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Pattern analysis of a linear dune field on the northern margin of Qarhan Salt Lake,northwestern China

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Journal of Arid Land 2016年第5期8卷 670-680页

作者： LI Jiyan dong zhibao qian guangqiang ZHANG Zhengcai luo wanyin LU Junfeng wang Meng Taiyuan Normal University Jinzhong 030619 China Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

In terms of formation mechanisms of linear dunes,there are open arguments for their widespread distribution and multi-morphological *** order to clarify the formation mechanism of linear dunes of Qarhan Salt Lake,we used pattern analysis method to analyze the statistical characteristics and spatial variation of their pattern *** at the west-northwest margin,the pattern parameters showed regular spatial variation from the up-middle part towards the downwind end of the dune *** on the cumulative probability plots for inter-crest spacing and crest length,we divided the linear dunes into three groups,which corresponding to the three evolution stages of these *** first group comprises erosional relics,with shorter crests,smaller inter-crest spacing and more random dune *** second group comprises dunes whose sand supply is just sufficient to maintain stability and these dunes are approaching the net erosion *** crest length and inter-crest spacing of these dunes are much larger than those of the first group,and dune orientation is closer to the resultant drift direction （RDD） .The last group comprises linear dunes that are still undergoing vertical accretion and longitudinal elongation,which follows the RDD of the modern wind *** presence of regular spatial variation of pattern parameters and a similar geometry with the vegetated linear dunes suggest that deposition and erosion coexist in the development and evolution of linear dunes of Qarhan Salt Lake,*** predominates at the downwind end of linear dunes in the vertical accretion and longitudinal elongation stage,whereas erosion mainly occurs at the upwind end of linear dunes in the degradation ***,the formation mechanism of linear dunes in Qarhan Salt Lake can be reasonably explained by the combination of depositional and erosional theories.

关键词： pattern analysis self-organization linear dunes dune field Qarhan Salt Lake Qaidam Basin

Threshold wind velocity in the lee of two-dimensional transverse dunes

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Research in Cold and Arid Regions 2010年第1期2卷 1-6页

作者： zhibao dong hongtao wang guangqiang qian wanyin luo Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou Gansu 730000 China

Secondary flow plays an important role in the development of dunes. To investigate this phenomenon, we simulated models of transverse dunes with different stoss slopes in a wind tunnel. We measured the threshold wind velocity at different locations in the lee of the dunes, and observed the corresponding particle movement characteristics under threshold conditions to assess the sedi-mentological significance of secondary airflow. Threshold wind velocity changed with both horizontal distance and stoss slope. Its variation with horizontal distance is characterized by a region in which a rapid reduction occurs, a region with a minimum value, and a region with high value. We confirmed the presence of reversal cells, irrespective of the stoss slope. Neither the variation in threshold wind velocity nor the variation in reattachment distance as a function of stoss slope followed a monotonic function. The 15° stoss slope had the greatest threshold wind velocity and reattachment distance.

关键词： Aeolian geomoephology dune dynamics transverse dunes

A Wind Tunnel Investigation of the Shear Stress with A Blowing Sand Cloud

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Research in Cold and Arid Regions 2008年第1期 42-58页

In a blowing sand system,the wind provides the driving forces for the particle movement while the moving particles exert the opposite forces to the wind by extracting its *** wind-sand interaction that can be characterized by shear stress and force exerted on the wind by moving particles results in the modification of wind *** wind pro-files re-adapted to blown sand movement are measured in a wind tunnel for different grain size populations and at differ-ent free-stream wind *** shear stress with a blowing sand cloud and force exerted on the wind by moving par-ticles are calculated from the measured wind velocity *** results suggest that the wind profiles with presence of blowing sand cloud assume convex-upward curves on the u(z)-ln(z) plot compared with the straight lines characterizing the velocity profiles of clean wind,and they can be better fitted by power function than log-linear *** exponent of the power function ranging from 0.1 to 0.17 tends to increase with an increase in wind velocity but decrease with an increase in particle *** force per unit volume exerted on the wind by blown sand drift that is calculated based on the empirical power functions for the wind velocity profiles is found to decrease with *** particle-induced force makes the total shear stress with blowing sand cloud partitioned into air-borne stress that results from the wind velocity gradient and grain-borne stress that results from the upward or downward movement of *** air-borne stress in-creases with an increase in height,while the grain-borne stress decreases with an increase in *** air-borne shear stress at the top of sand cloud layer increases with both wind velocity and grain size,implying that it increases with sand transport rate for a given grain *** shear stress with a blowing sand cloud is also closely related to the sand transport *** the total shear stress and grain-borne stress on th

