稳态风场下的沙粒运动规律
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摘要
风沙运动是风沙地貌以及土壤侵蚀的主要原因,跃移运动是风沙运动的主要形式,跃移沙粒占整个运动沙粒的75%左右,这一运动不仅是沙量传输的主要运动形式,也是造成沙质地表风蚀和风沙灾害的根本原因.通过数值模拟的方式研究了当风沙运动达到稳定状态时的风沙流运动特征,详细讨论了稳态情况下沙粒的跃移运动规律,以期对防沙治沙工作能起到一定的指引.研究结果表明:在不同的初始风速条件下,当风沙运动达到稳定状态时在高度小于10倍的沙粒直径处的风速基本相同,这是由于地表风场被运动沙粒强烈修正,有效粗糙度随着摩阻风速的增加而增加;同时在给定的风场风速下,跃移轨迹和碰撞速度并不是无限增大的,而是存在最大的跃移轨迹和最大的碰撞速度,并且最大碰撞速度以及最大跃移轨迹的高度和长度与摩阻速度成线性关系.
Windblown sand movement is responsible for aeolian landforms,deflation and soil erosion. The saltation movement is the main form of windblown sand movement,it accounted for about 75%,which is not only a major sport in windblown sand movement,but also the reason of erosion. The windblown sand movement in steady and it's characteristic were discussed in detail,in order to be play on anti-desertification. The results showed that the wind speed in the reptating layer varies little at the different frication velocities,the wind in the steady state is modified by the sand grains in the air,and the effective roughness increases with the increase of friction velocity; Simultaneously,saltation trajectory and impact velocity is bounded,the maximum saltation trajectory and the maximum impact velocity present in a given wind speed; And the maximum impact speed and the maximum saltation height and length of tracks has a linear relationship with the friction.
Windblown sand movement is responsible for aeolian landforms,deflation and soil erosion. The saltation movement is the main form of windblown sand movement,it accounted for about 75%,which is not only a major sport in windblown sand movement,but also the reason of erosion. The windblown sand movement in steady and it's characteristic were discussed in detail,in order to be play on anti-desertification. The results showed that the wind speed in the reptating layer varies little at the different frication velocities,the wind in the steady state is modified by the sand grains in the air,and the effective roughness increases with the increase of friction velocity; Simultaneously,saltation trajectory and impact velocity is bounded,the maximum saltation trajectory and the maximum impact velocity present in a given wind speed; And the maximum impact speed and the maximum saltation height and length of tracks has a linear relationship with the friction.
引文
[1]郑晓静,周又和.风沙运动中的若干力学问题[J].力学与实践,2003,25(2):1-6.
[2]Bagnold R A.The physics of blown sand and desert dunes[M].New York:Willian Morrow,1941.
[3]吴正.风沙地貌与治沙工程学[M].北京:科学出版社,2003.
[4]Owen P R.Saltation of uniform grains in air[J].Journal of Fluid Mechanics,1964,20(2):225-242.
[5]Anderson R S,Haff P K.Simulation of eolian saltation[J].Science,1988,241:820-823.
[6]Anderson R S.Eolian sediment transport as a stochastic process:the effects of a fluctuating wind on particle trajectories[J].Journal of Geology,1987,95:497-512.
[7]Shao Y P.A similarity theory for saltation and application to aeolian mass flux[J].Boundary-Layer Meteorol,2005,115:319-338.
[8]Dong Z,Huang N,Liu X.Simulation of the probability of midair interparticle collisions in an aeolian saltating cloud[J].Journal of Geophysical Research,2005,110:D24113.
[9]Huang N,Zhang Y,Adamo R D.A model of the trajectories and midair collision probabilities of sand particles in a steady state saltation cloud[J].Journal of Geophysical Research,2007,112:D08206.
[10]Zheng X J,Huang N,Zhou Y H.Laboratory measurement of electrification of windblown sands and simulation of its effect on sand saltation movement[J].Journal of Geophysical Research,2003,108:4322.
