兰州大学机构库 >土木工程与力学学院
火星风沙流发展演化的数值研究
Alternative TitleNumerical studies on the evolution of wind-blown sand on Mars
傅林涛
Thesis Advisor郑晓静
2015-11-28
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword火星 风沙流 粒床随机碰撞 冲击启动临界风速 Bagnold focus 壁面剪切力 动力粗糙度 水平跃移速度 冲击速度 冲击角度
Abstract火星风沙运动对当前火星地表演化过程和大气辐射有着重要的影响。本学位论文首次提出了一个沙粒起跳初值不依赖实验得到的经验或半经验分布规律、可实时反映风沙流演化、且适用于不同环境的风沙流模型。相比于现有的风沙流模型,该模型具有以下三点创新:1) 将考虑冲击参数(速度和角度)对沙粒碰撞后速度恢复系数影响的粒-床随机碰撞模型引入到风沙流模型中,从而实现了沙粒起跳参数(速度和角度)的求解;2) 考虑到风沙运动中沙粒跃移速度与角度的关联,采用了角度-速度依赖的条件概率统计;3) 采用了包含来流风速、大气密度和粘性以及粒径的净风场中地表动力粗糙度表征。 应用新建立的模型本论文研究和分析了火星风沙流,并与地球上相应条件下的风沙流进行了比较。本论文首次揭示了火星和地球起跳和冲击速度分布定性上的差异、火星壁面剪切力随来流风速增大出现的反转的现象、火星上有着比地球更高比例的逆流向跃移运动、火星和地球上(中等及更大粒径沙粒)冲击角度随来流风速增加而增大的规律;给出了火星和地球稳定风沙流中的冲击启动临界风速、Bagnold focus所在的高度及该高度处对应的风速、动力粗糙度和跃移单宽输沙率的统一表征形式。
Other AbstractThe movement of wind-blown sand plays an important role in land surface processes and atmospheric radiation on Mars. This thesis put forward a numerical model of sand saltation, which adapts to various Aeolian surroundings. The model provides true and timely initial conditions for lift-off grains, which are no longer depending on semi-empirical or empirical results from existing theories or measurements as previous models did, with the evolution of wind-blown sand. With the help of the model, the evolution of wind-blown on Mars was investigated, and then compared with that on Earth. Some new results are obtained: different distribution laws of lift-off and incident velocities of saltating sand between on Mars and Earth, the reverse of surface shear stress with the increase of wind speeds on Mars, a higher proportion of backward saltation on Mars than that on Earth, and the rise of incident angle with the increase of wind speeds for medium and coarse sand on the two planets. Besides, some uniform expressions for physical quantities (e.g., impact threshold and sand transport rate) in wind-blown sand, which could be applied on both Mars and Earth, are found.
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226301
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
傅林涛. 火星风沙流发展演化的数值研究[D]. 兰州. 兰州大学,2015.
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