JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2019, Vol. 43 ›› Issue (02): 107-113.doi: 10.3969/j.issn.1000-2006.201804035

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Influence of forest canopy shape on windbreak variables using a fluid simulation technique

HUANG Xiao1, YUN Ting1*, XUE Lianfeng1, HU Chunhua1, CHEN Bangqian2   

  1. (1.College of Information Science and Technology, Nanjing Forestry University, Nanjing 210037,China; 2.Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou 571737, China)
  • Online:2019-03-30 Published:2019-03-30

Abstract: 【Objective】 Studying the distribution of wind fields inside forests with different canopy shapes under strong wind disturbance can provide a theoretical basis for the selection of tree species in windbreak forest construction and planting.【Method】 First, we established three different forest models with different canopy shapes, in which the canopy structure was simulated using porous media. The relationship between the porosity of the medium and the leaf area index(LAI)was determined from the extinction coefficient of the corresponding tree species. Then, based on the k-ε equation turbulence model, we added source terms into the momentum equation to calculate wind velocity, pressure, and turbulent energy intensity of different canopy shapes under strong wind loads.【Result】The difference between the minimum wind speed in the conical canopy forest(0.047 m/s)and the minimum wind speed in the truncated-conical canopy forest(0.076 m/s)was 0.029 m/s. The minimum wind speed in the ellipsoidal canopy was 0.940 m/s, and the fluctuation was greater than for other crowns. The conical canopy forest had the lowest difference in pressure(30.22 Pa)and turbulent kinetic energy(0.17%). The pressure difference in the ellipsoidal canopy forest was the largest(mean: 62.14 Pa). Turbulence intensity in the truncated-conical canopy forest was the largest, with a maximum of 25.19%.【Conclusion】The method proposed in this paper solved the problem that wind factors such as turbulent kinetic energy intensity and differential pressure at real time cannot obtain due to the complexity of the tree canopy. Because of the influence of turbulent energy intensity on the wind-resistant safety of trees and the reduction of wind speed and pressure difference, crowns with characteristics similar to the conical canopy should be selected when constructing a wind-proof forest system.

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