沙粒跃移轨迹的数值模拟研究
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摘要
单颗沙粒的运动规律是联系风沙流宏观研究和微观研究的纽带。在沙粒运动的三种基本方式(跃移,悬移和蠕移)中,以跃移运动最为重要。本文比较了常用的描述气固两相流流动的数学模型,选用能够真实描述沙粒运动特征的离散相模型(Discrete Particle Model)进行沙粒跃移轨迹的数值模拟。
从来流的风场结构出发,分析了不同的风场结构对沙粒连续跃移轨迹的影响,得出在对数风速廓线和周期性正弦条件下沙粒连续跃移的次数要比实测沙漠环境阵风条件下少一次,说明来流的波动对沙粒跃移的轨迹有显著影响。在此基础上,讨论了湍流强度和平均风速对沙粒跃移轨迹的影响,得出当湍流强度和平均风速一定时,粒径小于等于临界粒径时沙粒的跃移轨迹不是光滑的抛物线;粒径大于临界粒径时沙粒的跃移轨迹明显为光滑的抛物线,因而数值计算时只需要考虑小于等于临界粒径的湍流影响;当来流湍流强度一定时,临界粒径随着平均风速的增大而增大;当平均风速一定,临界粒径在200μm以下时,随着湍流强度的增大临界粒径增大,当临界粒径在200μm以上时,随着湍流强度的增大临界粒径不再变化。
采用HL模型和沙粒的球形系数修正方法,进行了沙粒形状因素对跃移轨迹的影响的数值计算,并与沙粒跃移轨迹高速摄影实验做了比较,结果表明,不考虑沙粒形状因素得到的轨迹与实验轨迹偏差很大,HL模型模拟的轨迹与实验轨迹的偏差主要表现在水平方向上,垂直方向上一致性良好;利用沙粒球形系数修正法得到的模拟轨迹与实验轨迹在粒径为200～300μm时,沙粒跃移高度和跃移距离与实验数据的误差分别为0.2%和3.5%;当粒径为100～125μm时,为12.4%和0.16%。
The single sand law of motion is relates the wind-blown sand macroexamination and the microexamination link.Saltation is the most significant in the three basic forms (Saltation,Suspension and Creep) of sand movement blown by wind.In this paper,by comparing the common models in the numerical simulation of gas-solid flow, Lagrangian discrete particle model was chosen to achieve the real characteristics of the sand saltation.
Sand saltation trajectories were calculated under the different inflow conditions such as logarithmic distribution,periodic sinusoidal and field gust of wind speed.The results showed that the consecutive saltation times of each saltation trajectories under former two wind conditions was less than that under gust condition.Next the influence of the turbulent intensity and the averaged wind speed on the saltation trajectories were discussed.It could be found that when the turbulent intensity and the averaged wind speed remained were fixed,the saltation trajectories of the sand with size less than the critical diameter were not smooth parabola unlike the trajectories of the sand with the size larger than the critical diameter.Therefore the influence of the turbulence on sand saltation needs to be considered in the numerical simulation when the sand size was less than critical diameter.When the turbulent intensity remained was definite value, the critical diameter of sand saltation sand increased with the averaged wind speed increased;when the averaged wind speed was fixed,the critical diameter increased with the turbulent intensity increased until the critical diameter grew up 200μm.
The HL-model and the shape factor modification of sand were used in the numerical simulations of the sand saltation to study the effect of the sand's irregular shape on sand motion,and the simulation results were compared with measurement data of the high speed camera experiment.The results showed that the deviations were significant when the shape factor were not considered in the numerical simulations. The simulation results using HL-model were coincident with the experimental data in the vertical direction,and deviated obviously in the horizontal direction.For 200～300μm sand particles,the deviations of saltation height and saltation distance between the results of simulation using shape factor modification and experiment were 0.2%and 3.5%,and for 100～125μm sand particles,the deviations were 0.16%and 12.4%.