关键词： aeolian transport wind-sand interaction air-borne stress grain-borne stress

Momentum profile of aeolian saltation cloud

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Research in Cold and Arid Regions 2009年第1期1卷 25-29页

作者： zhibao dong wanyin luo guangqiang qian hongtao wang Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of SciencesLanzhouGansu 730000China

The momentum profile of an aeolian saltation cloud is poorly understood. In this paper, height profiles for saltation momentum are reconstructed for three particle-size populations at four wind velocities based on profiles for mean particle velocity and relative particle concentration of saltation cloud obtained using particle image velocimetry in a wind tunnel. The results suggest that the saltation momentum profiles are characterized by peak curves with a maximum at some height above the surface. The height of this maximum increases with increasing wind velocity, but decreases with increasing particle size. It is linearly correlated with average saltation height and is comparable with the results of numerical simulations in a previous study. Our results confirm that Bagnold’s kink is an important feature of wind velocity profiles modified by the presence of saltating particles and that the height of the kink is closely related to the average trajectories of the saltating particles.

关键词： aeolian saltation cloud momentum profile wind tunnel test

基于3S的豫北内黄县近30年来植被覆被变化研究

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地域研究与开发 2010年第4期29卷 127-130,144页

作者：李根明董治宝孙虎钱广强罗万银王洪涛逯军峰中国科学院寒区旱区环境与工程研究所沙漠与沙漠化重点实验室兰州730000 陕西师范大学旅游与环境学院西安710006

运用3S技术,分析和探讨了河南省内黄县1979—2007年的植被覆盖度变化特征。结果显示,该区30年间的植被覆盖度变化显著。具体为：高覆盖度和中高覆盖度逐年上升,而中覆盖度、低覆盖度和极低覆盖度出现不同程度的降低,中覆盖度降低的幅度... 详细信息

运用3S技术,分析和探讨了河南省内黄县1979—2007年的植被覆盖度变化特征。结果显示,该区30年间的植被覆盖度变化显著。具体为：高覆盖度和中高覆盖度逐年上升,而中覆盖度、低覆盖度和极低覆盖度出现不同程度的降低,中覆盖度降低的幅度较小,而低级覆盖度下降幅度较大。结论表明研究区的生态环境质量呈现不断上升的态势。一方面反映了人口增长和经济建设需求对植被覆被变化的积极影响,另一方面反映相关部门重视生态环境的建设,研究区人口素质提高环保意识增强。

关键词：植被覆盖度 3S 生态环境质量内黄县

共和盆地高寒草原风蚀坑表层沉积物粒度特征及动力学意义

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中国沙漠 2017年第1期37卷 7-16页

作者：王中原罗万银董治宝逯军峰钱广强徐贵江中科院寒区旱区环境与工程研究所沙漠与沙漠化重点实验室甘肃兰州730000 中国科学院大学北京100049

风蚀坑是高寒地区草原沙漠化的起点,气流对坑内沙物质的侵蚀、搬运和堆积为沙漠化进程提供了重要的物源。以共和盆地龙羊峡水库上游黄河阶地高寒草原上不同发育阶段的风蚀坑为研究对象,通过分析表层沉积物的粒度组成特征,比较风蚀坑表... 详细信息

