A Note on Two-Equation Closure Modelling of Canopy Flow

The note presents a rational approach to modelling the source/sink due to vegetation or buoyancy effects that appear in the turbulent kinetic energy, E, equation and a supplementary equation for a length-scale determining variable, φ, when two-equation closure is applied to canopy and atmospheric boundary-layer flows. The approach implements only standard model coefficients C _φ1 and C _φ2 in the production and destruction terms of the φ equation, respectively. Numerical tests illustrate the practical applicability of the method, where, for example, simulations with the E–ω model (where is the specific dissipation and is the dissipation rate of E) properly reproduce both the surface-layer wind profile estimated from the Monin-Obukhov similarity theory and the mixing-height evolution observed above forested terrain in Southern Finland.