【摘要】：黃河為舉世聞名的高含沙河流,在自然演變過程中,不僅沿垂向發(fā)生沖淤變化,在平面上也發(fā)生明顯的橫向擺動。本文選取黃河大柳樹河段為研究對象,該河段屬于隨來水來沙變化的彎曲性河道,主流擺動,沖淤變化大。擬建的大柳樹水庫位于甘肅與寧夏回族自治區(qū)交界處黃河干流黑山峽的出口處,是一項對西北經(jīng)濟欠發(fā)達地區(qū)和民族地區(qū)的工農(nóng)業(yè)生產(chǎn)和經(jīng)濟社會發(fā)展都具有十分重要意義的工程。結(jié)合河岸沖刷力學(xué)模式建立適合黃河大柳樹河段的三維水沙沖淤數(shù)學(xué)模型,對該河段建庫前的水流運動、泥沙沖淤及河岸擺動進行實測和數(shù)值模擬研究。利用一維、二維水溫數(shù)值模型模擬了黃河大柳樹水庫建成后壩下游河段及寧蒙河段冬季水溫分布情況和結(jié)冰點位置。其研究成果對大柳樹水庫的合理運行、減少淤積及對寧蒙河段的防凌提供可靠的理論依據(jù),具有重要的理論意義和工程應(yīng)用價值。建立基于非結(jié)構(gòu)網(wǎng)格下的三維紊流數(shù)值模型,利用非結(jié)構(gòu)網(wǎng)格有限體積法離散控制方程,并采用非結(jié)構(gòu)同位網(wǎng)格中的SIMPLE算法進行求解。對黃河沙坡頭河段連續(xù)彎道段的水流運動進行數(shù)值模擬,得到了平面流場分布、縱向流速沿垂線分布及橫向流速(二次流)的數(shù)值模擬結(jié)果,并與實測結(jié)果對比符合良好。驗證了該模型能夠較好地模擬具有復(fù)雜邊界的天然河流中彎道水流運動情況。在三維紊流模型的基礎(chǔ)上,綜合考慮河岸沖刷力學(xué)機理和河岸形態(tài)修正技術(shù),建立河床沖刷變化的三維水沙數(shù)學(xué)模型,利用該模型對黃河大柳樹河段的河勢變化情況進行了數(shù)值模擬研究。結(jié)果表明:模擬結(jié)果與實測結(jié)果吻合較好,說明本文建立的水沙數(shù)學(xué)模型能較好地反映黃河大柳樹河段的水流運動情況及河床變化規(guī)律。由于上游來水來沙條件不同,黃河大柳樹河段在2011年11月到2012年10月期間沖刷的同時還伴有橫向擺動。最大沖深可達2.5m左右,在彎道區(qū)域,凹岸沖刷較凸岸嚴(yán)重,深槽向凹岸擺動。表明彎道環(huán)流是河道橫向演變賴以實現(xiàn)的重要因素。建立了適合黃河大柳樹壩址下游及寧蒙河段的一維、二維水溫數(shù)學(xué)模型,模擬了冬季不同氣象條件下壩下游河段水溫分布情況及結(jié)冰點位置。預(yù)計黃河大柳樹水庫建成后,寧夏河段冬季各旬水溫均在0℃以上,零溫斷面位置將下移到石嘴山至磴口之間,距大柳樹壩址約320km。石嘴山至烏海段冰塞問題基本緩解,石嘴山至巴彥高勒河段將成為不穩(wěn)定封凍河段,巴彥高勒以下河段為穩(wěn)定封凍河段,昭君墳及以下河段冰情不會有明顯變化。大柳樹水庫的運用,對緩解寧蒙河段的凌情有著顯著的作用。
[Abstract]:The Yellow River is one of the most famous high sand bearing rivers in the world. In the process of natural evolution, not only the erosion and siltation along the vertical direction occurred, but also the lateral wobble occurred in the plane. In this paper, the Daliushu reach of the Yellow River is selected as the research object, which belongs to the curved channel with the change of incoming water and sediment, the main stream swinging and the scouring and silting changing greatly. The proposed Daliushu Reservoir is located at the exit of Heishan Gorge, the main Yellow River at the junction between Gansu and Ningxia Hui Autonomous region. It is a project of great significance to the industrial and agricultural production and economic and social development in the underdeveloped areas and ethnic areas of northwest China. Combined with the riverbank scour mechanics model, a 3D model of water and sediment scouring and silting was established for the Daliushu reach of the Yellow River. The flow movement, sediment scour and silt and riverbank swinging were measured and numerically simulated before the construction of the reservoir. Using one dimensional and two dimensional water temperature numerical model, the distribution of water temperature and the location of freezing point in the lower reaches of the dam and the Ningmeng reach after the completion of the Daliushu Reservoir on the Yellow River in winter were simulated. The research results provide a reliable theoretical basis for the rational operation of Daliushu Reservoir, reduce siltation and prevent the formation of the Ning-Meng River reach, and have important theoretical significance and engineering application value. A three-dimensional turbulent numerical model based on unstructured meshes is established. The control equations are discretized by the finite volume method of unstructured meshes and solved by SIMPLE algorithm in unstructured in-situ meshes. The numerical simulation of the flow movement in the continuous bend section of Shapotou reach of the Yellow River is carried out, and the numerical simulation results of the plane flow field, the vertical velocity along the vertical line and the transverse velocity (secondary flow) are obtained, which are in good agreement with the measured results. It is verified that the model can well simulate the movement of curved flow in natural rivers with complex boundaries. On the basis of three-dimensional turbulent model and considering the mechanism of riverbank scour mechanics and the technique of riverbank shape correction, a three-dimensional water-sediment mathematical model of riverbed scour change is established. The model is used to simulate the river regime variation in the Daliushu reach of the Yellow River. The results show that the simulation results are in good agreement with the measured results, which indicates that the mathematical model of water and sediment established in this paper can better reflect the flow movement of the Daliushu reach of the Yellow River and the variation law of the river bed. Due to the different conditions of water and sediment coming from the upper reaches of the Yellow River, the Daliushu reach of the Yellow River was washed from November, 2011 to October, 2012, and accompanied by lateral wobble at the same time. The maximum impact depth can reach about 2.5 m. In the bend area, the erosion of the concave bank is more serious than that of the convex bank, and the deep trough wobbles toward the concave bank. It is shown that the curved circulation is an important factor for the lateral evolution of the channel. A one-dimensional and two-dimensional water temperature mathematical model suitable for the lower reaches of Daliushu dam site and the Ningmeng reach of the Yellow River is established. The distribution of water temperature and the location of freezing point in the lower reaches of the dam under different weather conditions in winter are simulated. It is estimated that after the completion of the Daliushu Reservoir of the Yellow River, the water temperature of every ten days in the Ningxia reach will be above 0 鈩，

本文編號：2334646