Modeling of Surface Roughness for Flow over a Complex Vegetated Surface

Authors: Wichai Pattanapol, Sarah J. Wakes, Michael J. Hilton, Katharine J.M. Dickinson

Abstract:

Turbulence modeling of large-scale flow over a vegetated surface is complex. Such problems involve large scale computational domains, while the characteristics of flow near the surface are also involved. In modeling large scale flow, surface roughness including vegetation is generally taken into account by mean of roughness parameters in the modified law of the wall. However, the turbulence structure within the canopy region cannot be captured with this method, another method which applies source/sink terms to model plant drag can be used. These models have been developed and tested intensively but with a simple surface geometry. This paper aims to compare the use of roughness parameter, and additional source/sink terms in modeling the effect of plant drag on wind flow over a complex vegetated surface. The RNG k-ε turbulence model with the non-equilibrium wall function was tested with both cases. In addition, the k-ω turbulence model, which is claimed to be computationally stable, was also investigated with the source/sink terms. All numerical results were compared to the experimental results obtained at the study site Mason Bay, Stewart Island, New Zealand. In the near-surface region, it is found that the results obtained by using the source/sink term are more accurate than those using roughness parameters. The k-ω turbulence model with source/sink term is more appropriate as it is more accurate and more computationally stable than the RNG k-ε turbulence model. At higher region, there is no significant difference amongst the results obtained from all simulations.

Keywords: CFD, canopy flow, surface roughness, turbulence models.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1058657

References:

[1] Finnigan, J.J., "Turbulence in plant canopies," Annu Rev Fluid Mech, 2000. 32: p. 519-571.
[2] Lancaster, N. and A. Bass, "Influence of vegetation cover on sand transport by wind: Field studies at Owens Lake, California," Earth surf. process. landforms, 1998. 23: p. 69-82.
[3] Putten, W.H.V.D., "Establishment of Ammophilla Arenaria ( Marram Grass) From Culms, Seeds and Rhizomes," The Journal of Applied Ecology, 1990. 27: p. 188-199.
[4] Mohan, M. and M.K. Tiwari, "Study of momentum transfers within a vegetation canopy," Proc. Indian Acad. Sci. (Earth Planet. Sci.), 2004. 113: p. 67-72.
[5] Poggi, D., G.G. Katul, and J.D. Albertson, "Momentum transfer and turbulent kinetic energy budgets within a dense model canopy," Boundary-Layer Meteorology, 2004. 111: p. 589-614.
[6] Kim, H.G., V.C. Patel, and C.M. Lee, "Numerical simulation of wind flow over hilly terrain," Journal of wind engineering and industrial aerodynamics, 2000. 87: p. 45-60.
[7] Lun, Y.F., et al., "Applicability of linear type revised k ╬Á models to flow over topographic features," Journal of wind engineering and industrial aerodynamics, 2007. 95: p. 371-384.
[8] Maurizi, A., J.M.L.M. Palma, and F.A. Castro, "Numerical simulation of the atmospheric flow in a mountainous region of the North of Partugal," Journal of wind engineering and industrial aerodynamics, 1998. 74-76: p. 219-228.
[9] Ayotte, K.W., J.J. Finnigan, and M.R. Raupach, "A second-order closure for neutrally stratified vegetative canopy flows," Boundary- Layer Meteorol, 1999. 90: p. 189-216.
[10] Green, S.R., "Modelling turbulent air flow in a stand of widelyspaced trees," Phoenics J., 1992. 5(294-312).
[11] Katul, G.G., et al., "One- and Two-equation models for canopy turbulence," Boundary-Layer Meteorol, 2004. 113(80-109).
[12] Neary, V.S., "Numerical solution of fully developed flow," Journal of engineering mechanics, 2003. 129: p. 558-563.
[13] Sogachev, A. and O. Panferov, "Modification of two-equation models to account for plant drag," Boundary-Layer Meteorol, 2006. 121: p. 229-266.
[14] Sherman, D.J., et al., "Wind-blown sand on beaches: an evaluation of models," Geomorphology, 1998. 22: p. 113-133.
[15] Stephen, M. and Z. Xin, "Computational analysis of pressure and wake characteristics of an aerofoil in ground effect," Journal of fluid engineering, 2005. 127: p. 290-298.
[16] Launder, B.E. and D.B. Spalding, "The numerical computational of turbulent flows," Computer methods in applied mechanics and engineering, 1974. 3: p. 269-289.
[17] Yakhot, V. and S.A. Orszag, "Renormalization group analysis of turbulence: I. Basic theory," Journal of Scientific Computing, 1986. 1(1): p. 1-51.
[18] Shih, T.-H., et al., "A New k-╬Á eddy-viscosity model for high Reynolds number turbulent flows model development and validation," Computers fluids, 1995. 24(3): p. 227-238.
[19] Menter, F.R., "Two-equation eddy-viscosity turbulence models for engineering applications," AIAA Journal, 1994. 32(8): p. 1598-1605.
[20] Wakes, S.J., et al., "Using Computational Fluid Dynamics to investigate the effect of a Marram covered foredune; initial results," in Seventh International Conference on Modelling, Measurements, Engineering and Management of Seas and Coastal Regions. 2005: Algarve, Portugal.
[21] Li Liang, et al., "Improved k-╬Á two-equation turbulence model for canopy flow," Atmospheric Environment 2006. 40: p. 762-770.
[22] Aynsley, R.M., W. Melbourne, and B.J. Vickery, "Architectural Aerodynamics," 1977: Applied Science.
[23] Raupach, M.R. and R.H. Shaw, "Averaging procedures for flow within vegetation canopies," Boundary-Layer Meteorol, 1982. 22: p. 79-90.
[24] Sanz, C., "A note on k − ╬Á modelling of vegetation canopy airflows," Boundary-Layer Meteorology, 2003. 108: p. 191-197.
[25] Foudhil, H., Y. Brunet, and J.-P. Caltagirone, "A fine-scale k-╬Á model for atmospheric flow over heterogeneous landscapes," Environ Fluid Mech, 2005. 5: p. 247-265.
[26] Liu, J., et al., "E-╬Á modelling of turbulent air flow downwind of a model forest edge," Boundary-Layer Meteorol 1996. 77: p. 21-44
[27] Blocken, B., T. Stathopoulos, and J. Carmeliet, "CFD simulation of the atmospheric boundary layer: wall function problems," Atmospheric environment 2007. 41: p. 238-252.
[28] Parsons, D.R., et al., "Numerical of airflow over an idealised transverse dune," Environmental modeling and software, 2004. 19: p. 153-162.
[29] Neff, D.V. and R.N. Meroney, "Wind-tunnel modeling of hill and vegetation influence on wind power availability," Journal of wind engineering and industrial aerodynamics, 1998. 74-76: p. 335-343.
[30] Cao, S. and T. Tamura, "Experimental study on roughness effects on turbulent boundary layer flow over a two-dimensional steep hill," Journal of wind engineering and industrial aerodynamics, 2006. 94: p. 1-19.