Turbulent flow in canopies on complex topography and the effects of stable stratification
- Cite this paper as:
- Finnigan J. (2007) Turbulent flow in canopies on complex topography and the effects of stable stratification. In: Gayev Y.A., Hunt J.C. (eds) Flow and Transport Processes with Complex Obstructions. NATO Science Series, vol 236. Springer, Dordrecht
Over the last twenty five years a consistent picture of the structure and dynamics of canopy turbulence has emerged. We now know that there are fundamental differences between the structure of turbulent flow through uniform vegetation canopies and that in a boundary layer. The flow in and above the canopy, that is, in the ‘roughness sublayer’ resembles that in a plane mixing layer rather than a boundary layer. Turbulence production rates near the canopy top are much higher than in a boundary layer and characteristic large, energy-containing eddies, quite distinct from those in the boundary layer above are generated there by a hydrodynamic instability process. In the canopy, the dissipation rate of turbulence is also enhanced because boundary layers on the vegetation surfaces provide a source of intense shear layers with thicknesses of order the Kolmogorov lengthscale, augmenting those in the normal eddy cascade. This paper describes the way that this ‘standard’ picture of canopy turbulence is modified by topography so it is appropriate to set the scene with a brief history of how this standard picture was constructed. As scientific histories generally are, this will be a personal account, reflecting the line of discovery followed over the last three deacdes by the group
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