乌兰布和沙漠风沙流结构的研究

作者观测了固定、流动沙丘风沙流结构,并运用拟合曲线、拟合方程等方法对固定、流动沙丘风沙流结构进行了分析研究。结果表明,两种沙丘输沙率均与风速成正比,与高度成反比;0-40cm高度内输沙量与风速之间遵循指数关系;流动沙丘的沙粒运动主要集中在近地层0-6cm高度范围内;另外,植被阻截沉沙效果特别明显,植被覆盖度在30%时,沉沙效果达到95%以上,且随风速的增大而增加。     

沙质地表与砾质戈壁风沙运动对比研究——以敦煌莫高窟窟顶风沙运动为例

通过野外观测资料分析,阐明在沙质地表下,风速相当时不同风向风沙流的结构不同,即含沙量影响风沙流结构.一般随着含沙量的增大,各层的绝对输沙量相应增加,相对输沙量在下层增加,上层减少.但也有不一致的情况,本次野外观测就出现了下层减少上层增加的情况.戈壁风沙流结构与沙质地表显著不同,其风沙流结构呈独特的"象鼻"效应,即在一定高度有一个最大输沙量,且这个高度随风速的增大而增加.西北风作用下,自鸣沙山至窟顶输沙量逐渐减少.戈壁具有一定的阻沙效应,风速为7.7 m/s时,每100 m阻沙率达10%左右.沙山前沿固沙带对输沙量起着重要作用,有防护措施与无防护设施相比较,西北风的输沙量可减少95%左右.偏东北风在缺少沙源的情况下,主要以输送为主,偏南风实际输沙量明显小于偏西北风,输沙量由沙源地到窟区逐渐减少.     

毛乌素沙地风沙流结构的研究

运用曲线拟合、拟合方程等方法,对毛乌素沙地南缘流动沙丘0～30cm垂直高度范围内的风沙流结构进行了分析研究。结果表明:在0～30cm高度,输沙率均与风速成正比,与高度成反比,幂函数拟合关系最佳。其中,各高度层输沙率随风速的变化分别呈幂函数或指数函数关系,同风速下输沙率随着高度的增加而减小,呈幂函数或指数函数关系;随着风速和气流中总输沙率的增加,0～30cm高度范围内的绝对输沙率增加,相对输沙率(%)的变化为下层趋于减少,中层略变,上层增加,风沙流结构的特征值λ增大;风沙流中沙粒粒度沿垂向变化为细沙增加,中沙减少,沙粒平均粒径变细。     

沙漠公路防护林不同林带位置的风沙流结构

利用BSNE集沙仪对沙漠公路两侧防护林的近地表风沙流结构进行研究,结果表明:(1)随着高度的增加,不同林带位置上部的输沙量趋于一致,各点风沙流输沙量差异主要集中在近地表处,而植被覆盖与否对近地表气流中的输沙量有决定性作用,输沙量表现为:迎风面流沙地林带间背风面林带内。(2)迎风面及流沙地风沙流输沙量主要分布在距地表20 cm高度内,背风面则集中分布在50 cm高度内,均占观测高度输沙总量的74%以上,林带间及林带内风沙流输沙量在各高度层分布较为平均,介于11%~23%之间。(3)护林体系外(迎风面、背风面及流沙地),风沙流输沙垂直分布差异很大,输沙量随高度增加呈幂函数形式降低,而防护林体系内(林带间及林带内),风沙流垂直分布差异趋于减小,输沙量随高度增加呈多项式形式先降低后增加。     

塔克拉玛干沙漠北缘荒漠过渡带风沙流结构特征分析

利用多种集沙仪,通过野外实时输沙观测,对塔克拉玛干沙漠北缘荒漠过渡带的地表风沙流特征进行了分析,结果表明：① 100 cm高度范围内,总输沙量的47.3%分布在30 cm高度内,这一比例小于前人的研究结果;输沙量随高度的变化比较符合幂函数分布。② 风沙流输沙的粒径以细砂、极细砂与粉砂为主,各高度层所占比例均达99%以上;风沙流输沙平均粒径随高度增加而减小,沙尘的含量随高度增加呈现“象鼻”状分布。③ 风沙流中贴地层风速廓线受风沙相互作用的影响,不再符合对数分布,更加符合幂函数u=az^b分布。     

