利用Fluent软件对植物坝覆盖区域流场的数值模拟

利用计算流体力学软件Fluent,用VOF方法追踪自由水面,对有植物坝覆盖的水槽二维两相流场进行数值模拟,采用多孔介质域模拟植物坝覆盖区域,以多孔介质前后压强配合孔隙率来确定渗透率。将数值计算得到的流速值与模型试验流速值实测结果进行比对,研究表明两者吻合较好。     

HYDRAULIC RESISTANCE OF SUBMERGED VEGETATION RELATED TO EFFECTIVE HEIGHT

Submerged vegetation has a significant impact on water flow velocity. Current investigations include the impact through adding drag resistance and increasing bottom roughness coefficient, which cannot elucidate the characters of real submerged vegetation. To evaluate the effects of submerged vegetation on water currents at different velocities, a laboratory experiment was conducted using three kinds of vegetations. The effective heights of these vegetations on varying flow velocities were evaluated. An equation describing the relationship between the normalized resistance of the submerged plants and the Reynolds number based on the plant effective height was then established and used to calculate the hydraulic resistance parameters of submerged plants in different stages of growth.     

近20年塔里木河干流生态环境变化遥感监测分析

针对塔里木河流域综合治理后生态环境的变化状况及植被的恢复状况等热点问题,基于遥感时空变化分析方法从土地利用、地表水体和植被覆盖度的时空变化方面分析了近20年来塔里木河干流生态环境的变化状况。结果表明:(1)塔里木河干流土地利用受到人类活动的影响显著,自2000年以来,塔里木河干流耕地面积增加显著,净增2 229 km²,草地面积整体下降,萎缩3 157 km²;(2)综合治理以来,下游河段2009—2018时段水体出现频率明显高于2000—2008时段,水体出现频率提高约15%;(3)2000年以来,塔里木河流域的植被覆盖度持续增加,特别是下游河段植被覆盖度增加明显,覆盖度增加18%。但中、上游流域的植被覆盖度的增加趋势主要贡献来源于耕地,中上游地区耕地的增加仍会对塔里木河流域的生态保护和恢复造成一定的影响。     

滦河上游植被指数NDVI及EVI对SPEI的响应差异

在全球气候变化和人类活动的双重影响下,干旱呈广发、频发态势,使植被生长受到限制,进而影响生态系统结构,威胁区域生态安全。以滦河上游为研究区,基于2000-2019年归一化植被指数NDVI和增强型植被指数EVI,并结合标准化降水蒸散指数SPEI,分析滦河上游气象干旱和植被生长状况的变化趋势及空间分布特征,探讨植被变化对多时间尺度SPEI指数的响应差异。结果表明：近20年滦河上游SPEI呈波动式增大趋势,年尺度SPEI增大速率为0.040 1/a;干旱面积总体减少,减少速率为-1.430 4％/a;NDVI和EVI空间分布特征和变化趋势大体一致,植被覆盖度呈东南高西北低的特征,NDVI和EVI增大速率分别达0.027/a和0.026/a;大部分区域SPEI与植被指数呈正相关,其中NDVI对SPEI-3的响应最强,EVI对SPEI-6的响应最强,总体上EVI与SPEI的相关性强于NDVI;草地对气象干旱最敏感,农田次之,林地最弱。     

基于MODIS数据的浙江省植被覆盖度时空变化分析

以浙江省为研究区,基于2009-2018年MODIS_NDVI数据,采用MVC最大值合成法获取逐月NDVI值,利用改进的像元二分模型估算2009-2018年植被覆盖度,结合DEM数据及《浙江省林地保护利用规划》(2010-2020年)中的林地分区,分析浙江省植被覆盖度的时空变化情况.结果 表明:①2009-2018年浙...     

不同植被类型对堆积体坡面径流特性的影响

针对植被防护堆积体侵蚀动力机制的问题,通过野外模拟降雨试验,分析直根系和须根系植被对堆积体径流流速、水力和水动力参数的影响.结果表明:植被削减堆积体平均侵蚀速率达88.34％～92.88％,直根系消减平均流速效益为50.51％,须根系为21.32％～35.61％;裸坡和植被堆积体径流流型均属于层流(雷诺数<40),裸坡...     

