风沙流跃移沙粒运动的若干基本问题 Alternative Title Some basic problems of saltating particles in wind-blown sand 张亚丽 Thesis Advisor 黄宁 2005-05-31 Degree Grantor 兰州大学 Place of Conferral 兰州 Degree Name 硕士 Keyword 风沙流 跃移沙粒 轴线风速 输沙率 Abstract "已有许多学者对起跳沙粒的初速度分布函数进行过研究。但这些研究主要考虑垂直方向的初速度分布，而忽略了沙粒起跳时的水平初速度分布。本文在对董治宝等人利用粒子动态分析仪在风洞中测得的起跳沙粒的初速度进行分析的基础上，拟合了考虑沙粒起跳水平速度及竖直速度的二维合初速度分布函数。在此基础上建立了稳态风沙跃移云数值模型，对不同轴线风速和粒径下风速和输沙率沿高度的分布及单宽输沙率进行了计算。并将计算结果与不考虑起跳沙粒水平初速度分布函数的结果进行了比较，结果表明沙粒起跳时其水平方向的速度分量的分布函数对风沙流中这些宏观量的影响不容忽视。 在现有风沙跃移运动的研究中，沙粒在空中的碰撞通常被忽略。本文利用概率统计原理以及风沙两相流数值计算，提出了一种计算跃移云中沙粒在空中发生碰撞概率的理论模型。模拟了不同轴线风速下以不同初速度起跳的跃移沙粒在上升阶段、下降阶段及整个跃移过程中发生碰撞的概率；同时用实验得到的起跳初速度分布函数，计算了不同轴线风速下随机起跳的跃移沙粒在空中发生碰撞的概率，比较了考虑风沙耦合和不考虑风沙耦合的结果。计算结果表明当轴线风速和起跳初速度足够大时，跃移沙粒在空中发生碰撞几乎是必然的。 " Other Abstract "Many scholars have researched the saltating particle’s lift-off velocity. But those study chiefly take account of the distribution of vertical lift-off velocity, and ignore the distribution of saltating particle’s horizontal velocity. In this article, we analysis the measurement data gained by Particle Dynamic Analyzer(PDA) measurement technology, and through fitting the data we get the 2-D probability distribution of the saltating particle’s lift-off velocity which considers both horizontal and vertical velocity. Then, some simulations of sand saltation on the basis of the 2-D probability distribution are conducted to predict the wind profile, the sand flux per unit area and unit time varying with height, and sand transport rate in the wind-blown sand flux at different free-stream wind velocities and different diameters of sand. Finally, the numerical results are compare to the former numerical results without taking account of the distribution of saltating particle’s horizontal velocity. The results show that the effect of the saltating particle’s horizontal lift-off velocity on those macroscopic quantities shouldn’t be ignored. The mid-air inter-particle collision generally is neglected in aeolian saltation .A theoretical simulation model is developed to calculate the probability of mid-air inter-particle collisions in an aeolian saltating cloud. The collision probabilities in the ascending, descending stages and the whole saltation process are calculated for the saltating particles with different lift-off velocity at different free-stream wind velocity based on the available data of particle concentration. The collision probabilities taking account of the distribution of saltating particle’s lift-off velocity are also calculated based on the available data of the probability distribution of the saltating particle’s lift-off velocity. The calculated probability reveals that the mid air inter-particle collision should not be neglected. It is an inevitable process when the free-stream wind velocity and the saltating particle’s lift-off velocity are high enough. " URL 查看原文 Language 中文 Document Type 学位论文 Identifier https://ir.lzu.edu.cn/handle/262010/230035 Collection 物理科学与技术学院 Recommended CitationGB/T 7714 张亚丽. 风沙流跃移沙粒运动的若干基本问题[D]. 兰州. 兰州大学,2005.
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