风沙流的实验研究和蠕移动的非线性动力分析
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摘要
本学位论文主要研究了风沙流的风洞实验和蠕移运动。首先探讨了湍流对输沙风沙流结构的影响,并通过改变湍流度的大小研究了湍流度对风沙流结构的影响。实验测量了两种湍流度下的风沙流结构,结果表明湍流度对输沙量的变化有一定影响,且会随着风速和高度的增大而增强。结果还表明地表湍流度的提高会使更多的沙粒离开床面而跃移到更高的位置,并认为湍流度的不同是造成戈壁与沙面上风沙流结构的不同的原因之一。
其次,利用PIV测量技术在风洞中测量床面起沙率。利用PIV技术的互相关算法计算出颗粒的速度,然后通过两幅图像的时间关系得出位移,从而得到沙面起动的沙粒个数。使用最小二乘法得出平坦沙面的起沙率与摩阻速度的相应公式。同时还分析了平坦沙面起动的颗粒粒径分布情况,结果表明粒径是按照正态分布的,随着摩阻速度的增大会使更多粒径大的颗粒起动。
最后,从沙粒受力出发,建立了床面层内蠕移集体运动的微分方程,进而从微分方程特性出发,探讨了蠕移运动过程的非线性动力学特征.发现沙粒的起动、蠕移运动的速度均受蠕移运动过程的非线性动力特征参数所控制,它们分别对应于蠕移运动过程中不同的非线性状态:而蠕移运动过程的非线性动力特征参数又取决于沙粒起动Shields参数和颗粒Reynold数,是两者的复杂函数.给出了沙粒的起动和蠕移沙粒的运动速度与shields参数和雷诺数的关系。
This dissertation first reports the effects of the turbulence intensity on the structures of wind-sand currents by simulating the boundaries in actual atmospheric turbulences. In the experimental simulation processes, two approaches, i.e., minaret and rough elements, were adopted, and the turbulence intensity served as a variable. The structures of the wind-sand currents were measured at two turbulence degrees, indicating that the turbulence degree significantly impacts the transport quantity of sand and this effect increases with the wind velocity and height. The increment of the turbulence on the earth's surface can make more sand particles leave the surface and jump to higher space. Also, we believe that one reason that causes the difference between the wind-sand currents on Gobi and sand surface is due to the different turbulence degrees in both cases, and the turbulence degree should be considered when designing sand-defence projects.
Then, the study of the dust emission perpendicular to the sand surface is meaningful for understanding the formation mechanisms of wind-sand currents and dust storms. In this paper, the dust emission rate was measured using the Particle Image Velocimetry technique in a wind tunnel. The velocity of sand grains was calculated the cross-correlation arithmetic based on the PTV technique, and then the displacement was obtained from the time relation from both, imagines. Based on the above calculation, the number of sand grains moving up from the sand surface could be achieved, and it was found that the dust emission rate varies linearly with the square of the friction speed from the analysis using the method of least squares and the corresponding formula was obtained. The analysis of the distribution of the grain size indicates that the grain size varies following the normal distribution. As the friction speed increased of the impact of the large particles will be larger.
Finally, the differential equation of collective creeping in stratum of the bed was founded based on the force analysis of sand particles. And from the characteristic of the equation, non-linear dynamic features of the differential equation were discussed. Found that the entraining and creeping velocity of the sand are controlled by the non-linear dynamic characteristic parameters of the equation and corresponding to the different non-linear states, respectively. The non-linear dynamic characteristic parameters of creeping depend on the entraining Shields parameters and Reynold number of sand. The non-linear dynamic characteristic parameters are complex function of Shields parameters and Reynold number, and the relationship between them was given.