呼伦贝尔沙质草原风蚀坑地表风沙流结构特征

在呼伦贝尔沙质草原北部沙带中段风蚀坑集中分布区内,选取不同发育阶段的风蚀坑,通过同步观测风蚀坑地表(0～200 cm)风速及输沙通量,分析并比较风沙流结构特征,为呼伦贝尔沙质草原风蚀坑治理提供理论依据。研究表明:在裸地沙斑、活跃发展、固定阶段及重新活化阶段的风蚀坑,风速廓线基本遵循对数分布规律;而在未风蚀草地、消亡阶段的风蚀坑,气流受下垫面扰动,呈"S"形分布。风蚀坑各发育阶段输沙量与高度的最优拟合模型为负指数模型,不同发育阶段风蚀坑内部风沙流输沙量差异较为明显;超过95%的输沙量均在地表0～30 cm高度内,且63. 97%～90. 96%的输沙量集中分布在距地表10 cm高度内。风沙流跃移高度与风速正相关,依次为:活跃发展重新活化裸地沙斑固定阶段消亡阶段未风蚀草地。通过分析风沙流通量系数,可知在裸地沙斑、活跃发展及重新活化阶段,输沙量有向高层移动的趋势;而在其他阶段,由于植被盖度较高,使得风沙流多集中在近地层。     

锡林郭勒典型草原区平坦草地风雪流结构特征

通过对锡林郭勒典型草原区平坦草地积雪全覆盖状况下风雪流野外观测,分析了近地表100 cm高度内的风雪流结构。结果表明:风雪流结构表现为移雪强度随距离雪面高度增加而急剧减弱。风雪流活动范围随着2 m处风速增强而逐步增大。风雪流结构函数在低风速条件下(4~7 m·s~(-1))符合对数函数关系衰减,高风速条件下(8 m·s~(-1))呈幂函数关系衰减;风雪流搬运高度主要集中在近地表20 cm范围内,该高度内移雪量达到总移雪量的80%以上;近地表100 cm高度范围内的平均移雪强度与2 m处风速符合极显著的幂函数关系,关系式为Q=3.378 6×10~(-7)·V~(5.5390)(P0.001,R~2=0.972 9)。近地表风速的增加,会导致风雪流搬运能力的急剧增强。相关结论可为典型草原区风雪流防治提供理论依据。     

乌兰布和沙漠沿黄段不同治理措施的风沙运移特征及其防护效果

为科学治理黄河乌兰布和沙漠沿岸风沙入黄问题,以该河段沿线流沙为对照,开展了麦草沙障、沙柳沙障、葵花杆沙障和梭梭林为代表的工程与植物固沙实验,对不同治理措施下的风速廓线、粗糙度、风沙流结构、防护效果及其相互关系进行了野外观测与室内分析。结果表明:1)各沙障和梭梭林内风速廓线发生改变,近地表风速显著降低,地表粗糙度和摩阻风速显著增加。2)流沙表面输沙量分布随高度增加呈对数递减,90%集中在0~10cm范围,98%分布在0~30m范围内。3)不同措施的输沙率随风速的增加呈增加趋势,但输沙率仅为流沙的1.07%~38.27%,可很好的控制近地表的流沙活动。4)各类固沙措施的实施效果排序葵花杆沙障>梭梭林>沙柳沙障>麦草沙障,控制流沙效果均达到75%以上,对固定流沙均能起到积极作用。综合考虑固沙效果、成本、运输以及使用寿命等,该地区选择葵花杆沙障和梭梭较为合适。该研究结果可为解决风沙入黄问题、完善黄河沿岸风沙防护体系提供参考。     

保护性耕作农田风沙流空间分布规律研究

为了解保护性耕作农田风沙流的空间分布规律,对保护性耕作农田进行了野外风洞原位风蚀测试.结果表明:保护性耕作农田在不同风速下各高度的风沙流水平分布符合三次多项式规律,经过27行残茬、5.5 m的水平距离风沙流基本达到了平衡稳定状态;在垂直方向上风沙流分布符合高阶多项式规律,具有与砾石戈壁地表输沙量垂直分布极为相似的"象鼻"效应.试验还发现保护性耕作农田风沙流主要活动在近地表40 cm高度以下范围,占到风蚀物总质量的90%左右.     

