發(fā)布時(shí)間：2018-06-02 03:09

  本文選題：阻水障礙物群 + 透水密度系數(shù)�。� 參考：《浙江大學(xué)》2014年碩士論文

【摘要】：實(shí)際情況下,洪水在演進(jìn)過(guò)程中會(huì)不可避免地會(huì)遇到阻水障礙物群(如植被群和建筑群等),阻水障礙物群的存在對(duì)洪水運(yùn)動(dòng)和泥沙輸移都有很大的影響。本文通過(guò)引入透水密度系數(shù)以考慮阻水障礙物群對(duì)洪水運(yùn)動(dòng)過(guò)程中水流通量的影響,建立了二維動(dòng)力波洪水和泥沙運(yùn)動(dòng)數(shù)值模型,通過(guò)對(duì)不同情況下帶有阻水障礙物群的洪水演進(jìn)和泥沙運(yùn)動(dòng)進(jìn)行模擬分析,主要研究成果和結(jié)論如下： (1)分析總結(jié)了植被群和建筑群作為阻水障礙物群在洪水運(yùn)動(dòng)過(guò)程中的阻力作用,植被群在單位體積上的阻力可以表示為植被群對(duì)水流的阻力會(huì)因植被自身特性(剛性,柔性,有無(wú)樹(shù)葉)的不同而變化；而建筑物群在單位體積上的阻力為阻力會(huì)因建筑物分布的疏密程度以及形狀尺寸的不同而變化。 (2)在二維淺水運(yùn)動(dòng)和泥沙輸移方程的基礎(chǔ)上引入透水密度系數(shù)以綜合考慮阻水障礙物群對(duì)水流通量和泥沙輸移通量的影響,從而建立一個(gè)新的基于透水密度系數(shù)法的二維動(dòng)力波洪水和泥沙運(yùn)動(dòng)數(shù)值模型。同時(shí),模型還考慮了水流的粘性和紊動(dòng)擴(kuò)散作用,以及考慮地形變化影響的水沙耦合作用。本模型采用中心迎風(fēng)格式求解單元界面上的流量和動(dòng)量通量,并結(jié)合對(duì)界面變量的線(xiàn)性重構(gòu),使其具有空間上的二階精度。單元界面上的泥沙輸移通量采用迎風(fēng)格式進(jìn)行求解。為保證模型的和諧性和穩(wěn)定性,底床坡度項(xiàng)采用中心差分法離散,底床摩擦項(xiàng)和障礙物的阻力項(xiàng)用半隱式法離散。粘性和紊動(dòng)擴(kuò)散項(xiàng),泥沙運(yùn)動(dòng)擴(kuò)散項(xiàng)均采用中心差分格式處理。當(dāng)庫(kù)朗特?cái)?shù)滿(mǎn)足條件時(shí),模型能保證計(jì)算水深在任何時(shí)刻是非負(fù)的,使得模型具有良好的穩(wěn)定性。 (3)模型分別對(duì)帶有不同類(lèi)型阻水障礙物群的定床洪水算例進(jìn)行驗(yàn)證分析,結(jié)果表明：透水密度系數(shù)法可以將阻水障礙物群視為一個(gè)整體考慮,配置相同的計(jì)算參數(shù),網(wǎng)格劃分的疏密對(duì)透水密度系數(shù)法下的模擬結(jié)果影響較小,而設(shè)定高程法受網(wǎng)格粗細(xì)影響十分顯著。在計(jì)算精度和誤差相近的范圍內(nèi),相比設(shè)定高程法,透水密度系數(shù)法具有較高的計(jì)算效率,計(jì)算耗時(shí)僅為其1/50,這表明在洪水演進(jìn)數(shù)值模擬中,透水密度系數(shù)法比設(shè)定高程法更具優(yōu)勢(shì),這對(duì)于洪水風(fēng)險(xiǎn)評(píng)估和快速防災(zāi)決策極為重要。 (4)通過(guò)算例對(duì)考慮水沙耦合作用的洪水和泥沙運(yùn)動(dòng)數(shù)值模型進(jìn)行驗(yàn)證,分析其水動(dòng)力特征、泥沙運(yùn)動(dòng)以及河床變形特征,并利用該模型對(duì)阻水障礙物群—水生植被群影響下的洪水和泥沙運(yùn)動(dòng)進(jìn)行計(jì)算模擬,分析探討水生植被群的存在及其分布方式對(duì)洪水運(yùn)動(dòng)、泥沙輸移及底床沖淤的影響。結(jié)果表明：水生植被群的存在雖能有效減小上游河床的沖刷,但由于不利于過(guò)流,會(huì)使上游水位抬高而增加洪災(zāi)風(fēng)險(xiǎn)。同時(shí)分析了不同的植被群分布方式對(duì)洪水運(yùn)動(dòng)和泥沙輸移特性的影響,結(jié)果表明：植被區(qū)沿邊岸分布、寬度減半的方式是既能減小洪災(zāi)風(fēng)險(xiǎn)又能維持生態(tài)穩(wěn)定的較為有效的措施。
[Abstract]:In the actual situation, water hindrance barrier group (such as vegetation and building group) will inevitably be encountered during the process of flood evolution. The existence of water hindrance barrier group has great influence on flood movement and sediment transport. In this paper, the permeability density coefficient is introduced to consider the shadow of water barrier group on the flow flux during the flood movement. The numerical model of two dimensional dynamic wave flood and sediment movement is set up. The flood evolution and sediment movement in different cases are simulated and analyzed. The main research results and conclusions are as follows:
(1) the resistance of the vegetation group and the building group as the water hindrance barrier in the flood movement is analyzed and summarized. The resistance of the vegetation group on the unit volume can be expressed as the variation of the resistance of the vegetation group to the water flow due to the characteristics of the vegetation itself (rigid, flexible, and without leaves), and the resistance of the building group to the unit volume is the resistance of the building group. Resistance will vary depending on the degree of density and size of the building.
