The Numerical Simulation Of Flow Fields On The Trees By Lattice Boltzmann Method

The damage caused by wind disasters occurred frequently.whether it is typhoon in the coastal area or the strong wind disasters in inland areas,all has a great impact on the stability of the forest ecosystem.Meanwhile,the trees are prone to breaking and lodging under the action of strong wind,which makes the pedestrians ' life and property security seriously threatened.Therefore,it is important to study the wind field of trees.Lattice Boltzmann method(LBM)is an efficient numerical simulation method based on computational fluid dynamics.This method is used to simulate the flow field of a simplified tree model in this paper.Firstly,the two-dimensional solid square column and the porous square cylinder are simulated by LBM in the format of multiple relaxation times.The results of several typical Reynolds numbers are described.Additionally,in order to confirm the feasibility and the correctness of LBM,the typical parameters are also analyzed in detail and compared with data in other literatures.Secondly,the flow field of a two-dimensional vertical tree is studied numerically by LBM in the format of multiple relaxation times,The tree is simplified to porous medias at scale of representative elementary volume.In order to study the tree flow field under high Reynolds number,the large eddy simulation is introduced into LBM to obtain the wind velocities and pressures around the canopy.Additionally,the results are compared with the measured data of predecessors,it is proved that the LBM simulation on the flow field of a tree is accurate and feasible.Then the grids are set in front of the model,which makes the disturbance and simulates the flow field of a tree under the B type site.And the variations of the wind speed and turbulence intensity are expounded emphatically under the B type site.The LBM algorithm has the advantages of high parallelism,fast solution speed and reliable calculation results,which is expected to be an efficient numerical simulation method for solving practical problems such as the wind field of trees.Finally,based on the above research,using the same simulation method,the flow field of a two-dimensional tree in a plane is simulated by the C + + program.Firstly,the velocities in the flow field of a single tree are verified numerically,which proves the accuracy of LBM programs and the rationality of modeling applications.And then what influences the variations of the model aspect ratio have on the wind velocities behind the canopy and wind pressures in the flow field is studied.Secondly,the flow fields of many tree models are simulated,and the influence of different cropping modes on the wind-blown performance of trees is analyzed.