TTI hydraulics and erosion control laboratory research field performance of erosion-control blankets

Storm water management issues facing the Texas Department of Transportation in the late 1980s led to the development of a coordinated research program with the Texas Transportation Institute. Researchers developed methodologies for evaluating the field performance of various erosion control technologies of the most widely used products within the Department's construction and maintenance operations. From these methodologies, the Hydraulics and Erosion Control Laboratory was designed and constructed. Currently, participants include private industry (manufacturers of erosion control products), transportation researchers (TTI), and the public sector (TxDOT).The results reported in this paper reflect 2 years of erosion-control blanket research. The study objectives were to determine the effectiveness of erosion-control blankets on the growth of warm-season perennial grasses and their ability to prevent sediment loss in a sloped condition.The laboratory simulates the highway environment with the sloped plots (6 m in width) located on an earthen embankment that is 300 m in length and 6.75 m in height (94 ft. by 22 ft., vertically). A randomized experimental design was replicated on two soil types (sand and clay) for each slope condition (3:1 or 2:1) with a control.In general, the results indicate better combined results relating to sediment retention and vegetation establishment performance for erosion-control blankets on sandy soils (noncohesive) regardless of slope condition (3:1 or 2:1) or material type. A minimum of 50% more sediment was retained on the sandy treatment plots and a 45% more vegetation coverage was achieved compared with the control plots. When analyzed by material type related to performance, excelsior, synthetic blends, and straw/coconut blends performed the best. For clay soils (cohesive), regardless of slope condition (3:1 or 2:1), the combined results indicate a minimum of 75% more sediment was retained and a minimum of 5% more vegetation establishment was achieved compared with the control plots. When analyzed by material type related to performance, excelsior, straw, and straw/coconut blends performed the best.     

“盆”“山”耦合和脱耦的反转点和切入点研究

反转构造的反转点和“盆”“山”关系的切入点是“盆”“山”耦合和脱耦研究的方法论中的关键问题。抓准抓好反转点,一是要深刻认识中国大地构造特征所决定的“盆”“山”关系的复杂性,二是要全面了解区域内“盆”“山”耦合和脱耦的关键问题。“盆”“山”关系的切入点,既应视具体的研究对象多方位、多角度、多层次、多侧面地确定,也要强调首要的和必要的切入点是造山作用的类型。抓对反转点的必由途径是“盆”“山”研究中把“正序”与“反序”结合起来而以“反序”的研究为主,文章简要介绍了反序地编制“盆”“山”演化图的经验。反转点和切入点的确定体现在盆地研究中,是在给予时间约束和厘定盆地含义的前提下正确认识盆地的世代更迭和各世代的构造格架及构造样式,特别是正确认识重大构造运动时期的盆地世代更迭。“盆”“山”耦合和脱耦的反转点和切入点研究的突破,必将造成盆地研究生动活泼的新局面,进而给残留海相盆地的油气勘探带来新的启示。     

海底石油管线防护技术研究

基于海洋石油平台和海底管线的基础冲淘原理和特征的分析,探讨了仿生植物增阻拦沙的机理,建立了植物底床剪应力计算关系;借助正态模型试验和抛石防护对比试验研究,证明仿生植物具有良好的防护功效。     

卡拉贝利水库对河流末端地下水埋深的影响

重点水利枢纽工程区域环境现状、发展趋势及水库运行对环境可能产生的影响是环境影响评价工作的重要组成部分。本文分析了克孜河下游河岸林草区的水分运动和补给关系,计算地下水补给量变化值和埋深变化值,预测卡拉贝利水库修建后天然植被的生长状况,为项目决策和工程环境管理提供科学的依据。通过建立区域水均衡模型,模拟工程修建前后,区域地表水与地下水的水量分配和流转关系及平衡状况变化,通过监测研究区地下水埋深数据,模拟工程建成前后河流末端河岸带林草区地下水埋深的分布变化情况,分析由于工程建设导致地下水位变化进而对河岸带林草的影响。结果表明:研究区总体上是河道地表径流补给地下水,河道过水期水面线高于地下水位,河道地表径流与地下水的补给关系是地表水补给地下水,在断流期河道两岸地下水位高于河床高程,地下水侧向渗出补给地表水。