从来流的风场结构出发,分析了不同的风场结构对沙粒连续跃移轨迹的影响,得出在对数风速廓线和周期性正弦条件下沙粒连续跃移的次数要比实测沙漠环境阵风条件下少一次,说明来流的波动对沙粒跃移的轨迹有显著影响。在此基础上,讨论了湍流强度和平均风速对沙粒跃移轨迹的影响,得出当湍流强度和平均风速一定时,粒径小于等于临界粒径时沙粒的跃移轨迹不是光滑的抛物线;粒径大于临界粒径时沙粒的跃移轨迹明显为光滑的抛物线,因而数值计算时只需要考虑小于等于临界粒径的湍流影响;当来流湍流强度一定时,临界粒径随着平均风速的增大而增大;当平均风速一定,临界粒径在200μm以下时,随着湍流强度的增大临界粒径增大,当临界粒径在200μm以上时,随着湍流强度的增大临界粒径不再变化。
采用HL模型和沙粒的球形系数修正方法,进行了沙粒形状因素对跃移轨迹的影响的数值计算,并与沙粒跃移轨迹高速摄影实验做了比较,结果表明,不考虑沙粒形状因素得到的轨迹与实验轨迹偏差很大,HL模型模拟的轨迹与实验轨迹的偏差主要表现在水平方向上,垂直方向上一致性良好;利用沙粒球形系数修正法得到的模拟轨迹与实验轨迹在粒径为200～300μm时,沙粒跃移高度和跃移距离与实验数据的误差分别为0.2%和3.5%;当粒径为100～125μm时,为12.4%和0.16%。
The single sand law of motion is relates the wind-blown sand macroexamination and the microexamination link.Saltation is the most significant in the three basic forms (Saltation,Suspension and Creep) of sand movement blown by wind.In this paper,by comparing the common models in the numerical simulation of gas-solid flow, Lagrangian discrete particle model was chosen to achieve the real characteristics of the sand saltation.
Sand saltation trajectories were calculated under the different inflow conditions such as logarithmic distribution,periodic sinusoidal and field gust of wind speed.The results showed that the consecutive saltation times of each saltation trajectories under former two wind conditions was less than that under gust condition.Next the influence of the turbulent intensity and the averaged wind speed on the saltation trajectories were discussed.It could be found that when the turbulent intensity and the averaged wind speed remained were fixed,the saltation trajectories of the sand with size less than the critical diameter were not smooth parabola unlike the trajectories of the sand with the size larger than the critical diameter.Therefore the influence of the turbulence on sand saltation needs to be considered in the numerical simulation when the sand size was less than critical diameter.When the turbulent intensity remained was definite value, the critical diameter of sand saltation sand increased with the averaged wind speed increased;when the averaged wind speed was fixed,the critical diameter increased with the turbulent intensity increased until the critical diameter grew up 200μm.
The HL-model and the shape factor modification of sand were used in the numerical simulations of the sand saltation to study the effect of the sand's irregular shape on sand motion,and the simulation results were compared with measurement data of the high speed camera experiment.The results showed that the deviations were significant when the shape factor were not considered in the numerical simulations. The simulation results using HL-model were coincident with the experimental data in the vertical direction,and deviated obviously in the horizontal direction.For 200～300μm sand particles,the deviations of saltation height and saltation distance between the results of simulation using shape factor modification and experiment were 0.2%and 3.5%,and for 100～125μm sand particles,the deviations were 0.16%and 12.4%.
