Wind tunnel analysis of flow and dispersion in cross-ventilated isolated buildings: Impact of opening positions

Abstract

a b s t r a c tThis paper presents a detailed experimental analysis of flow and dispersion by cross-ventilation in five generic isolated single-zone buildings with different opening positions. First, flow visualization is performed illustrating the highly transient flow and dispersion process dominated by a flapping jet with pronounced Kelvin-Helmholtz instabilities. Next, the mean velocity field, the turbulent kinetic energy field, the mean concentration field and the concentration fluctuation field are presented and analyzed. Finally, time histories of the instantaneous concentration in the building are provided. The contaminant dispersion in the cross-ventilated flow is strongly influenced by the overall flow pattern that is largely determined by the inlet opening position, while the outlet opening position seems less important. The results provide new insights in the flow and dispersion process inside cross-ventilated buildings and can be used to validate Computational Fluid Dynamics (CFD) simulations of flow and dispersion by crossventilation and for the subsequent establishment of new CFD best practice guidelines. It is also shown that the use of different ventilation performance parameters yields a different ranking of the configurations in terms of ventilation performance. Care should therefore be applied when evaluating ventilation performance based on only flow rates or velocities as opposed to dispersion quantities.

Impact of windward inlet-opening positions on fluctuation characteristics of wind-driven natural cross ventilation in an isolated house using LES

“…Despite these differences, there are some points that can be contrasted and discussed. First, the current study agrees with those of Karava et al [11] and Tominaga et al [9] regarding the nature of the recirculation region in terms of vortex centre, size, and sense of rotation being mainly governed by inlet opening position. Second, the current study focuses on horizontal opening positions concluding that an opening near the centre of the windward face can provide for a greater ventilation rate for the building with openings located at lateral positions.…”

“…Studying natural ventilation by experimental methods has been tested in many types of buildings for numerous reasons, though usually through two principal, though complicated and expensive, methods during research: wind tunnels [3][4][5][6][7][8][9][10][11] and field measurements for existing buildings [12][13][14]. Karava et al [11] tested six cases of inlet-outlet vertical opening positions on opposite walls and four cases on adjacent walls in natural cross ventilation; they found that the inlet-to-outlet ratio and the relative location of openings on a building's façade are important parameters that must be considered in addition to wall porosity.…”

“…Karava et al [11] tested six cases of inlet-outlet vertical opening positions on opposite walls and four cases on adjacent walls in natural cross ventilation; they found that the inlet-to-outlet ratio and the relative location of openings on a building's façade are important parameters that must be considered in addition to wall porosity. Tominaga et al [9] analysed five configurations of inlet-outlet vertical configuration on field flow and dispersion of contaminants in cross-ventilated buildings and their results provide new insights into the flow and dispersion processes inside naturally cross-ventilated buildings, and can be used in computational fluid dynamics (CFD) validations of flow and dispersion.…”

Validation Methods of Geometric 3D-CityGML Data for Urban Wind Simulations

“…3D-Buildings of the area of interest are imported into the ICEM-CFD as STL format, the boundary conditions (inlet, outlet, wall, and symmetry) are identified precisely, taking into consideration the direction of the wind. There are some guidelines suggested by different researchers for the definition of the solution domain for simulations of flows in urban areas [19]. It is recommended to set the domain size 5 times larger than the tallest existed building within the processed area and both the inlet and outlet set far enough from the tallest building.…”

Influence of the geometrical parameters of urban canyons on the convective heat transfer coefficient

“…This study will concentrate on the analysis of a particular urban configuration: the urban canyon. The geometry of the urban canyon is often described by a single parameter, the canyon aspect ratio (H/W), which is defined as the ratio of the building height, H, to the width between buildings, W. In literature several authors have studied the street canyons, through numerical simulations [3], wind tunnel experiments [4][5][6], measurement campaigns [7], and comparison between numerical model and measurements campaign on a canyon scale model [8]. In literature, there are typically twodimensional studies [3,9].…”