巴丹吉林沙漠拐子湖地区贴地层风速廓线和风沙流结构特征

野外监测试验表明：自由风和风沙流廓线拟合虽都以Z=A·exp(-X/T)+Z₁形式分布,但在风沙流中拟合系数更高;风沙流结构中,在20 cm以下随着高度的增加,各高度的输沙率百分比、含沙浓度、运动颗粒能量都呈增大趋势;20 cm以上随高度增加,各高度输沙率百分比变小,输沙率占总输沙率的51%左右,含沙量主要集中在离地面20 cm以内;风沙流在垂直方向上,高度与含沙平均粒径呈负相关,风速与含沙平均粒径变化呈正相关。这些结论对拐子湖地区防风治沙有重要的指导意义。     

基于SPH方法的风沙流运动特性研究

文中基于光滑粒子流体动力学(Smoothed Particle Hydrodynamics:SPH)方法,采用五次样条光滑函数,通过调节不同类型粒子光滑因子,对风沙流运动特性进行分析:1)在风沙流起动阶段,沙粒平均水平速度随高度增加而增大,同一高度处沙粒平均水平速度随时间推移而减小。2)风沙流稳定前后,沙粒数均随高度的增加而减少。3)风沙流形成过程中气体粒子在计算域中心位置产生涡流,并随着时间推移,涡流又出现在计算域中上及右下方位置。4)起沙前后气体脉动强度随摩阻风速增加而增加,随高度增加呈现不同变化。结果表明:该方法模拟精度较高,适用于解决风沙两相流数值模拟问题。     

采煤塌陷对固定沙丘土壤水分动态的影响研究

通过对毛乌素沙地东南边缘沙地采煤塌陷对固定沙丘的水分时空动态分布规律影响的研究表明,沙土含水量的时空变化与降雨季节和降雨量有密切关系。沙丘0-80cm土层为土壤水分受降雨影响的活跃层,其中0-40cm土层变化最为明显。沙丘的迎风坡和坡顶含水量低于沙区的其他部位,但受沙丘高度以及植被和土壤质地的影响这种差异并不明显。在沙区采煤引起的地表塌陷对土壤水分的时空变化影响较小。     

龙羊峡水库周围风沙流的观测、计算及对库区的影响

为估计龙羊峡水库进库风沙量及其对库区的影响,在库西北流沙带进行了长达一年的风沙观测。并在分析观测数据的基础上总结出了计算断面输沙率的通用经验公式,也给出了断面通量系数、起沙风速和粒径之间的关系。用所得公式算出年均进库风沙量为141万立方米,它对库容的影响可不计,但将严重危害农牧业生产和地面设施,也会污染环境。     

Effect of the W-beam central guardrails on wind-blown sand deposition on desert expressways in sandy regions

Many desert expressways are affected by the deposition of the wind-blown sand,which might block the movement of vehicles or cause accidents.W-beam central guardrails,which are used to improve the safety of desert expressways,are thought to influence the deposition of the wind-blown sand,but this has yet not to be studied adequately.To address this issue,we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow,the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions.The subgrade model is 3.5 cm high and 80.0 cm wide,with a bank slope ratio of 1:3.The W-beam central guardrails model is 3.7 cm high,which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column.The wind velocity was measured by using pitot-static tubes placed at nine different heights(1,2,3,5,7,10,15,30 and 50 cm)above the floor of the chamber.The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler,which was sectioned into 20 intervals.In addition,we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016,by using a customized 78-cm-high gradient sand sampler for the sand flux structure test.Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade,and the wind velocity on the leeward side weakens significantly.The W-beam central guardrails decrease the leeward wind velocity,whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails.The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails.At 0.0H and 0.5H(where H=3.5 cm,which is the height of the subgrade),the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails,and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface.The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height.The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points,which is consistent with the position of the minimum wind velocity in the wind tunnel test.The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.     

Impact of utility-scale solar photovoltaic array on the aeolian sediment transport in Hobq Desert,China

Deserts are ideal places to develop ground-mounted large-scale solar photovoltaic (PV) powerstation. Unfortunately, solar energy production, operation, and maintenance are affected bygeomorphological changes caused by surface erosion that may occur after the construction of the solar PVpower station. In order to avoid damage to a solar PV power station in sandy areas, it is necessary toinvestigate the characteristics of wind-sand movement under the interference of solar PV array. The studywas undertaken by measuring sediment transport of different wind directions above shifting dunes andthree observation sites around the PV panels in the Hobq Desert, China. The results showed that the twoparameterexponential function provides better fit for the measured flux density profiles to the near-surfaceof solar PV array. However, the saltation height of sand particles changes with the intersection anglebetween the solar PV array and wind direction exceed 45°. The sediment transport rate above shifting duneswas always the greatest, while that around the test PV panels varied accordingly to the wind direction.Moreover, the aeolian sediment transport on the solar PV array was significantly affected by wind direction.The value of sand inhibition rate ranged from 35.46% to 88.51% at different wind directions. When theintersection angle exceeds 45°, the mean value of sediment transport rate above the solar PV array reducesto 82.58% compared with the shifting dunes. The results of our study expand our understanding of theformation and evolution of aeolian geomorphology at the solar PV footprint. This will facilitate the designand control engineering plans for solar PV array in sandy areas that operate according to the wind regime.     