其次,利用PIV测量技术在风洞中测量床面起沙率。利用PIV技术的互相关算法计算出颗粒的速度,然后通过两幅图像的时间关系得出位移,从而得到沙面起动的沙粒个数。使用最小二乘法得出平坦沙面的起沙率与摩阻速度的相应公式。同时还分析了平坦沙面起动的颗粒粒径分布情况,结果表明粒径是按照正态分布的,随着摩阻速度的增大会使更多粒径大的颗粒起动。
最后,从沙粒受力出发,建立了床面层内蠕移集体运动的微分方程,进而从微分方程特性出发,探讨了蠕移运动过程的非线性动力学特征.发现沙粒的起动、蠕移运动的速度均受蠕移运动过程的非线性动力特征参数所控制,它们分别对应于蠕移运动过程中不同的非线性状态:而蠕移运动过程的非线性动力特征参数又取决于沙粒起动Shields参数和颗粒Reynold数,是两者的复杂函数.给出了沙粒的起动和蠕移沙粒的运动速度与shields参数和雷诺数的关系。
This dissertation first reports the effects of the turbulence intensity on the structures of wind-sand currents by simulating the boundaries in actual atmospheric turbulences. In the experimental simulation processes, two approaches, i.e., minaret and rough elements, were adopted, and the turbulence intensity served as a variable. The structures of the wind-sand currents were measured at two turbulence degrees, indicating that the turbulence degree significantly impacts the transport quantity of sand and this effect increases with the wind velocity and height. The increment of the turbulence on the earth's surface can make more sand particles leave the surface and jump to higher space. Also, we believe that one reason that causes the difference between the wind-sand currents on Gobi and sand surface is due to the different turbulence degrees in both cases, and the turbulence degree should be considered when designing sand-defence projects.
Then, the study of the dust emission perpendicular to the sand surface is meaningful for understanding the formation mechanisms of wind-sand currents and dust storms. In this paper, the dust emission rate was measured using the Particle Image Velocimetry technique in a wind tunnel. The velocity of sand grains was calculated the cross-correlation arithmetic based on the PTV technique, and then the displacement was obtained from the time relation from both, imagines. Based on the above calculation, the number of sand grains moving up from the sand surface could be achieved, and it was found that the dust emission rate varies linearly with the square of the friction speed from the analysis using the method of least squares and the corresponding formula was obtained. The analysis of the distribution of the grain size indicates that the grain size varies following the normal distribution. As the friction speed increased of the impact of the large particles will be larger.
Finally, the differential equation of collective creeping in stratum of the bed was founded based on the force analysis of sand particles. And from the characteristic of the equation, non-linear dynamic features of the differential equation were discussed. Found that the entraining and creeping velocity of the sand are controlled by the non-linear dynamic characteristic parameters of the equation and corresponding to the different non-linear states, respectively. The non-linear dynamic characteristic parameters of creeping depend on the entraining Shields parameters and Reynold number of sand. The non-linear dynamic characteristic parameters are complex function of Shields parameters and Reynold number, and the relationship between them was given.
引文
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[28]L Xie,Y Q Ling,X J Zheng.Laboratory measurement of saltating sand particles' angular velocities and simulation of its effect on saltation trajectory.Journal of Geophysical Research,2007,112:D12116.
[29]郑晓静,薄天利,谢莉.风成纱波纹的离散粒子追踪法模拟.中国科学G辑,2007,37:527-534.
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[34]张亚丽.风沙流跃移沙粒运动的若干基本问题.兰州大学硕士论文,2005.
[35]任珊.空中碰撞和野外脉动风速对于风沙跃移运动的影响.兰州大学硕士论文,2007.
[36]庞加斌.沿海和山区强风特征的观测分析与风洞模拟研究.同济大学博士论文,2006.
[37]孙建华,赵琳娜,赵思雄.华北强沙尘暴的数值模拟及沙源分析.气候与环境研究,2004,9(1):139-154.
[38]宣捷.中国北方地面起尘总量分布.环境科学学报,2000,20(4):426-430.
[39]沈志宝,申彦波,杜明远.沙尘暴期间戈壁沙地起沙率的观测结果.高原气象,2003,12:545-550.
[40]Tegen Ina,Inez Fung.Modeling of mineral dust in the atmosphere:Sources,transport,and optical thickness.Journal of Geophysical Research,1994,99:22897-22914.
