversion proportion, and then ensures the safety of flood control of Chengdu Plain. The impacts from the changes of the amounts of the upstream inflows on the average flow velocity and flood level of the section of Dujiangyan Reach are not the same. The changing law of the average flow velocities along the reach section under all the levels of the flow rate are basically consistent, while the average flow velocity at an identical section is generally increased along with that of the inflow and the water levels of various river sections rise along with the enlargement of the flow rate with various changing ranges.