| 沙粒起跳初速度分布函数的数值反演 |
| Alternative Title | The numerical inversion of initial lift-off speed distribution function of sand particals
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| 郑剑锋 |
| Thesis Advisor | 郑晓静
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| 2005-05-20
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| Degree Grantor | 兰州大学
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| Place of Conferral | 兰州
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| Degree Name | 硕士
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| Keyword | 多维约束最优化方法
风沙跃移运动
初速度分布函数
数值反演
输沙率
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| Abstract | 沙粒起跳的初速度分布函数是联系风沙跃移运动宏观研究和细观研究的重要途径之一。本文从风沙跃移运动的基本方程和数值模拟步骤出发，在风洞实验所得的不同风速下的输沙率及风速廓线的基础上，采用多维约束最优化方法，建立了沙粒起跳初速度分布函数的数值反演模式，在此基础上给出了不同风速下沙粒起跳初速度分布函数的数值结果，指出随着来流风速的增大，起跳速度大的沙粒的起跳概率不断增大，而起跳速度小的沙粒却与之相反。通过与实验结果的比较，证实了此种方法的可行性。
在已知初速度分布函数的基础上，利用稳态风沙流模型，通过输沙率和风速廓线计算值与实验值的比较，结果表明两者无论在定性还是定量上均吻合的较好，由此也验证了本文初速度分布函数的可靠性。
最后，考虑了非均匀沙沙粒粒径级配对风沙运动的影响，通过对沙粒粒径的分析，给出了非均匀沙沙粒粒径的分布函数。定量计算了不同风速下非均匀沙沙粒起跳初速度分布，并确定了分布函数；与均匀沙计算结果相比，在定性上一致，定量上存在差别，说明了研究非均匀沙时考虑沙粒级配的必要性；沙粒带电量对沙粒起跳初速度分布函数的影响的研究结果表明，沙粒带电也是影响初速度分布函数的一个重要因素。 |
| Other Abstract | The initial lift-off speed distribution function of sand particles plays an important role in linking macroscopic research and microcosmic research of wind-blown sand saltation. In this paper, by using the basic functions and the numerical simulating steps of saltating movement of wind-blown sand, and based on experimental results of sand fluxes and wind profiles in wind tunnel and the method of optimization with multi-constraints, an inverse model of the lift-off speed distribution of sand particles is established. The calculated numerical results under varied wind speeds indicate that the probability of high lift-off speed particles is greater than that of low lift-off speed particles with the increment of the wind speed. By comparing calculated numerical results to the results of experiments, this method is proved to be feasible.
After considering the coupling of wind 、electric field and sand, a numerical model for steady state wind-blown sand saltation is used on the basis of the obtained lift-off speed distribution of sand particles, and the numerical results of sand fluxes and wind profiles are fairly coincident with the experimental results qualitatively and quantitatively. It strengthens the reliability of the distributed function obtained in this paper.
Finally, a function of sand grain size distribution is obtained with concerning the influence to the wind-blown sand movement caused by the non-uniform sand-grading distribution. The initial lift-off speed distributions of non-uniform sand particles are calculated and then analyzed quantitatively at different axial wind velocities. After that, the initial lift-off speed distribution function of non-uniform sand is determined. The results are qualitatively in agreement with the uniform ones, and quantitatively in disagreement with the uniform ones. So it is necessary to consider sand-grading in research of wind-blown sand saltating movement; the results also show that the quantity of electricity with sands plays an import role in lift-off speed distribution of sands. |
| URL | 查看原文
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| Language | 中文
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| Document Type | 学位论文
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| Identifier | https://ir.lzu.edu.cn/handle/262010/229408
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| Collection | 物理科学与技术学院
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Recommended Citation
GB/T 7714 |
郑剑锋. 沙粒起跳初速度分布函数的数值反演[D]. 兰州. 兰州大学,2005.
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