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Lanzhou University (2021)

Numerical Modelling of Windbreak Effect and Mechanism of Shelterbelts

崔双伟

Titre : Numerical Modelling of Windbreak Effect and Mechanism of Shelterbelts

Auteur : 崔双伟

Grade : Master 2021

Université : Lanzhou University

Résumé
The sandstorm disaster in Northwest China is very serious,which greatly affects People’s Daily production and life.The windbreak forest belt has the effect of windbreak and sand blocking,slowing down the movement speed of dunes and effectively protecting the highway and railway lines in the desert,so it is widely used in practical projects.In order to study the shelter belt in different spacing and different porosity under the condition of windbreak and sand resistance,this article uses the ANSYS Fluent software to numerical simulation of shelter belt,through the use of porous jump boundary condition instead of actual shelter belt 7 row shelter belt are studied in the space between three and four kinds of porosity of flow field velocity distribution characteristics,the grains of sand movement and the accumulation,the formation of the forest,the effective protection area and the forest change law of pressure difference before and after the power and ground friction shelter belt optimal parameters provide reference data for engineering design.The main research results of this paper include the following aspects :(1)Calculate the streamline distribution characteristics of the 7 rows of protection forest belts in the two dimensions calculation domain and the airflow velocity distribution characteristics at height when the forest belt porosity is 20%,30%,40%,and 50% when the protection forest belt spacing is 5h,10 h and 15 h.The analysis of the results indicates that the windbreak forest belt has a better protective effect when the forest belt spacing is 30%.(2)On the basis of(1),numerical calculation of the movement trajectory of sand particles passing through the windbreak forest belt under the four porosity conditions when the distance between the windbreak forest belts is set 10 h,the characteristics of the movement of sand particles near the forest belts are obtained,and the accumulation and distribution of sand particles are obtained through analysis.From the sand movement accumulation,the sand blocking effect of the windbreak forest belt is studied.(3)Three-dimensional numerical simulation of windbreak forest belts was carried out,and the effective protection area formed by windbreak forest belts under three forest belt spacings and four porosity conditions was studied.By analyzing the distribution form and numerical value of the effective protection area,it is considered that it is purely from the perspective of the effective protection area Considering that,the protection effect is better when the forest zone spacing is 20% of the forest zone porosity.However,if the effect of reflow is considered,30% porosity is considered better.(4)On the basis of(3),the variation law of the pressure difference force and ground friction force of the windbreak forest belt with porosity is studied for the working condition of the forest belt spacing.

Mots clés : Windbreak ;Porous media model ;Forest belt spacing ;Porosity;Lagrangian particle tracking method ;

Présentation (CNKI)

Page publiée le 17 novembre 2021