栅栏沙丘表面流场的二维数值模拟
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摘要
数值模拟是研究风沙地貌形态动力学和风沙工程工作原理的有效途径.本文利用数值模拟方法,通过对比不同的迎风坡度以及迎风坡上部设置阻沙栅栏条件下的沙丘近地面流场特征,讨论了沙区道路防护体系前沿"栅栏沙丘"形成发育的流场条件.结果表明,随沙丘迎风坡坡度增大,背风坡回流区变高、变长,且坡度>15°后背风坡回流区流场基本不再变化.沙丘迎风坡阻沙栅栏的影响主要体现在气流的提前分离及其背风侧小涡的形成,回流区范围因叠加而变得更高、更远.这种流场变化特征对沙丘表面风沙过程具有显著影响,是形态趋于高大、断面趋于对称的栅栏沙丘形成发展的原因所在.
Numerical simulation is an effectual means to make clear the topographic dynamicsof aeolian landforms and blown sand control engineering.Making use of numericalsimulation and by comparing the near surface airflow field above different windwardslopes with or with no fence being set up at the upper windward slope,this paperdiscussed the airflow conditions for the formation and development of"fence dunes"thatexisted at the front edge of railway or highway protective systems in desert regions.Theresults show that backflow zone in the dune lee side gets higher and longer with theincrease of windward slope.When the windward slope is steeper than 15°,backflow fieldin the lee changes little.The main effects of the fence at the upper windward slope aredemonstrated by airflow separation in advance and the formation of small vortex in thelee side of the fence,which leads to the superimposition of backflow zone in the lee sideof the fence to that in the lee of the dune and therefore makes it higher and longer.Sucha reshaped airflow remarkably influences the aeolian processes on the dune andcontributes to the formation and development of the"fence dune"that is characterizedby growing height and approximately symmetric cross section.
Numerical simulation is an effectual means to make clear the topographic dynamicsof aeolian landforms and blown sand control engineering.Making use of numericalsimulation and by comparing the near surface airflow field above different windwardslopes with or with no fence being set up at the upper windward slope,this paperdiscussed the airflow conditions for the formation and development of"fence dunes"thatexisted at the front edge of railway or highway protective systems in desert regions.Theresults show that backflow zone in the dune lee side gets higher and longer with theincrease of windward slope.When the windward slope is steeper than 15°,backflow fieldin the lee changes little.The main effects of the fence at the upper windward slope aredemonstrated by airflow separation in advance and the formation of small vortex in thelee side of the fence,which leads to the superimposition of backflow zone in the lee sideof the fence to that in the lee of the dune and therefore makes it higher and longer.Sucha reshaped airflow remarkably influences the aeolian processes on the dune andcontributes to the formation and development of the"fence dune"that is characterizedby growing height and approximately symmetric cross section.
引文
[1]张克存,屈建军,牛清河,等.青藏铁路沿线阻沙栅栏防护机理及其效应分析[J].中国沙漠,2011,31(1):16-20Zhang Kecun,Qu Jianjun,Niu Qinghe,et al.Protective mechanism and efficiency of sand-blocking fences along Qinghai-Tibet railway[J].Journal of Desert Research,2011,31(1):16-20
[2]罗万银,董治宝,钱广强,等.直立阻沙栅栏流场特征的风洞模拟实验[J].中国沙漠,2009,29(2):200-205Luo Wanyin,Dong Zhibao,Qian Guangqiang,et al.Wind tunnel simulation on the flow characteristics around upright fences[J].Journal of Desert Research,2009,29(2):200-205
[3]马晓洁,张春来,张加琼,等.包兰铁路沙坡头段防护体系前沿栅栏沙丘形态与近地面流场[J].中国沙漠,2013,33(3):649-654Ma Xiaojie,Zhang Chunlai,Zhang Jiaqiong,et al.The morphology and near surface air flow field of fence dunes at the front of the railway protective system in Shapotou section of Baotou-Lanzhou railway[J].Journal of Desert Research,2013,33(3):649-654
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[10]Wilson J D,Yee E.Calculation of winds disturbed by an array of fences[J].Agricultural and Forest Meteorology,2003,115:31-50
[11]Santiago J L,Martin F,Cuerva A,et al.Experimental and numerical study of wind flow behind windbreaks[J].Atmospheric Environment,2007,41:6406-6420
[12]张春来,邹学勇,程宏,等.包兰铁路沙坡头段防护体系近地面流场特征[J].应用基础与工程科学学报,2006,14(3):353-360Zhang Chunlai,Zou Xueyong,Cheng Hong,et al.Near surface air flow field across the shelterbelt of Shapotou section,Baotou-Lanzhou line[J].Journal of Basic Science and Engineering,2006,14(3):353-360
