兰州大学机构库 >土木工程与力学学院
热扩散、热对流对风沙运动的影响研究
Alternative TitleStudy in Wind-Blown Sand Motion with Thermal Diffusion and Heat Convection
岳高伟
Thesis Advisor郑晓静 ; 黄宁
2008-01-27
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword地表温度 热扩散 热对流 风沙运动 沙粒起动 跃移运动 风沙流 风-沙-电耦合作用 尘卷
Abstract本文针对风沙运动中由于地表温度引起的近地层大气热扩散-热对流的动力学问题,结合风沙电这一自然现象,开展了有关地表温度作用下热对流和热扩散流场中的风沙运动机理微宏观方面的一些理论建模及分析研究。首先从理论上系统分析了床面沙粒在流场作用下的起动和跃移;进而定量分析了地表温度作用下风沙流中的输沙律、单宽输沙率及风沙电场随风沙流发展过程的变化等宏观物理量;最后通过理论模拟再现了大气边界层热对流对风沙运动的影响等。主要研究内容如下: 1、在考虑地表温度作用的基础上,建立热对流-热扩散方程,数值模拟了热扩散、热对流-热扩散、强热对流下的风场动力,是后面章节研究风沙运动的基础。 2、在水平风速和热扩散产生的垂向风速的作用下,数值计算了热扩散流场中沙粒的起动及其跃移轨迹;结果发现床面温度越高,沙粒的起动风速越小;而且使得沙粒跃移轨迹的最大高度和跨度都变大。 3、在风沙流中风沙电场是变化的。从而建立受热扩散影响下的风速(垂直和水平风速)、沙粒运动和电场相互耦合的风沙运动理论模型,数值计算了在风沙流发展过程中带电沙 粒产生的随时间变化的风沙电场、单宽输沙率及输沙率等物理量。 4、在考虑地表温度作用的近地层流场的基础上,通过建立近地层(50米以下)热对流及热扩散的气流运动方程等,采用大涡模拟的方法,数值模拟了近地层的流场及沙尘运动规律,为地表层沙尘向高空运动过渡建立了联系。 5、从局部地表高温对近地层大气运动的影响出发,数值模拟了强热对流引起尘卷风的演化过程及沙尘在尘卷风中的运动情况等,从理论上证明了热泡是引发尘卷的主要因素。并对尘卷中带电沙粒形成的电场进行了定量研究。
Other AbstractConcerning problems on atmosphere dynamics of thermal diffusion and thermal convection produced by the sand-bed temperature in the mechanism of wind-blown sand movement, this dissertation presents some theoretical modeling and analysis for wind-blown sand movement and the natural phenomenon of electrification with thermal diffusion and thermal convection. First threshold wind and saltating trajectory of sand are quantitatively calculated with influence of thermal diffusion; then wind-blown sand flux is simulated and some pivotal results are obtained; finally wind-blow sand motion effected by heat convection in atmospheric boundary layer is reappeared through theoretical simulation. The main achievements are made in the following aspects: 1、Based on considering the sand-bed temperature, the equations on thermal diffusion and thermal convection are founded and used to simulate wind dynamics. This is the base for studying wind-blown sand motion in following chapters. 2、The process is quantificationally analyzed that sand starts and saltates in space in wind field with the effluence of thermal diffusion produced by the sand-bed temperature. If the sand-bed temperature is higher, the sand threshold wind velocity is smaller and both of the maximal saltating height and span become bigger. 3、A theoretical model with thermal diffusion from the sand-bed is suggested to account for the effects of both thermal diffusion and electric field produced by charged sand grains during the evolution of wind-blown sand flux, where the coupled interaction is among wind velocity (vertical and horizontal wind), sand movement and the electric field. Then the evolution of wind-blown sand flux is simulated, and some pivotal results can be obtained, such as variational electric field、the transport rate of grains and so on. 4、Applying Large-Eddy-Simulaton method, the atmospheric boundary layer equations are calculated numerically with thermal diffusion and thermal convection, and sand and dust motion law is simulated in this wind field. 5、Dust devil is simulated with strong thermal convection coming of the earth's surface energy, its evolution process is qualitatively described and sand motion from the sand-bed to space is calculated. And it has proved that heat froth is the main factor which produces dust devil. At the same time the electric field in dust devil is quantificationally analyzed.
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226019
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
岳高伟. 热扩散、热对流对风沙运动的影响研究[D]. 兰州. 兰州大学,2008.
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