[11]Kok J F,Renno N O.A comprehensive numerical model of steady state saltation(COMSALT)[J].Journal of Geophysical Research,2009,114:D17204.
[12]Anderson R S,Sorensen M,Willetts B B.A review of recent progress in our understanding of Aeolian sediment transport[J].Acta Mechanica,1991,1(Supl):1-19.
[13]Andreotti B.A two-species model of aeolian sand transport[J].Journal of Fluid Mechanics,2004,510,47-50.
[14]McEwan J K,Willetts B B,Rice M A.The grain/bed collision in sand transport by wind[J].Sedimentology,1992,39:971-981.
[15]Rioual F,Valance A,Bideau D.Experimental study of the collision process of a grain on a two-dimensional granular bed[J].Physical Review E,2000,62:2450-2459.
[16]Werner B T,Haff P K.The impact process in eolian saltation:two dimensional simulations[J].Sedimentology,1988,35:189-196.
[17]Iversen J D,Rasmussen K R.The effect of wind speed and bed slope on sand transport[J].Sedimentology,1999,46(4):723-731.
[18]Zhou Y H,Guo X,Zheng X J.Experimental measurement of wind-sand flux and sand transport for naturally mixed sands[J].Physical Review E.2002,66:021305.
[2]Bagnold R A.The physics of blown sand and desert dunes[M].New York:Willian Morrow,1941.
[3]吴正.风沙地貌与治沙工程学[M].北京:科学出版社,2003.
[4]Owen P R.Saltation of uniform grains in air[J].Journal of Fluid Mechanics,1964,20(2):225-242.
[5]Anderson R S,Haff P K.Simulation of eolian saltation[J].Science,1988,241:820-823.
[6]Anderson R S.Eolian sediment transport as a stochastic process:the effects of a fluctuating wind on particle trajectories[J].Journal of Geology,1987,95:497-512.
[7]Shao Y P.A similarity theory for saltation and application to aeolian mass flux[J].Boundary-Layer Meteorol,2005,115:319-338.
[8]Dong Z,Huang N,Liu X.Simulation of the probability of midair interparticle collisions in an aeolian saltating cloud[J].Journal of Geophysical Research,2005,110:D24113.
[9]Huang N,Zhang Y,Adamo R D.A model of the trajectories and midair collision probabilities of sand particles in a steady state saltation cloud[J].Journal of Geophysical Research,2007,112:D08206.
[10]Zheng X J,Huang N,Zhou Y H.Laboratory measurement of electrification of windblown sands and simulation of its effect on sand saltation movement[J].Journal of Geophysical Research,2003,108:4322.
[11]Kok J F,Renno N O.A comprehensive numerical model of steady state saltation(COMSALT)[J].Journal of Geophysical Research,2009,114:D17204.
[12]Anderson R S,Sorensen M,Willetts B B.A review of recent progress in our understanding of Aeolian sediment transport[J].Acta Mechanica,1991,1(Supl):1-19.
[13]Andreotti B.A two-species model of aeolian sand transport[J].Journal of Fluid Mechanics,2004,510,47-50.
[14]McEwan J K,Willetts B B,Rice M A.The grain/bed collision in sand transport by wind[J].Sedimentology,1992,39:971-981.
[15]Rioual F,Valance A,Bideau D.Experimental study of the collision process of a grain on a two-dimensional granular bed[J].Physical Review E,2000,62:2450-2459.
[16]Werner B T,Haff P K.The impact process in eolian saltation:two dimensional simulations[J].Sedimentology,1988,35:189-196.
[17]Iversen J D,Rasmussen K R.The effect of wind speed and bed slope on sand transport[J].Sedimentology,1999,46(4):723-731.
[18]Zhou Y H,Guo X,Zheng X J.Experimental measurement of wind-sand flux and sand transport for naturally mixed sands[J].Physical Review E.2002,66:021305.