兰州大学机构库 >土木工程与力学学院
风沙流中沙粒流体起动判定条件的研究
Alternative TitleThe research on the criteria of incipient motion of sand particles in windblown sand
李政
Thesis Advisor薄天利
2014-05-28
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword风沙流 沙粒起动 冲量 输沙率 响应时间
Abstract风沙流的演化过程一直以来都是众多学者所关心的问题,仅通过实验往往很难给出风沙流演化过程的一些定量结果,常要结合数值模拟和理论分析来对风沙流的演化过程进行预测。在风沙流演化过程的预测中,地表沙粒起动的判定是影响预测结果的一个重要因素。已有沙粒流体起动一般是通过平均风速或瞬时风速与临界起动风速进行对比来判断是否满足流体起动条件的。本文结合已有的工作提出了一种根据冲量来预测床面沙粒流体起动的新方法,该方法主要是通过判断风速大于临界风速时间段内流场作用的总冲量是否大于沙粒启动的临界冲量来进行判定的。如果总冲量大于临界冲量则床面沙粒起动,反之,则沙粒不能起动。同时,从理论上对比了该方法与已有方法对沙粒流体起动判定结果的影响。最后,本文把该判定方法应用到风沙流数值模拟程序中,对输沙率进行估算,并将计算结果与已有的方法算得的输沙率结果进行比较,得出了与理论分析一致的结果。同时给出了采用不同方法对输沙率计算结果定量的比较,并通过结果的对比讨论了输沙率对风速的响应时间滞后的问题,为这一问题的深入研究提供了一个新的思路。
Other AbstractThe evolution process of windblown sand has always been of concern to many scholars. Due to the particularity of windblown sand, the observations in experimental study are often affected by the experimental equipment and the surrounding environment, thus limiting the awareness of windblown sand. So it is difficult to get some quantitative results in predicting the evolution process of windblown sand only through experiment. The numerical simulation and theoretical analysis are often combined with experiment to predict the evolution process. The incipient motion of sand particle from sand bed plays a very important role in the prediction of evolution process of windblown sand. The comparison between average or instantaneous wind speed and critical wind speed is usually used to determine whether the criteria of incipient motion of sand particle can be satisfied. Based on existing work, this paper proposes a new method for the prediction of incipient motion of sand particle based on wind speed fluctuation, i.e., in duration when the wind speed is larger than the critical wind speed, if the total impulse on sand particle is larger than the critical impulse, incipient motion of sand particle occurs, or incipient motion of sand particle cannot occur. This paper also theoretically compares the effect of the new method with existing methods in judging the incipient motion of sand particle. Moreover, from the analysis of entrainment in the rolling and lifting modes, we find that when the average wind speed is smaller than the critical wind speed, average wind speed is used to judge the incipient motion of sand particle, it will underestimate the number of sand particles jumping from the bed, and instantaneous wind speed is used to judge incipient motion of sand particle, it will overestimate the number of sand particles jumping from the bed; when the average wind speed is larger than the critical wind speed, average wind speed and instantaneous wind speed were used to judge the incipient motion of sand particle, it will overestimate the number of sand particles jumping from the bed. Finally, this paper applies this method to the simulation program of windblown sand for the estimation of sand transport rate. Through the comparison between the results of sand transport rate calculated by this new method and the previous methods, it is concluded that the results are consistent with theoretical analysis. Meanwhile, this paper shows the comparison among the results ...
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226513
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
李政. 风沙流中沙粒流体起动判定条件的研究[D]. 兰州. 兰州大学,2014.
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