Modified ‘closure’ constants of the Standard k–ε turbulence model for the prediction of wind-induced natural ventilation

Abstract

In this study, wind-driven natural ventilation in buildings is investigated by means of computational fluid dynamics. The airflow in and around three pilot buildings, which correspond to the most common natural-ventilation designs, i.e. cross-, windward- and leeward- single-sided ventilation, is simulated by applying both the Standard and a modified k–ε turbulence model. The latter represents a Prandtl number-modified version of the Standard k–ε model, based on the flow-variable (velocity and turbulence variables) distributions and on the atmospheric boundary layer (ABL) assumptions. Numerical results of streamwise and vertical velocity components, as well as of pressure coefficients at the facades, obtained by both turbulence models are compared with available wind tunnel experimental data found in literature. It is concluded that both models applied are in acceptable agreement with measurements, especially for the mean streamwise velocity component, while the proposed modified model is more accurate as far as flow within the windward and the internal parts (i.e. within the building) of the domain is concerned. Practical application: This study focuses on the development of a modified k–ε turbulence model for the prediction of wind-driven natural ventilation. The analysis described represents a methodology to produce ‘closure’ parameters, such as Prandtl numbers, compatible with the incoming wind characteristics (ABL). It was found that for all ventilation cases studied, i.e. cross- and single-sided ventilation, the proposed modified model is more accurate compared with the Standard k–ε model, and it accounts for the dumping effect near the walls and for kinetic energy reduction in the impinging region adequately. It is satisfying that the modified k–ε model leads to acceptable engineering results within relatively practical computer resources.