[41]Duce R A.Long-range atmospheric transport of soil dust from Asia to the tropical North Pacific temporal variability.Science,1980,209:1522-1524.
[42]王振亭.沙床表层颗粒的运动及生物固结.兰州大学博士论文,2005.
[43]Dong Z.,Qiang G.,Luo W.,et al..Characterizing the height profile of the flux of wind-eroded sediment.Environ Geol,2007,51:21-30.
[44]程旭.风沙两相流中沙粒起动规律的实验研究.清华大学硕士论文,2003.
[45]Shields A.Anwendurtg der ahnlichkeitsmechanik und der turbulenzforschung auf die Geschiebebewegung,Mitt Der Preussischen Versuchsanstalt for W asserbau und Schiffbau,No.26,Berlin,1936.
[46]黄鹏.大气边界层模拟及测试技术.同济大学学报,2001,29(1):40-44.
[47]张克存,屈建军.戈壁风沙流结构和风速廓线的特征研究.水土保持研究,2005,2:54-58.
[48]张正偲,董治宝,赵爱国.沙漠地区风沙活动特征.干旱区研究,2007,4:550-554.
[49]宣捷.低层大气中固体粒子运动物理运动及其模拟.环境科学学报,1998,18(3):350.
[50]张伟,葛耀君,杨永昕.粒子图像测速技术相关算法研究进展.力学与进展,2007,3:443-452.
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[3]国家林业局.中国荒漠化和沙化状况公告.中国绿色时报,2005-06-15.
[4]Anderson R.S.,Haff P.K.Wind modification and bed response during saltation of sand in air.Acta.Mech.,1991,1:21-25.
[5]Shao Y.Physics and modeling of wind erosion.Boston:Kluwer Academic Publishers,2000.
[6]Bagnold R.A.The physics of blown sand and desert dune.London:Methuen,1941.
[7]Goudie A.S.Dust storms and their geomorphological implication.J.Arid Environments,1978,1:291-311.
[8]董飞,刘大有,贺大良.风沙运动的研究进展和发展趋势.力学进展,1995,25:368-391.
[9]王涛,陈广庭.中国北方沙尘暴现状及对策.中国沙漠,2001,21:322-327.
[10]邢茂,郭烈锦.紊流风场中起跳沙粒的轨迹特征.中国沙漠,2003,23(6):637-641.
[11]邢茂,郭烈锦.风沙稳定输运中起跳沙粒运动状态分布函数.工程热物理学报,2004,25(4):484-550.
[12]杨保,邹学勇.风沙流中颗粒跃移研究的某些进展与问题.中国沙漠,1999,19:173-178.
[13]B.R.White.Two-phase movement of saltatmg turbulent boundary layer flow.Int.I.Multiphase Flow,1982,8:459-473.
[14]刘贤万.实验风沙物理与风沙工程学.北京:科学出版社,1995.
[15]岳高伟,黄宁,郑晓静.沙粒形状不规则及静电力对起动风速的影响.中国沙漠,2003,23(6):621-627.
[16]郑晓静,谢莉.沙粒起跳自旋的分析.中国沙漠,2003,23(6):632-636.
[17]邹学勇,董光荣.风沙物理学的发展与展望.地球科学进展,1993,8:44-49.
[18]Anderson R.S.,Haff P.K.Simulation of aeolian saltation.Science,1988,241:820-823.
[19]McEwan I.K.,Willetts B.B.,Rice M.A.The grain/bed collision in sand transport by wrack Sedimentology,1992,39:971-981.
[20]Nalpanis P.Saltating and suspended particles over flat and sloping surfaces Ⅱ.Experiments and numerical simulations.In:Proceedings of International Workshop on the Physics of Blown Sand.1,Memoir 8,University of Aarhus,Denmark,1985.
[21]Nalpanis P.,Hunt J.C.R.,Barrett C.F.Saltating particles over flat beds.J.Fluid Mech.,1993,251:661-685.
