Wind and Structures

Techno-Press (테크노프레스)
권호 표지
DOI QR코드

DOI QR Code

Effect of trunk length on the flow around a fir tree

  • Lee, Jin-Pyung (School of Environmental Science and Engineering, Pohang University of Science and Technology) ;
  • Lee, Eui-Jae (Department of Mechanical Engineering, Pohang University of Science and Technology) ;
  • Lee, Sang-Joon (Department of Mechanical Engineering, Pohang University of Science and Technology)
  • Received : 2012.12.07
  • Accepted : 2013.09.24
  • Published : 2014.01.25
⟨ Previous Next ⟩

Abstract

Flow around a small white fir tree was investigated with varying the length of the bottom trunk (hereafter referred to as bottom gap). The velocity fields around the tree, which was placed in a closed-type wind tunnel test section, were quantitatively measured using particle image velocimetry (PIV) technique. Three different flow regions are observed behind the tree due to the bottom gap effect. Each flow region exhibits a different flow structure as a function of the bottom gap ratio. Depending on the gap ratio, the aerodynamic porosity of the tree changes and the different turbulence structure is induced. As the gap ratio increases, the maximum turbulence intensity is increased as well. However, the location of the local maximum turbulence intensity is nearly invariant. These changes in the flow and turbulence structures around a tree due to the bottom gap variation significantly affect the shelter effect of the tree. The wind-speed reduction is increased and the height of the maximum wind-speed reduction is decreased, as the gap ratio decreases.

Keywords

Acknowledgement

Supported by : National Research Foundation of Korea(NRF)

References

  1. Bitog, J.P., Lee, I.B., Shin, M.H., Hong, S.W., Hwang, H.S., Seo, I.H., Yoo, J.I., Kwon, K.S., Kim, Y.H and Han, J.W. (2009), "Numerical simulation of an array of fences in Saemangeum reclaimed land", Atmos. Environ., 43(30), 4612-4621. https://doi.org/10.1016/j.atmosenv.2009.05.050
  2. Bourdin, P. and Wilson, J.D. (2008), "Windbreak aerodynamics: is computational fluid dynamics reliable?", Bound.- Lay. Meteorol., 126(2),181-208. https://doi.org/10.1007/s10546-007-9229-y
  3. Castro, I.P. (1971), "Wake characteristics of two-dimensional perforated plates normal to an airstream", J. Fluid Mech., 46, 599-609. https://doi.org/10.1017/S0022112071000727
  4. Cleugh, H.A. (1998), "Effects of windbreaks on airflow, microclimates and crop yields", Agroforest. Syst., 41(1), 55-84. https://doi.org/10.1023/A:1006019805109
  5. Gross, G. (1987), "A numerical study of the air flow within and around a single tree", Bound.- Lay. Meteorol., 40(4), 311-327. https://doi.org/10.1007/BF00116099
  6. Guan, D., Zhang, Y. and Zhu, T. (2003), "A wind-tunnel study of windbreak drag", Agr. Forest. Meteorol., 118(1-2), 75-84. https://doi.org/10.1016/S0168-1923(03)00069-8
  7. Chen, G., Wang, D., Sun, C. and Li, J. (2012), "3D numerical simulation of wind flow behind a new porous fence", Powder Technol., 230, 118-126. https://doi.org/10.1016/j.powtec.2012.07.017
  8. Hagen, J.L., Skidmore, E.L., Miller, P.L. and Kipp, J.E. (1981), "Simulation of effect of wind barriers on airflow", Trans - ASAE 24, 1002-1008. https://doi.org/10.13031/2013.34381
  9. Heisler, G.M. and Dewalle, D.R. (1988), "Effects of windbreak structure on wind flow", Agr. Ecosyst. Environ., 22, 41-69.
  10. Judd, M.J., Raupach, M.R. and Finnigan, J.J. (1996), "A wind tunnel study of turbulent flow around single and multiple windbreaks, part I: Velocity fields", Bound.- Lay. Meteorol., 80(1-2), 127-165 https://doi.org/10.1007/BF00119015
  11. Kim, H.B. and Lee, S.J. (2002), "The structure of turbulent shear flow around a two-dimensional porous fence having a bottom gap", J. Fluid. Struct., 16(3), 317-329. https://doi.org/10.1006/jfls.2001.0423
  12. Melese, E.A., Hertog, M., Delele, M.A., Baetens, K., Persoons, T., Baelmans, M., Ramon, H., Nicolai, B.M. and Verboven, P. (2009) "CFD modelling and wind tunnel validation of airflow through plant canopies using 3D canopy architecture", Int. J. Heat Fluid Fl., 30(2), 356-368. https://doi.org/10.1016/j.ijheatfluidflow.2008.12.007
  13. Perera, M.D.A.S. (1981), "Shelter behind two-dimensional solid and porous fences", J. Wind Eng. Ind. Aerod., 8(1-2), 93-104. https://doi.org/10.1016/0167-6105(81)90010-6
  14. Raine, J.K. and Stevenson, D.C. (1977), "Wind protection by model fences in a simulated atmospheric boundary layer", J. Wind Eng. Ind. Aerod., 2(2), 17-39.
  15. Rosendfeld, M., Marom, G. and Bitan, A. (2010), "Numerical simulation of the airflow across trees in a windbreak", Bound. - Lay. Meteorol., 135(1), 89-107. https://doi.org/10.1007/s10546-009-9461-8
  16. Torita, H. and Satou, H. (2007), "Relationship between shelterbelt structure and mean wind reduction", Agr. Forest. Meteorol., 145(3-4), 186-194. https://doi.org/10.1016/j.agrformet.2007.04.018
  17. van Eimern, J., Karschon, R., Razumova, L.A. and Robertson, G.W. (1964), Windbreaks and Shelterbelts, W.M.O. Tech. Note No. 59.
  18. Wang, H., Takle, E.S. and Shen, J. (2001) "Shelterbelts and windbreaks: mathematical modeling and computer simulations of turbulent flows", Annu. Rev. Fluid Mech., 33, 549-586. https://doi.org/10.1146/annurev.fluid.33.1.549

Cited by

  1. Experimental study for wind pressure loss rate through exterior venetian blind in cross ventilation vol.107, 2015, https://doi.org/10.1016/j.enbuild.2015.08.018
  2. Nonlinear dynamics and failure wind velocity analysis of urban trees vol.22, pp.1, 2016, https://doi.org/10.12989/was.2016.22.1.089