[13]屈建军,凌裕泉,井哲帆,等.包兰铁路沙坡头段风沙运动规律及其与防护体系的相互作用[J].中国沙漠,2007,27(4):530-533Qu Jianjun,Ling Yuquan,Jing Zhefan,et al.Interaction between sand blown activity and protection system in Shapotou section of Baotou-Lanzhou railway[J].Journal of Desert Research,2007,27(4):530-533
[14]曾秋兰,李振山,卢傅安,等.高速公路透风型挡风墙不同位置防风特性的数值模拟研究[J].中国沙漠,2012,32(6):1542-1550Zeng Qiulan,Li Zhenshan,Lu Fuan,et al.A computational study of wind-break performance of ventilated windbreak wall in different locations on the highway[J].Journal of Desert Research,2012,32(6):1542-1550
[15]Spalart P R,Allmaras S.A one-equation turbulence model for aerodynamic flows[J].AIAA Paper.AIAA-1992-439,1992,doi:10.2514/6.1992-439
[16]郭永怀.边界层理论讲义[M].合肥:中国科学技术大学出版社,2008Guo Yonghuai.Handout of boundary layer theory[M].Hefei:Press of University of Science and Technology of China,2008
[17]哈斯.腾格里沙漠东南缘沙丘形态示量特征及其影响因素[J].中国沙漠,1995,15(2):136-142Hasi.Characteristics and controlling factors of dune morphometry in the southeastern fringe of Tengger Desert[J].Journal of Desert Research,1995,15(2):136-142
[2]罗万银,董治宝,钱广强,等.直立阻沙栅栏流场特征的风洞模拟实验[J].中国沙漠,2009,29(2):200-205Luo Wanyin,Dong Zhibao,Qian Guangqiang,et al.Wind tunnel simulation on the flow characteristics around upright fences[J].Journal of Desert Research,2009,29(2):200-205
[3]马晓洁,张春来,张加琼,等.包兰铁路沙坡头段防护体系前沿栅栏沙丘形态与近地面流场[J].中国沙漠,2013,33(3):649-654Ma Xiaojie,Zhang Chunlai,Zhang Jiaqiong,et al.The morphology and near surface air flow field of fence dunes at the front of the railway protective system in Shapotou section of Baotou-Lanzhou railway[J].Journal of Desert Research,2013,33(3):649-654
[4]Miao T D,Mu Q S,Wu S Z.Computer simulation of aeolian sand ripples and dunes[J].Physics Letters A,2001,288:16-22
[5]Anderson R S,Bunas K Z.Grain size segregation and stratigraphy in aeolian ripples modelled with a cellular automaton[J].Nature,1993,365:740-743
[6]Wilson J D.Numerical studies of flow through a windbreak[J].Journal of Wind Engineering and Industrial Aerodynamics,1985,21:119-154
[7]Wang H,Takle E S.A numerical simulation of boundary-layer flows near shelterbelts[J].Boundary-Layer Meteorology,1995,75:141-173
[8]Packwood A R.Flow through porous fences in thick boundary layers:Comparisons between laboratory and numerical experiments[J].Journal of Wind Engineering and Industrial Aerodynamics,2000,88:75-90
[9]Wang H,Takle E S,Shen J.Shelterbelts and windbreaks:Mathematical modeling and computer simulations of turbulent flows[J].Annual Review of Fluid Mechanics,2001,33:549-586
[10]Wilson J D,Yee E.Calculation of winds disturbed by an array of fences[J].Agricultural and Forest Meteorology,2003,115:31-50
[11]Santiago J L,Martin F,Cuerva A,et al.Experimental and numerical study of wind flow behind windbreaks[J].Atmospheric Environment,2007,41:6406-6420
[12]张春来,邹学勇,程宏,等.包兰铁路沙坡头段防护体系近地面流场特征[J].应用基础与工程科学学报,2006,14(3):353-360Zhang Chunlai,Zou Xueyong,Cheng Hong,et al.Near surface air flow field across the shelterbelt of Shapotou section,Baotou-Lanzhou line[J].Journal of Basic Science and Engineering,2006,14(3):353-360
[13]屈建军,凌裕泉,井哲帆,等.包兰铁路沙坡头段风沙运动规律及其与防护体系的相互作用[J].中国沙漠,2007,27(4):530-533Qu Jianjun,Ling Yuquan,Jing Zhefan,et al.Interaction between sand blown activity and protection system in Shapotou section of Baotou-Lanzhou railway[J].Journal of Desert Research,2007,27(4):530-533
[14]曾秋兰,李振山,卢傅安,等.高速公路透风型挡风墙不同位置防风特性的数值模拟研究[J].中国沙漠,2012,32(6):1542-1550Zeng Qiulan,Li Zhenshan,Lu Fuan,et al.A computational study of wind-break performance of ventilated windbreak wall in different locations on the highway[J].Journal of Desert Research,2012,32(6):1542-1550
[15]Spalart P R,Allmaras S.A one-equation turbulence model for aerodynamic flows[J].AIAA Paper.AIAA-1992-439,1992,doi:10.2514/6.1992-439
[16]郭永怀.边界层理论讲义[M].合肥:中国科学技术大学出版社,2008Guo Yonghuai.Handout of boundary layer theory[M].Hefei:Press of University of Science and Technology of China,2008
[17]哈斯.腾格里沙漠东南缘沙丘形态示量特征及其影响因素[J].中国沙漠,1995,15(2):136-142Hasi.Characteristics and controlling factors of dune morphometry in the southeastern fringe of Tengger Desert[J].Journal of Desert Research,1995,15(2):136-142
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