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题名	柽柳灌丛沙堆风沙动力学过程的风洞实验
作者	谭凤翥
答辩日期	2017-05-01
文献子类	硕士
授予单位	中国科学院大学
授予地点	新疆乌鲁木齐
导师	王雪芹
关键词	柽柳灌丛沙堆 三维流场 蚀积强度 风沙流结构 临界植被盖度 风洞实验 Tamarix ramosissima nebkhas three-dimensional airflow patterns erosion intensity wind-sand flow structure critical vegetation coverage wind tunnel simulation
学位专业	工程硕士
英文摘要	The study took the Tamarix nebkhas and interdune plants, which are widelydistributed in oasis-desert ecotone at the southern rim of the Taklimakan desert, as theresearch prototype to make five sets of nebkhas model with background vegetationcoverage of 0%, 4%, 10%, 16% and 26% respectively to conduct the simulationexperiment of airflow patterns and erosion and accumulation change rule in the windtunnel. The wind flow field, surface alteration, surface aerodynamics, sedimenttransport rate and sand flow structure of Tamarix nebkhas had been systematicallystudied so as to further understand land degradation causes and processes of oasis-deserttransition zone, and provide theoretical basis for oasis security and nebkhasconservation. The results showed that:(1) The three-dimensional airflow structure of Tamarix ramosissima nebkhas canbe divided into six regions: the deceleration zone before nebkhas, the accelerationregion of nebkhas windward, the high speed zone on both sides of nebkhas, the strongvortex area on leeward side of nebkhas, the recovery zone after nebkhas and the mixedacceleration zone above nebkhas. The influence region of nebkhas on airflow patternswas -10H~14H in horizontal direction and width of side influence zone was less than3/4 of nebkhas width. In vertical direction, the airflow patterns were significantlyaffected by nebkhas height, the maximum influence height was less than 2H. Thebackground vegetation coverage played an important role in affecting the airflowpatterns. With increase of background vegetation coverage, the deceleration zone atfront of nebkhas and recovery zone behind nebkhas were expanded, meanwhile thestrong vortex zone on lee side and high speed zone at both sides of nebkhas shrinked.The wind velocity was significantly reduced at the layer where the backgroundvegetation existed. The airflow acceleration rate at each region of nebkhas showed anearly exponential decay with background vegetation coverage. When the coverage ismore than 16% the acceleration rate tended to be steady.(2) With increase of background vegetation coverage from 0%, to 4%, to 10% , to16% and to 26%, the threshold wind velocity of sand-driving on interdune was 4.4 m·s-1, 5.4 m·s-1, 5.8 m·s-16.2 m·s-1and 7.2 m·s-1respectively, while on nebkhas they were3.2 m / s, 4.4 m·s-1, 5.0 m·s-1, 5.2 m·s-1, 5.4 m·s-1respectively. The threshold wind speedat interdune is about 1 m·s-1higher than that on nebkhas surface, which suggest thatnebkhas surface is more prone to wind erosion than the interdune. Tamarix ramosissimanebkhas and interdune can be divided into six regions. They are named theaccumulation area before nebkhas, the erosion area on windward slope of nebkhas, theerosion area on both sides of the nebkhas, the vortex flow sediment area on leewardside of nebkhas, the wake accumulation area after nebkhas and the no affected area,respectively. Both wind velocity and background vegetation coverage played animportant role in affecting the erosion distribution. With increase of wind velocity,the accumulation area before nebkhas and the wake accumulation area after nebkhasare narrowed, while the erosion area on both sides of the nebkhas are expandedsignificantly. The erosion area ratio, erosion intensity and wind erosion rate at nebkhasand interdune decreased exponentially with increase of background vegetationcoverage. When the vegetation coverage is low the influence of wind velocity on theerosion intensity is obvious. The nebkhas on the bare sand can aggravate wind erosion,but nebkhas can block sand flow even sparse vegetation existing on the interdune.(3) The surface aerodynamic parameters were significantly correlated with thebackground vegetation coverage. With the increase of vegetation coverage, theaerodynamic roughness length (z0) and the drag coefficient (cd) increased exponentially,the friction wind speed (u*) increased logarithmically, while the sediment transport fluxdecreases exponentially. There was a significant correlation between surfaceaerodynamic parameters and the sediment transport flux. The sediment transport fluxdecreased exponentially with the increasing of roughness length (z0), friction windspeed (u*) and drag coefficient (cd).(4) Based on the analysis of the correlation of the acceleration rate, the winderosion rate, the sediment transport flux and the background vegetation coverage, it was found that there was a good correlation between the acceleration and erosion intensityof nebkhas. The total wind erosion rate and sediment transport flux on Tamarix shruband its interdune showed exponentially law with background vegetation coverage, thechange was not obvious when the vegetation coverage was>16%. It is inferred that themaintenance of no less than 16% of the background vegetation cover should be theprerequisite for scientific conservation of nebkhas in oasis-desert ecotone.
语种	中文
学科主题	环境工程
内容类型	学位论文
源URL	[http://ir.xjlas.org/handle/365004/14897]
专题	新疆生态与地理研究所_研究系统_荒漠环境研究室
作者单位	中国科学院新疆生态与地理研究所
推荐引用方式 GB/T 7714	谭凤翥. 柽柳灌丛沙堆风沙动力学过程的风洞实验[D]. 新疆乌鲁木齐. 中国科学院大学. 2017.

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