(2) on the basis of the two-dimensional shallow water movement and sediment transport equation, the permeability density coefficient is introduced to comprehensively consider the influence of the water barrier group on the flow flux and the sediment transport flux, thus a new numerical model of two-dimensional dynamic wave flood and sediment transport based on the permeable density coefficient method is established. This model uses the central upwind scheme to solve the flow and momentum flux on the interface, and combines the linear reconstruction of the interface variables to the two order accuracy in space. The sediment transport flux on the interface is used in the windward format. In order to ensure the harmony and stability of the model, the slope term of the bottom bed is discrete by the central difference method, the friction term of the bottom bed and the drag of the obstacle is separated by the semi implicit method. The viscous and turbulent diffusion term, the sediment movement diffusion term are all treated by the central difference scheme. When the kumatt number satisfies the condition, the model can guarantee the time to calculate the depth of water depth. Carving is nonnegative and makes the model stable.
(3) the model is verified and analyzed for the fixed bed flood calculation with different types of water obstructing obstacles. The results show that the permeable density coefficient method can consider the obstruction of water barrier as a whole consideration, with the same calculation parameters, and the density of grid partition has little influence on the simulation results under the permeable density coefficient method, and the set height is high. In the range of calculation accuracy and error, the pervious density coefficient method has a higher calculation efficiency compared with the set height method, and the time of calculation is only 1/50. This shows that the permeability density coefficient method is more advantageous than the set elevation method in flood evolution numerical simulation, which is the evaluation of flood risk. And rapid disaster prevention decisions are very important.
(4) through a numerical example, the numerical model of flood and sediment movement considering the coupling of water and sediment is verified, and its hydrodynamic characteristics, sediment movement and river bed deformation characteristics are analyzed, and the model is used to simulate the flood and sediment movement under the influence of water barrier group - aquatic vegetation group, and the existence of aquatic vegetation group is analyzed and discussed. The results show that the existence of the aquatic vegetation can effectively reduce the erosion of the upstream river bed, but the water level will be raised to increase the flood risk. The results show that the way to reduce the width of the vegetation along the shore and the width of the vegetation area is a more effective measure to reduce flood risk and maintain ecological stability.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TV122;TV14

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