本文選題：草方格 + 風沙災害　； 參考：《蘭州大學》2015年碩士論文

【摘要】：近年來以沙塵暴和土地荒漠化以代表的風沙災害已經(jīng)成為我國北方尤其是西北地區(qū)最主要的自然災害,嚴重制約著當?shù)亟?jīng)濟和社會的可持續(xù)發(fā)展,開展風沙流的系統(tǒng)性研究和實施防風固沙工程是當下迫切的課題。草方格沙障因其很高的性價比而成為最具代表性的防風固沙工程,在我國西北地區(qū)得到大面積的推廣應用,但目前對于草方格沙障的尺寸設計和固沙效能評估還沒有科學的規(guī)范,草方格沙障的內(nèi)流場的特征及沙粒的運動狀況的研究依然比較欠缺。本文采用大渦數(shù)值模擬與離散粒子追蹤法數(shù)值模擬了草方格沙障內(nèi)流場的狀態(tài)和沙粒在草方格沙障內(nèi)的運動特征,并將部分結(jié)果與風洞實驗相驗證。流場運用流固兩相耦合、空間平均的流體力學方程描述,湍流部分采用大渦模擬,顆粒相則采用拉格朗日離散單元法進行追蹤。通過深入分析特征點處的風速、輸沙率和顆粒速度,發(fā)現(xiàn)相比較無沙障時的輸沙率,草方格沙障內(nèi)的輸沙率會大大的降低,證明草方格具有良好的阻沙固沙的功能。同時計算了整個風場的橫向風速和沙障內(nèi)顆粒速度,得到了風沙-耦合作用下的橫向風速及其等值線圖,清晰展現(xiàn)出草方格沙障內(nèi)存在的非均勻分布的渦,這些渦所產(chǎn)生的回流使得沙障內(nèi)一部分沙粒產(chǎn)生了負向的速度,渦的存在對沙粒在草方格沙障內(nèi)的堆積分布有明顯的影響。通過離散單元法追蹤每顆沙粒的每一時刻的位置和速度,得到了沙粒在草方格沙障內(nèi)的完整空間分布,動態(tài)模擬了草方格沙障阻沙固沙的整個過程。
[Abstract]:In recent years, the wind-sand disaster represented by sandstorm and land desertification has become the most important natural disaster in the north of China, especially in the northwest region, which seriously restricts the sustainable development of local economy and society. It is an urgent task to carry out systematic research on wind and sand flow and to implement wind and sand fixation engineering. Because of its high performance-price ratio, the grass square sand barrier has become the most representative project of wind and sand fixation, and has been widely used in northwest China. However, there is no scientific criterion for the size design and sand fixation effectiveness evaluation of the grass grid sand barrier, and the study of the characteristics of the inner flow field and the sand movement of the grass grid sand barrier is still lacking. In this paper, the large eddy numerical simulation and discrete particle tracing method are used to simulate the state of the flow field and the movement characteristics of sand particles in the grass square sand barrier. Some of the results are verified by wind tunnel experiments. The flow field is described by the hydrodynamic equation of space average, the turbulent part is simulated by large eddy, and the particle phase is tracked by Lagrangian discrete element method. By deeply analyzing the wind speed, sediment transport rate and particle velocity at the characteristic point, it is found that compared with the sand transport rate without the sand barrier, the sand transport rate in the grass grid sand barrier will be greatly reduced, which proves that the grass grid has a good function of preventing sand and sand fixation. At the same time, the transverse wind speed and particle velocity in the whole wind field are calculated, and the transverse wind speed and its contour diagram under the action of wind-sand coupling are obtained, which clearly shows the non-uniform distribution vortex in the grass grid sand barrier. The reflux produced by these vortices causes a negative velocity of some sand grains in the sand barrier, and the existence of the vortex has a significant effect on the accumulation and distribution of sand particles in the grass grid sand barrier. By tracing the position and velocity of each sand at every moment by means of discrete element method, the complete spatial distribution of sand particles in the grass grid sand barrier is obtained, and the whole process of sand fixation in the grass grid sand barrier is simulated dynamically.
【學位授予單位】：蘭州大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：S288;P425.55

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