引文
[1]朱振达.中国的沙漠化及其治理[M].北京:北京科学出版社,1989,60
[2]夏讯成,杨根生.黑风暴[M].北京:科学出版社,1995
[3]郑晓静,周又和.风沙运动中的若干关键力学问题[J].力学与实践,2003,4,25-2
[4]朱朝云.风沙物理学[M].北京:中国林业出版社,1991
[5]Bagnold R A(钱宁,林秉南译).风沙和荒漠沙丘物理学[M].北京:科学出版社,1959
[6]凌裕泉,吴正.风沙运动得动态摄影实验[J].中国沙漠,1988,8(1):18-27
[7]刘大有,董飞,贺大良.风沙两相流运动特点分析[J].地理学报,1996,5:434-444
[8]贺大良,刘大有.跃移沙粒起跳的受力机制[J].中国沙漠,1989年第9卷 第2期
[9]戚隆溪,王柏懿.土壤侵蚀的流体力学[J].力学进展,1996,2:14-22
[10]邹学勇,郝青振,张春来等.风沙流中跃移沙粒轨迹参数分析[J].科学通报,1999,10:134-145
[11]陈东,曹文洪,傅铃燕等.风沙运动的初步研究[J].泥沙研究,1999,6:84-89
[12]倪晋仁,李振山.风沙两相流理论及其应用[J].科学出版社,2000
[13]吉艳丽.沙粒跃移轨迹的数值模拟与试验研究[D].西安建筑科技大学硕士学位论文,2006
[14]Anderson R S,Hallet B.Sediment transport by wind:Toward a general model.Geol SocAm Bull[J].1986,97:523-525
[15]White B R,Schulz J C,Magnus effect in saltation[J].Fluid Mech,1997,81(3):497-511
[16]黄宁,郑晓静.风沙跃移运动中的Magnus效应[J].兰州大学学报(自认科学版),2001,6,37-3
[17]杨保,邹学勇,王周龙等.流中跃移颗粒的受力分析[J].地理科学,1999年第19卷第5期
[18]武建军,阎光虎.风沙电多场耦合中沙粒运动的受力分析[J].科学G辑:物理学、力学、天文学,2008,38-8:973-983
[19]Anderson R S.Simulation of Eolian Sa!tation[J].Science,1988,241:820-823
[20]Tsuji Y,Kawaguchi Tanaka T.Discrete particle simulation of two dimensional fluidized beds[J].Chemical Engineering Science,1993 77(1):79-87
[21]Owen PR.Saltation of uniform grins in air[J].J of Fluid Mech,1964,20:225-242
[22]Ungar J,Haft PK.Steady state saltation in air[J].Sedimentology,1987,34:289-299
[23]刘贤万.颗粒运动及其数理简析[J].中国沙漠,1999年第13卷第二期
[24]刘绍中,杨绍华,凌裕泉.沙粒跃移模型及其数值分析[J].计算物理,2(4):444-453
[25]孙其诚,王光谦.模拟风沙运动的离散颗粒动力学模型[J].泥沙研究,2001,4:12-18
[26]董飞,刘大有,贺大良.风沙运动的研究进展和发展趋势[J].力学进展,1995,25(3):368-391
[27]吴正.风沙地貌与治沙工程学[M].北京:科学出版社2003
[28]王福军.计算流体动力学分析-CFD软件原理于应用[M].北京:清华大学出版社,2004
[29]王为术,徐维晖,翟肇江等.PISO算法的实现及与SIMPLE,SIMPLER,SIMPLEC算法收敛性的比较[J].华北水利水电学院学报,2007,28(4):33-36
[30]H.K.Versteeg,W.Malalasekera.An Introduction to Computational Fluid Dynamics.The Finite Volume Method[M].Wiley,New York,1995
[31]Bagnold RA.The Physics of Blown Sand and Desert Dunes[J].Methuen L ondon,1941
[32]李万清.跃移运动的粒.床随即碰撞数值模拟研究[D].兰州大学博士学位论文,2007
[33]Willetts M A,aine S E.Shape effectsin aeolian graintransport,Sedimentology[J].29:409-417
[34]Williamms G.Some aspects of the eolian saltation load[J].Sedimentology,1964,3:257-287
[35]李振山,倪晋仁,王光谦.风洞边壁对携沙气流流速分布的影响[J].泥沙研究,2001,5:27-32
