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Central University for Nationalities (2005)

The semiarid northern Aeolian Activities and vegetation conditions coupled relationship

Shi Xue Feng

Titre : The semiarid northern Aeolian Activities and vegetation conditions coupled relationship

Auteur : Shi Xue Feng

Grade : Master 2005

Université : Central University for Nationalities

Résumé
Semiarid area of ??northern China are mainly distributed east of Inner Mongolian Plateau and the Loess Plateau, its unique natural conditions and ecological systems constitute an important ecological barrier in northern China. Hebei and Inner Mongolia border, is located in semi-arid zones typical Ecotone, changing land use patterns, vegetation conditions and Aeolian Activities Coupling relationship between the region vegetation recovery in this region and around Beijing and Tianjin, the regional ecological environment improve the delivery of important theoretical support. To study the mechanism of vegetation conditions and Aeolian Activities, built their own wind tunnel of the indoor environment. The construction of the indoor environment wind tunnel total length of 13.3m, fan connection section, rectifier segment, stable segment, test section, diffuser section and dust segment, in which the test section of 2.3m, the cross-section of 50cm square, wind speed wind tunnel by 0 20m / s continuous adjustable. Wind tunnel test results show that the environmental wind tunnel to meet the requirements of similarity theory, the general theory of the nature of the atmospheric boundary layer, so you can wind tunnel experiments. Sand activities under natural conditions in the wind tunnel simulation, different vegetation conditions (height, line spacing, plant spacing, coverage, silhouette cover) for wind speed, wind profile, the underlying surface aerodynamic parameters, sand starter wind speed, wind erosion, sediment transport rate and its vertical distribution experiment and find out by analyzing the correlation between changes in the law, is derived on the basis of the the vegetation impact under the conditions of the sediment transport rate model. By to contrast vegetation and vegetation near-surface wind speed distribution, the presence of vegetation change airflow distribution of near-surface wind profile with height no longer follows the logarithmic law, but the sector is divided into two layers of vegetation height : lower for rough sub-layer, the upper inertial sub-layer. Study of the effect of vegetation conditions wind, the wind speed decreases exponentially increasing trend with vegetation silhouette cover, exponentially decreasing trend with the vegetation model plant spacing and line spacing and plant spacing greater than the line spacing of the wind speed. Land surface aerodynamic roughness is a physical quantity to measure the extent of the underlying surface bumps land surface aerodynamic roughness with vegetation silhouette cover change to meet the exponential function fitting equation : Z A, b, exP (c, · Sichuan, vegetation scattered arrangement of its land surface aerodynamic roughness higher than coincidence arrangement vegetation. This paper summarizes has sediment transport rate model based on, introducing vegetation cover K Vegetation silhouette corpse and vegetation cover arranged coefficient A as a parameter to describe vegetation conditions through theoretical analysis and experimental analysis of sediment transport rate under the conditions of the vegetation cover model :

Mots clés : Wind tunnel experiments Vegetation conditions Roughness Sediment transport rate

Présentation (Dissertation topics)

Page publiée le 12 octobre 2014, mise à jour le 10 octobre 2017