戈壁、流沙地表风沙流特性研究

通过对戈壁、流沙地表风沙流特性的风洞模拟实验研究,风沙流中的风速廓线分布满足幂函数的形式,其幂指数在0.20左右。对于戈壁地表,在不同风速下,相同高度层含沙量具有很大的相关性,风沙活动层主要集中在距地表20cm范围内;由于沙粒与戈壁地表的砾石发生碰撞,风沙流不再服从对数关系递减,其极值出现的高度随风速的增加而上移,呈现"象鼻效应"。     

Optimization designs of artificial facilities in deserts based on computational simulation

Sediment transport of sand particles by wind is one of the main processes leading todesertification in arid regions, which severely impairs the ability of mankind to produce and live by driftingsand into settlements. Optimization designs of artificial facilities have lately attracted extensive interest forhuman settlement systems in deserts because of their acceptable protection effect, convenience ofimplementation, and low material cost. However, the complexity of a settlement system poses challengesconcerning finding suitable materials, artificial facilities, and optimization designs for sand depositionprotection. In an effort to overcome these challenges, we propose a settlement system built with brick, solarpanel, and building arrays to meet the basic needs of human settlements in arid regions while preventingwind-sand disasters. The wind flow and movement characteristics of sand particles in the brick, panel, andbuilding arrays were calculated using computational fluid dynamics and discrete phase model. Theperformance of three types of arrays in wind-sand flow in terms of decreasing the wind velocity and sandparticleinvasion distance was evaluated. The results show that the wind velocity near the surface and thesand invasion distance were significantly decreased in the space between the brick arrays through properlyselected vertical size and interspaces, indicating that the brick arrays have an impressive sand fixing andblocking performance;their effective protection distance was 3–4 m. The building arrays increased the nearsurfacewind velocity among buildings, resulting in less deposition of sand particles. The solar panel arrayswere similar to the building arrays in most cases, but the deposition of sand particles on solar panels exerteda negative effect on energy utilization efficiency. Therefore, taking the optimal configuration of thesettlement system into consideration, this study concludes that (1) brick arrays, which were proven effectivein preventing sand particles, must be arranged in an upwind area;(2) solar panel arrays could accelerate thewind flow, so they are best to be arranged at the place where sand particles deposited easily;and (3) buildingarrays present a better arrangement in downwind areas.     

Sand source and formation mechanism of riverine sand dunes: a case study in Xiangshui River,China

Riverine sand dunes develop as a result of fluvial-aeolian interactions. The primarily barchan dune chains along the Xiangshui River (a branch of the Xar Moron River in the western part of the Horqin Sandy Land of China) form a typical riverine dune field. We collected a series of samples from the riverine sand dunes parallel to the direction of the prevailing wind and investigated the sand sources and formation mechanisms of these dunes by determining the grain size, heavy mineral content and optically stimulated luminescence (OSL) of the samples. The sand of the near-river dunes was coarser than the sand of the dunes distant from the river, indicating that coarse sand of the valley mainly deposited on near-river dunes. The heavy mineral analysis suggested that wind-sand activity levels were intense on the upwind dunes, but relatively weak on the downwind dunes. This indicated that the sand sources for the near-river dunes were more abundant than those of the distant dunes. Our OSL analysis of samples suggested that the deposition rates on dunes near the river were greater than the deposition rates on dunes distant from the river. The development of dunes along the river indicated that the river played an important role in dune formation and development. In addition, airflow fluctuation and the formation of the waveform dunes had a type of feedback relationship. Grain size, heavy mineral and OSL analyses are widely used methods in wind-sand research. Sand dune grain size characteristics reflect the effects of airflow on the transport and separation of sand materials, as well as the physical characteristics of the sand sources. Heavy mineral characteristics are often used to investigate the relationships between sediments and sand sources. OSL indicates dune age, revealing formation of dunes. Therefore, it is useful to explore dune sand sources, as well as the mechanisms underlying dune formation, by determining grain size, heavy mineral content and OSL. This study investigated the sand sources of riverine dunes and provided new information about riverine dune formation and development.