Wind-induced Tree Vibration Simulation On Different Canopy Structure

Trees are the basic elements of natural resources of the earth's surface,it prevent solid earth,play multiple role in greening the city.Typhoon and other extreme weather easily broken tree branches and lodging even uprooted trees damage phenomenon,caused great impact for forest production and operation,the residents' lives and property.Different tree species performance difference wind resistance,Chinese fir are widely planted in southern China,such as fujian,guangxi,etc.as subtropical economic forest tree species,it has a wide range of uses such as bridges,buildings,furniture,etc.This article,for Chinese fir,adopting finite element numerical calculation method of fir branches system structure characteristics and the characteristics of wind-induced dynamic response study,summarize the law of the wind vibration characteristics analysis of fir structure.In addition,on the basis of wind vibration analysis,judgement and identification while wind-induced leaf litter,and simulated the leaf litter 3D visualization process,so as to provide reference for forestry production and tree pruning.This article mainly includes three aspects of research work:(1)Simplify individual fir entity modeling;the geometrical model of trees is the foundation of the wind vibration analysis.The traditional method of tree modeling focused on the expression of authenticity,and cannot be used for tree structural mechanics analysis.Therefore,this article adopts the method of 3D entity modeling,and according to the geometry characteristics of Chinese fir,simplifying the fir branches to variable cross-section of the cone to simplify modeling.Then,using parametric modeling to adapt to different trees morphological structure characteristics of fast and effective modeling,and construction:a full Chinese fir model,10 different canopy pruning model(including two different branches length,three different position of canopy,five different distribution of branches).(2)Chinese fir structure natural vibration characteristics and wind vibration response analysis;due to relatively complicated structural vibration characteristics of trees,this paper tries to build model of multiple sets of Chinese fir from multiple perspectives and various factors influencing the performance of Chinese fir vibration(canopy sparse degree,branch length,distribution of canopy and position,canopy branches).The experimental results show that:1)Leaves of Chinese fir vibration influence is mainly decided by the viscous damping coefficient of canopy of leaves,canopy leaf distribution density is more dense,the greater the effect on the vibration of the fir leaves,and its vibration frequency range is smaller;2)Tree branches of length to diameter ratio is one of the important structure parameters affect vibration;3)the vibration of the fir is mainly for bending vibration and torsional vibration,of which the trunk is given priority to with bending vibration,with local torsional vibration is complementary,and branches of bending and torsional vibration may also be affected.4)canopy position change has significant effect for the natural vibration characteristics of trees,under the canopy of trees distribution,the smaller the natural vibration frequency range of the trees;5)the trunk and branches of geometry is the important factors that affect trees change local vibration(length,radius and length to diameter ratio),the canopy of trees form is the key factors that lead to changes in overall vibration characteristics trees(height,thickness,crown width,sparse degree).(3)The wind-induced movements and the 3D visualization simulation of the litter leaves;on the basis of wind vibration analysis,futher analysis is the features of leaf motion,leaves wind-induced motion can be divided into branches with sports and leaves two parts,respectively to hang the leaves and litter leaves to simplify the motion simulation.In addition,incentive effect caused by the wind fallen leaves a quick judgment,recognition of leaf litter,when the leaves fall occurred,use path synthesis can realize the fast simulation of falling balls,and according to the physiological characteristics of the fallen leaves and phenological changes rhythms,so as to realize the dynamic simulation of deciduous quantity changes with the seasons.