Energy and Buildings 118 (2016) 142–151 Contents lists available at ScienceDirect Energy and Buildings j ourna l ho me pa g e: www.elsevier.com/locate/enbuild How temperature affects the airflow around a single-block isolated building F. Nardecchia ∗ , F. Gugliermetti 1 , F. Bisegna 1 SAPIENZA University of Rome, Department of Astronautical, Electrical and Energy Engineering, Via Eudossiana 18-00184 Rome, Italy a r t i c l e i n f o Article history: Received 16 February 2016 Received in revised form 29 February 2016 Accepted 1 March 2016 Available online 4 March 2016 Keywords: Ventilation Solar radiation CFD Urban environment a b s t r a c t This study examines the influence of outdoor phenomena together with temperature changes around an isolated building. Considering different wind velocities, temperature differences and building heights, several numerical CFD simulations were performed to investigate the effect of the temperature on the recirculation zones, for various characteristics of the ambient flow field. In the first part, the temperature effects between undisturbed air and building surface were analyzed together with their impact on the flow field. In the second part it was also taken into consideration the influence of the solar radiation. Finally the study was completed by evaluating how different building geometries can affect the previous scenarios. The results show the importance of the temperature variation for the ventilation around the building and how it modifies, in a significant way, the fluid dynamics close to the building envelope. The cor- relations found allow to make a proper estimation of the extent of the recirculation regions near the building. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Natural ventilation can give an important contribution to the environmental sustainability and energy efficient buildings. This is the reason why, recently, scientific researchers tried to eval- uate outdoor and indoor ventilation around buildings. Natural ventilation can be caused by: wind induced by pressure, pressure differences due to temperature changes, or a combination of both. Linden [1], examining two kinds of ventilation, that is mixing and displacement ventilations, determined the rules driving them and established how air moves within a building. Hunt and Linden [2] and Heiselberg et al. [3] studied transient draining flows in a space containing buoyant fluid. Larsen et al. [4] investigated deeply the effect of the ventilation in a room with an opening and Karava et al. [5,6] reviewed the current literature about discharge coefficients of natural ventilation openings. Ventilation performances can be evaluated through experimen- tal techniques, analytic and semi-empirical formulas, simulations ∗ Corresponding author. Fax: +39 064880120 E-mail addresses: fabio.nardecchia@uniroma1.i (F. Nardecchia), franco.gugliermetti@uniroma1.it (F. Gugliermetti), fabio.bisegna@uniroma1.it (F. Bisegna). 1 Fax: +39 064880120. with zonal network models and multizone models, and numerical tools, as Computational Fluid Dynamics (CFD) models. Experimental techniques are experiments performed in wind tunnels. Through this method Murakami et al. [7], Kato et al. [8] and Ji et. al [9] studied wind components, while Etheridge and Nolan [10] and Jiang et al. [11] examined turbulence models in small confined environments. Karava et al. [12–14] also analyzed the air movement in this kind of environment, while Kato et al. [15] and Bu et al. [16] applied their studies on big area studies. Etheridge et al. [17–19] adopted analytic studies to perform sim- ple or complex parametric analysis, as the one where he suggested to use dimensionless graphs for the building envelope design, in order to increase natural ventilation performances. Còstola et al. [20] recommended a method for the study of air infiltration and ventilation using the pressure coefficients as input parameters. As previously said, simulations with zonal network and multizone models are a different way to examine this phenomenon, as Còs- tola et al. [21] for the network model, or Li et al. [22] for single-zone and multizone buildings, demonstrated the efficacy of these models in the presence of multiple openings. Then Hensen [23] investi- gated the combination of network modeling and thermal building models. However, despite all these works, Chen [24], while analyzing the devices used to predict the ventilation performance around http://dx.doi.org/10.1016/j.enbuild.2016.03.003 0378-7788/© 2016 Elsevier B.V. All rights reserved.