风蚀坑是高寒地区草原沙漠化的起点,气流对坑内沙物质的侵蚀、搬运和堆积为沙漠化进程提供了重要的物源。以共和盆地龙羊峡水库上游黄河阶地高寒草原上不同发育阶段的风蚀坑为研究对象,通过分析表层沉积物的粒度组成特征,比较风蚀坑表层沉积物粒度组成随坑体形态和地貌部位的变化趋势,探讨风蚀坑内沉积物的粒度分异在其形成演化过程中的动力学意义。结果表明:风蚀坑表面沉积物来源主要是古风沙沉积物。尽管研究区风蚀坑空间尺度相差很大,但因为动力学过程的相似性,沉积物粒度变化依然在宏观尺度上表现出了一致性。随着风蚀坑面积扩大,在积沙区迎风坡的中下部以及坑底部位粗沙、极粗沙成分显著增多。与此同时,沉积物分选性变差,表层沉积物分布模式由单峰态渐趋向多峰,粒度参数变幅明显增大。受盆地内盛行风以及坡向影响,风蚀坑两侧侵蚀壁受侵蚀程度差异明显,东北壁受到了更强的风力掏蚀且分选性更好。沉积物粒度分析作为风沙地貌学的基础性工作,也为高寒草原风蚀坑的发育演变、空气动力学过程等后续研究提供了基础参数。

关键词：风蚀坑粒度组成高寒草原沙漠化空气动力学

基于原位风沙流观测的广冲击角的溅射函数构建

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中国沙漠 2024年第5期44卷 254-260页

作者：蒋缠文董治宝罗万银钱广强张正偲逯军峰王晓艳渭南师范学院环境与生命科学学院/陕西省河流湿地生态与环境重点实验室陕西渭南714000 陕西师范大学地理科学与旅游学院陕西西安710119 中国科学院西北生态环境资源研究院甘肃兰州730000

风沙流中沙粒与床面的相互作用机理是风沙物理学研究的关键问题。由于沙粒运动的复杂性,数值模拟的研究结果通常与实际情况存在较大差异,因此,以实验手段得到的击溅函数对于理解粒-床碰撞的物理过程具有重要意义。基于饱和风沙流内气流... 详细信息

风沙流中沙粒与床面的相互作用机理是风沙物理学研究的关键问题。由于沙粒运动的复杂性,数值模拟的研究结果通常与实际情况存在较大差异,因此,以实验手段得到的击溅函数对于理解粒-床碰撞的物理过程具有重要意义。基于饱和风沙流内气流对碰撞过程的影响可以忽略不计的共识,学者们通过大量的无风碰撞实验进行击溅函数研究。然而,由于测量技术的限制,典型冲击角度(10°)下的粒-床碰撞过程的实测数据很少。鉴于数值模拟和无风碰撞实验都表明击溅函数对冲击角度较为敏感,基于高速摄影技术在风洞内获得了松散沙床表面大量冲击角在10°左右的粒-床碰撞过程,并结合前人沙粒离心发射器(冲击角20°~50°)的实验结果,构建了涵盖广泛冲击角度的溅射函数,这些函数能够适用于前人不同实验条件的风洞实验结果,这对未来的风沙物理学研究具有重要意义。

关键词：击溅函数跃移运动风洞实验粒-床碰撞过程高速摄影技术

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基于数字化轨迹的跃移粒子群速度剖面研究

中国沙漠 2024年第6期44卷 231-239页

研究跃移运动时,速度是一个重要参数。采用高速摄影技术在风洞中获得了松散沙面上跃移沙粒在上升段和降落段的平均速度垂直剖面。结果表明:垂直方向上的颗粒湍流强度高于水平方向1~2个数量级,造成颗粒速度在水平方向上很好地服从正态分... 详细信息

研究跃移运动时,速度是一个重要参数。采用高速摄影技术在风洞中获得了松散沙面上跃移沙粒在上升段和降落段的平均速度垂直剖面。结果表明:垂直方向上的颗粒湍流强度高于水平方向1~2个数量级,造成颗粒速度在水平方向上很好地服从正态分布,而在垂直方向上则较为分散且范围较窄(0~1 m·s^(-1))。同一高度处,降落段的平均水平速度是上升段的1.6~1.8倍,而降落段的垂直速度则略小于上升段。两段的相对平均水平速度(v_(x)/√gd,g为重力加速度,d为颗粒粒径)均与相对高度(z/Z,z为距床面高度,Z为边界层厚度)的平方根以及相对风速(u_(*)/u_(*ti),u_(*)为摩阻风速,u_(*ti)为冲击阈值)呈正比。上升段和降落段的平均垂直速度总体上均呈现随高度略微增加的趋势。上升段的平均垂直速度略高于降落段。平均垂直速度分布模式以及随高度变化特征的潜在机制需要通过进一步研究来阐明。

关键词：风沙跃移平均速度垂直变化数字化轨迹高速摄影技术