基于非恒定水流模拟的灌区明渠水力响应特征分析

为了服务于石头河灌区信息化建设,该文以石头河灌区东干渠渠首约10 km渠道为研究对象,采用渠道非恒定流模拟方法以及闸门自动控制理论模拟分析不同边界条件下灌区渠道断面的水流和闸门开度变化特点,通过模拟分析获得研究渠段在不同水流控制情况下断面上水力响应变化特征规律:相同渠首流量变化条件下,距渠首距离越远断面水力响应持续时间越长;渠首流量变化率越大,相同断面上水力响应持续时间越短;当取水口取相同流量时,渠首稳定流量大小与取水口取水对干渠上游渠道断面水流的影响距离呈线性关系;渠首流量稳定在相同流量时,取水口取水流量大小与对干渠上游渠道断面水流的影响距离呈指数关系;在进行渠道流量控制时,取水初期取水口闸门调节比较频繁。由于渠道水流之间的相互影响,多个取水口同时进行取水,渠道任意取水口闸门开度变化,都可能引起其他闸门开度的调整。同时通过与实测资料进行对比验证,所获得的渠道断面水流响应特征规律与实际基本相符,模拟渠道水深值与实测水深值误差在±10 cm之间。该研究可为石头河灌区渠道信息化建设及水资源的优化配置提供科学依据。

Open channel hydraulic response characteristics in irrigation area based on unsteady flow simulation analysis

The informatization trend of irrigation area is to master real time hydraulic characteristics of canal sections based on which water distribution can be realized through controlling the gates automatically. In order to serve the information construction of the Shitouhe irrigation area, in this paper, we simulated and analyzed the canal flow and gate opening characteristics with the theory of unsteady flow and automation under different conditions along the 10 km long first reach of east main canal in the Shitouhe irrigation area. In the process of analysis, first of all, the whole canal was divided into several sections, and the sections were numbered from upstream to downstream; then the error of water depth between measured and calculated accordingly was minimized, which was used as the objective function for finding the roughness based on the calculation principle of the water surface curve of the open-channel constant gradual flow; at last we simulated and analyzed the canal flow and gate opening characteristics using different schemes under different boundary conditions and roughness coefficients obtained above. In terms of hydraulic response characteristics analysis under different conditions at canal head, 3 schemes were assumed, which were as follows: Scheme 1, the flow at canal head increased from 3.5 to 11.5 m3/s within 1, 10, 30 and 60 minutes respectively and then remained unchanged Scheme 2, the flow at canal head increased linearly from 3.5 to 5.5, 7.5, 9.5 and 11.5 m3/s within 10 minutes and then remained unchanged; Scheme 3: the flow at canal head varied following the sine curve within 60 minutes and after that remained at 3.5 m3/s unchanged with the maximum variation of 2.5 m3/s. In terms of hydraulic response characteristics analysis under canal water-intake flow, 2 schemes were assumed, and based on these schemes the solutions were: Scheme 1, canal head flow was stable at 3.5, 5.5, 7.5, 9.5 and 11.5 m3/s respectively, and at water intake of No.1 branch (at Section 72) take water according to design flow of 1.03 m3/s; Scheme 2, canal flow was stable at 11.5 m3/s, and at water intake of No.1 branch (Section 72) take water of 0.1, 0.2, 0.4, 0.6, 0.8 and 1.03 m3/s respectively. In terms of hydraulic response characteristics analysis of gate control, 2 schemes were assumed, based on which the solutions were: Scheme 1, the flow at canal head was stable at 11.5 m3/s, and at water intake of No.2 branch take water of 2.5 m3/s under gate control; Scheme 2, the flow at canal head was stable at 11.5 m3/s, at water intake of No.2 branch take water of 2.5 m3/s, and after 2.5 h at water intake of main 7 lateral take water of 0.2 m3/s. Through simulation and analyzation under the different conditions, the hydraulic response characteristics of the canal flow were got as follows: 1) When canal head flow changed, the flow would be changed later with the farther distance from the canal head, and flow along longitudinal direction would be flattened. 2) Under the same flow change rate, the time between starting to change and recovering to be steady would be longer when the distance from canal head was farther, but under different flow change rates, when the flow change rate was larger, the time between starting to change and recovering to be steady would be shorter at the same distance from the canal head. 3) Under different flow rate conditions at canal head, when canal intake flows were the same, the steady flow size exhibited a linear relation with the influence distance of intake flow on upstream stream; but when canal intake flows were different, the steady flow size exhibited an exponential relationship with the influence distance of intake flow on upstream stream. 4) Under steady flow condition at canal head, when individual intake gate was controlled and its opening operates frequently during initial period; when some intake gates were controlled, the opening of any intake gate would affect intake flows of the others, due to the intake flows' reciprocity. 5) By comparison, the simulated hydraulic response characteristics at canal sections were consistent with the measured ones, and the error of canal water depth was within ±10 cm. These may provide some basic knowledge for the safety operation in order to realize scientific allocation of water resources in an irrigation area.