沙粒在草方格沙障内弥散特征的数值模拟

发布时间：2018-05-20 19:37

本文选题：草方格 + 风沙灾害　；参考：《兰州大学》2015年硕士论文

【摘要】：近年来以沙尘暴和土地荒漠化以代表的风沙灾害已经成为我国北方尤其是西北地区最主要的自然灾害,严重制约着当地经济和社会的可持续发展,开展风沙流的系统性研究和实施防风固沙工程是当下迫切的课题。草方格沙障因其很高的性价比而成为最具代表性的防风固沙工程,在我国西北地区得到大面积的推广应用,但目前对于草方格沙障的尺寸设计和固沙效能评估还没有科学的规范,草方格沙障的内流场的特征及沙粒的运动状况的研究依然比较欠缺。本文采用大涡数值模拟与离散粒子追踪法数值模拟了草方格沙障内流场的状态和沙粒在草方格沙障内的运动特征,并将部分结果与风洞实验相验证。流场运用流固两相耦合、空间平均的流体力学方程描述,湍流部分采用大涡模拟,颗粒相则采用拉格朗日离散单元法进行追踪。通过深入分析特征点处的风速、输沙率和颗粒速度,发现相比较无沙障时的输沙率,草方格沙障内的输沙率会大大的降低,证明草方格具有良好的阻沙固沙的功能。同时计算了整个风场的横向风速和沙障内颗粒速度,得到了风沙-耦合作用下的横向风速及其等值线图,清晰展现出草方格沙障内存在的非均匀分布的涡,这些涡所产生的回流使得沙障内一部分沙粒产生了负向的速度,涡的存在对沙粒在草方格沙障内的堆积分布有明显的影响。通过离散单元法追踪每颗沙粒的每一时刻的位置和速度,得到了沙粒在草方格沙障内的完整空间分布,动态模拟了草方格沙障阻沙固沙的整个过程。
[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.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S288;P425.55

【相似文献】