[22]Rice M.A.,Willetts B.B.,McEwan I.K.Observations of collisions of saltating grains with a granular bed from high-speed cine-film.Sedimentology,1996,43:21-31.
[23]Zingg A W.Wind tunnel studies of the movement of sedimentary materials.In:Proceedings 5th Hydraulic Conference,Bull,Univ.of Lowa city,1953:111-135.
[24]黄宁.沙粒带电及风沙电场对风沙跃移运动影响的研究.兰州大学博士论文,2002.
[25]Anderson R.S.,Sorensen M.,Willetts B.B.A review of recent progress in our understanding of Aeolian sediment transport.Acta.Mech.,1991,1:1-19.
[26]X J Zheng.Mechanics of Wind-blown Sand Movement.German:Spring,2009.
[27]X Y Zheng,L Xie,X Y Zou.Theoretical prediction of liftoff angular velocity distributions of sand particles in wind-blown sand flux.Journal of Geophysical Research,2006,111:D11109.
[28]L Xie,Y Q Ling,X J Zheng.Laboratory measurement of saltating sand particles' angular velocities and simulation of its effect on saltation trajectory.Journal of Geophysical Research,2007,112:D12116.
[29]郑晓静,薄天利,谢莉.风成纱波纹的离散粒子追踪法模拟.中国科学G辑,2007,37:527-534.
[30]X Y Zheng,T L Bo,W Zhu.A scale-coupled method for simulation of the formation and evolution of aeolian dune field.International Journal of Nonlinear Science and Numerical Simulation,2007,10(3):387-395.
[31]Kawamura R.Study on sand movement by wind.Report Institute Sci.& Tech.Univ.Tokeyo,1951,5:95-112.
[32]Owen P.R.Saltation of uniform grains in air.J.Fluid Mech.,1964,20:225-242.
[33]Zhou Y.H.,Guo X.,Zheng X.J.Experimental measurement of wind-sand flux and sand transport for naturally mixed sands.Physical Review E,2002,66:021305.
[34]张亚丽.风沙流跃移沙粒运动的若干基本问题.兰州大学硕士论文,2005.
[35]任珊.空中碰撞和野外脉动风速对于风沙跃移运动的影响.兰州大学硕士论文,2007.
[36]庞加斌.沿海和山区强风特征的观测分析与风洞模拟研究.同济大学博士论文,2006.
[37]孙建华,赵琳娜,赵思雄.华北强沙尘暴的数值模拟及沙源分析.气候与环境研究,2004,9(1):139-154.
[38]宣捷.中国北方地面起尘总量分布.环境科学学报,2000,20(4):426-430.
[39]沈志宝,申彦波,杜明远.沙尘暴期间戈壁沙地起沙率的观测结果.高原气象,2003,12:545-550.
[40]Tegen Ina,Inez Fung.Modeling of mineral dust in the atmosphere:Sources,transport,and optical thickness.Journal of Geophysical Research,1994,99:22897-22914.
[41]Duce R A.Long-range atmospheric transport of soil dust from Asia to the tropical North Pacific temporal variability.Science,1980,209:1522-1524.
[42]王振亭.沙床表层颗粒的运动及生物固结.兰州大学博士论文,2005.
[43]Dong Z.,Qiang G.,Luo W.,et al..Characterizing the height profile of the flux of wind-eroded sediment.Environ Geol,2007,51:21-30.
[44]程旭.风沙两相流中沙粒起动规律的实验研究.清华大学硕士论文,2003.
[45]Shields A.Anwendurtg der ahnlichkeitsmechanik und der turbulenzforschung auf die Geschiebebewegung,Mitt Der Preussischen Versuchsanstalt for W asserbau und Schiffbau,No.26,Berlin,1936.
[46]黄鹏.大气边界层模拟及测试技术.同济大学学报,2001,29(1):40-44.
[47]张克存,屈建军.戈壁风沙流结构和风速廓线的特征研究.水土保持研究,2005,2:54-58.
[48]张正偲,董治宝,赵爱国.沙漠地区风沙活动特征.干旱区研究,2007,4:550-554.
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