Improved k–ε two-equation turbulence model for canopy flow

Abstract

A three-dimensional k–ε turbulence model was developed to examine air flow both through and above a small forest stand submerged in an otherwise undisturbed boundary-layer flow. The effects of the forest canopy were modeled conventially using a sink for momentum and a source for the generation of turbulence energy. In addition, a further sink was added to the k- and ε-budget equations to account for the additional loss of turbulence energy. The flow equations were solved using the PHOENICS fluid dynamic program by adding the necessary source/sink terms into the standard k–ε turbulence model. The thermal stratification is not included in the model simulation and wind tunnel experiment. Predictions from the model were compared against wind tunnel data, and good agreement was observed. Moreover, three different canopy shapes of the forest were introduced into the simulation. With the wind tunnel data as a reference, their results were compared and some useful conclusions were drawn. Finally, a design case study analyzed the effect of canopies on the wind environment of urban micro-climates. It showed that the developed tree canopy model is applicable in the design and evaluation stage.