Environmental Fluid Mechanics

, Volume 12, Issue 1, pp 23–44 | Cite as

A CFD study of wind patterns over a desert dune and the effect on seed dispersion

  • Eugéne C. Joubert
  • Thomas M. Harms
  • Annethea Muller
  • Martin Hipondoka
  • Joh R. Henschel
Original Article

Abstract

In the Namib Desert seed distribution is greatly influenced by wind patterns. Existing literature regarding wind patterns over dunes focuses on two-dimensional simulations of flow over simplified dune structures. The three-dimensional geometries of the sand dunes suggests far more complex flow features exist, which are not captured by two-dimensional simulations. Computational fluid dynamics (CFD) was used to reproduce the three-dimensional near surface wind patterns around a dune with the aim to learn more about seed distribution. Field work included terrain mapping, wind speed, direction and temperature metering. The CFD results show the expected two-dimensional flow features of high pressure at the dune toe, low pressure at the crest and flow acceleration up windward slope. Also observed are some three-dimensional flow features such as a spiral vortex near the crest and transverse flow due to crest-line curvature of the dune. It was also observed how the wall shear stress differs due to the three-dimensional shape of the dune. The wall shear stress suggests that seed accumulation is more likely to occur behind trailing (down-wind) crest edges. Particle tracking showed how seeds tend to move over the dune crest and recirculate towards the crest on the lee-side. The study showed that adding the third dimension makes the simulations more complex, adds to computational requirements and increases simulation time but also provides vital flow information which is not possible with two-dimensional simulations.

Keywords

Computational fluid dynamics Atmospheric flow Dune Particle tracking 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Parsons D et al (2004) Numerical modelling of flow over an idealised transverse dune. Environ Model Softw 19: 153–162CrossRefGoogle Scholar
  2. 2.
    Parsons D et al (2004) Numerical modelling of flow structures over idealised transverse aeolian dunes of varying geometry. Geomorphology 59: 149–164CrossRefGoogle Scholar
  3. 3.
    Wiggs GFS, Livingstone I, Warren A (1996) The role of streamline curvature in sand dune dynamics: evidence from the field and wind tunnel measurements. Geomorphology 17: 29–46CrossRefGoogle Scholar
  4. 4.
    Tsoar H (1978) The dynamics of longitudinal dunes: final technical report. European Research Office, U.S. Army, London, DA-ERO 76-G-072Google Scholar
  5. 5.
    Livingstone I (1985) The dynamics of sand transport on a Namib linear dune. PhD Thesis, Hertford College, University of Oxford, EnglandGoogle Scholar
  6. 6.
    Joubert EC (2010) A computational fluid dynamic study of the near surface wind patterns over a desert dune and the effect on seed dispersion. MScEng Thesis, Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, South AfricaGoogle Scholar
  7. 7.
    De Villiers E (2006) The potential of large eddy simulation for the modeling of wall bounded flows. PhD Thesis, Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, LondonGoogle Scholar
  8. 8.
    Ferziger JH, Perić M (1996) Computational methods for fluid dynamics. Springer, BerlinGoogle Scholar
  9. 9.
    Muller AA (2009) The dynamics of seed bank dispersal and deposition under natural environmental conditions in the central Namib and Kalahari Desert. MSc Thesis, Department of Environmental and Geographical Science, University of Namibia, NamibiaGoogle Scholar
  10. 10.
    Combrinck ML (2008) A computational fluid dynamic analysis of the air flow over the keystone plant species, Azorella Selago, on Sub-Antarctic Marion Island. MScEng Thesis, Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, South AfricaGoogle Scholar
  11. 11.
    Flemmer RLC, Banks CL (1986) On the drag coefficient of a sphere. Power Technol 48: 217–221CrossRefGoogle Scholar
  12. 12.
    Versteeg HK, Malalasekera W (2007) An introduction to computational fluid dynamics: the finite volume method, 2nd edn. Pearson Prentice Hall, London, EnglandGoogle Scholar
  13. 13.
    Jasak H, Weller HG, Gosman AD (1999) High resolution NVD differencing scheme for arbitrarily unstructured meshes. Int J Numer Methods Fluids 31: 431–449CrossRefGoogle Scholar
  14. 14.
    Launder BE, Spalding DB (1974) The numerical computation of turbulent flows. Comput Methods Appl Mech Eng 3: 269–289CrossRefGoogle Scholar
  15. 15.
    Kim S, Boysan F (1999) Application of CFD to environmental flows. J Wind Eng Indus Aerodyn 81: 145–158CrossRefGoogle Scholar
  16. 16.
    Lee S (1997) Unsteady aerodynamic force prediction on a square cylinder using \({k-\varepsilon}\) turbulence models. J Wind Eng Indus Aerodyn 67–68: 79–90CrossRefGoogle Scholar
  17. 17.
    Rodi W (1997) Comparison of LES and RANS calculations of the flow around bluff bodies. J Wind Eng Indus Aerodyn 69–71: 55–75CrossRefGoogle Scholar
  18. 18.
    Lübcke H, Schmidt St, Rung T, Thiele (2001) Comparison of LES and RANS in bluff-body flows. J Wind Eng Indus Aerodyn 89: 1471–1485CrossRefGoogle Scholar
  19. 19.
    Patankar SV, Spalding DB (1972) A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows. International Journal of Heat and Mass Transfer, 15Google Scholar
  20. 20.
    Richards PJ (1989) Computational modelling of wind around a low rise building using PHOENIX. Report for the ARFC Institute of Engineering Research West Park, Silsoe Research Institute, Bedfordshire, UKGoogle Scholar
  21. 21.
    Richards PJ, Hoxey RP (1993) Appropriate boundary conditions for computational wind engineering models using the \({k-{\varepsilon}}\) turbulence model. J Wind Eng Indus Aerodyn 46 and 47: 145–153CrossRefGoogle Scholar
  22. 22.
    Blocken B, Stathopoulos T, Carmeliet J (2007) CFD simulation of the atmospheric boundary layer: wall function problems. Atmospher Environ 41(2): 238–252CrossRefGoogle Scholar
  23. 23.
    Joubert GE (2011) Flow analysis of the hull-keel joint fairing on sailboats. BEng Final Year Project, Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, South AfricaGoogle Scholar
  24. 24.
    Driver DM, Seegmiller HL (1985) Features of a reattaching turbulent shear layer in divergent channel flow. AIAA J NASA Ames Res Center Moffet Field CA 23(2): 163–171Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Eugéne C. Joubert
    • 1
  • Thomas M. Harms
    • 1
  • Annethea Muller
    • 2
  • Martin Hipondoka
    • 2
  • Joh R. Henschel
    • 3
  1. 1.Department of Mechanical and Mechatronic EngineeringStellenbosch UniversityStellenboschSouth Africa
  2. 2.Environmental and Geographic DepartmentUniversity of NamibiaWindhoekNamibia
  3. 3.Gobabeb Training and Research CentreDesert Research Foundation of NamibiaWindhoekNamibia

Personalised recommendations