[2]夏讯成,杨根生.黑风暴[M].北京:科学出版社,1995
[3]郑晓静,周又和.风沙运动中的若干关键力学问题[J].力学与实践,2003,4,25-2
[4]朱朝云.风沙物理学[M].北京:中国林业出版社,1991
[5]Bagnold R A(钱宁,林秉南译).风沙和荒漠沙丘物理学[M].北京:科学出版社,1959
[6]凌裕泉,吴正.风沙运动得动态摄影实验[J].中国沙漠,1988,8(1):18-27
[7]刘大有,董飞,贺大良.风沙两相流运动特点分析[J].地理学报,1996,5:434-444
[8]贺大良,刘大有.跃移沙粒起跳的受力机制[J].中国沙漠,1989年第9卷 第2期
[9]戚隆溪,王柏懿.土壤侵蚀的流体力学[J].力学进展,1996,2:14-22
[10]邹学勇,郝青振,张春来等.风沙流中跃移沙粒轨迹参数分析[J].科学通报,1999,10:134-145
[11]陈东,曹文洪,傅铃燕等.风沙运动的初步研究[J].泥沙研究,1999,6:84-89
[12]倪晋仁,李振山.风沙两相流理论及其应用[J].科学出版社,2000
[13]吉艳丽.沙粒跃移轨迹的数值模拟与试验研究[D].西安建筑科技大学硕士学位论文,2006
[14]Anderson R S,Hallet B.Sediment transport by wind:Toward a general model.Geol SocAm Bull[J].1986,97:523-525
[15]White B R,Schulz J C,Magnus effect in saltation[J].Fluid Mech,1997,81(3):497-511
[16]黄宁,郑晓静.风沙跃移运动中的Magnus效应[J].兰州大学学报(自认科学版),2001,6,37-3
[17]杨保,邹学勇,王周龙等.流中跃移颗粒的受力分析[J].地理科学,1999年第19卷第5期
[18]武建军,阎光虎.风沙电多场耦合中沙粒运动的受力分析[J].科学G辑:物理学、力学、天文学,2008,38-8:973-983
[19]Anderson R S.Simulation of Eolian Sa!tation[J].Science,1988,241:820-823
[20]Tsuji Y,Kawaguchi Tanaka T.Discrete particle simulation of two dimensional fluidized beds[J].Chemical Engineering Science,1993 77(1):79-87
[21]Owen PR.Saltation of uniform grins in air[J].J of Fluid Mech,1964,20:225-242
[22]Ungar J,Haft PK.Steady state saltation in air[J].Sedimentology,1987,34:289-299
[23]刘贤万.颗粒运动及其数理简析[J].中国沙漠,1999年第13卷第二期
[24]刘绍中,杨绍华,凌裕泉.沙粒跃移模型及其数值分析[J].计算物理,2(4):444-453
[25]孙其诚,王光谦.模拟风沙运动的离散颗粒动力学模型[J].泥沙研究,2001,4:12-18
[26]董飞,刘大有,贺大良.风沙运动的研究进展和发展趋势[J].力学进展,1995,25(3):368-391
[27]吴正.风沙地貌与治沙工程学[M].北京:科学出版社2003
[28]王福军.计算流体动力学分析-CFD软件原理于应用[M].北京:清华大学出版社,2004
[29]王为术,徐维晖,翟肇江等.PISO算法的实现及与SIMPLE,SIMPLER,SIMPLEC算法收敛性的比较[J].华北水利水电学院学报,2007,28(4):33-36
[30]H.K.Versteeg,W.Malalasekera.An Introduction to Computational Fluid Dynamics.The Finite Volume Method[M].Wiley,New York,1995
[31]Bagnold RA.The Physics of Blown Sand and Desert Dunes[J].Methuen L ondon,1941
[32]李万清.跃移运动的粒.床随即碰撞数值模拟研究[D].兰州大学博士学位论文,2007
[33]Willetts M A,aine S E.Shape effectsin aeolian graintransport,Sedimentology[J].29:409-417
[34]Williamms G.Some aspects of the eolian saltation load[J].Sedimentology,1964,3:257-287
[35]李振山,倪晋仁,王光谦.风洞边壁对携沙气流流速分布的影响[J].泥沙研究,2001,5:27-32