Influence Of Forest Stand Parameters On Windbreak Variables Using A Fluid Simulation Technique

With the frequent occurrence of strong wind disasters,the damage to forests as a natural barrier against wind disasters is increasing.The damage caused the leaves are largely detached,the branches are broken,and the roots are uprooted,at worst,forest large areas are lodging,causing losses to the national economy,and it is even likely to threaten people’s lives.Therefore,it is extremely urgent for current researchers to study the distribution characteristics of internal flow field under strong wind loads.the analysis of wind distribution characteristics not only provides a theoretical basis for tree safety assessment,and also provides a basis for windbreak planting.The main research and conclusions on tree safety assessment as follows:1.Taking the crown shape as the research object,the forest model is established using porous media crown.It is assumed that the fluid in the forest stand is a uniform fluid under wind load,and the fluid-solid coupling motion is transformed into a solid phase and a fluid phase by using the Euler two-phase flow model,and obtained the fluid motion control equation.Then,the model calculation area is discretized,by iteratively calculating the wind parameters in each grid,the relationship between the crown shape and the tree safety is obtained,our results are compared with the results in the literature to verify the conclusion.Through numerical simulation and literature verification,the difference of pressure,velocity before and after the conical tree crown is smaller than others,and turbulence intensity of conical crown is the smallest at three shapes,therefore,the conical crown features are safer under strong wind load.2.For the field scanning of radar,two tree species(PR107,CATAS7-20-59)spatial point cloud data were obtained to reconstruct the tree skeleton,and the foliage clump volume,leaf area index,porosity,and foliage clumps were obtained by leaf attribution.Then the foliage clump forest stand model of the two tree species is established,and each foliage clump in the canopy is simulated with a porous media.After simulating the tree model under strong wind,it is found that the dynamic pressure in the forest stand 1 composed of the rubber tree 1 is generally higher than that in the rubber tree 2,the wind speed change and the turbulent energy intensity change in the forest are also larger than the forest stand 2.These factors these will cause the instability of local cyclones and the increase of turbulence intensity in the forest stand 1,so that the wind damage to the rubber tree 1(PR107)is greater than that of the rubber tree 2(CATAS7-20-59).This is consistent with the damaged situation of the tree species in the field.3.Taking the crown parameter-porosity as the research object,the single-plant and multi-plant models were established respectively,and the model was numerically simulated according to the standard turbulence ?-ε model.According to the simulation results,it showed that the crown porosity was larger,the smaller the pressure difference before and after the crown,the smaller the wind speed difference in the canopy,and it is not easy to occur turbulence,therefore the sparse crown tree is more safety.