One- and two-equation models for canopy turbulence

The predictive skills of single- and two-equation (or K-ε) models to compute profiles of mean velocity (U), turbulent kinetic energy (K), and Reynolds stresses (u′w′) are compared against datasets collected in eight vegetation types and in a flume experiment. These datasets range in canopy height h from 0.12 to 23 m, and range in leaf area index (LAI) from 2 to 10m2 m-2. We found that for all datasets and for both closure models, measured and modelled U, K, and (u′w′) agree well when the mixing length (lm) is a priori specified. In fact, the root-mean squared error between measured and modelled U, K, and (u′w′) is no worse than published values for second- and third-order closure approaches. Within the context of one-dimensional modelling, there is no clear advantage to including a turbulent kinetic dissipation (ε) budget when lm can be specified instead. The broader implication is that the added complexity introduced by the e budget in K-ε models need not translate into improved predictive skills of U, K, and (u′w′) profiles when compared to single-equation models. © 2004 Kluwer Academic Publishers.

Duke Scholars

Author Gabriel G. Katul Civil and Environmental Engineering