CFD simulation of cross-ventilation for a generic isolated building: Impact of computational parameters

Abstract

• Extensive literature review on numerical cross-ventilation studies in overview table.• Detailed sensitivity analysis for CFD simulations of a cross-ventilated building model.• The SST k-ω turbulence model shows the best agreement with PIV measurements.• The turbulent kinetic energy strongly influences the convergence and the results.• The prediction of the outdoor standing vortex largely affects the indoor airflow. AbstractAccurate CFD simulation of coupled outdoor wind flow and indoor air flow is essential for the design and evaluation of natural cross-ventilation strategies for buildings. It is widely recognized that CFD simulations can be very sensitive to the large number of computational parameters that have to be set by the user. Therefore, detailed and generic sensitivity analyses of the impact of these parameters on the simulation results are important to provide guidance for the execution and evaluation of future CFD studies. A detailed review of the literature indicates that there is a lack of extensive generic sensitivity studies for CFD simulation of natural cross-ventilation. In order to provide such a study, this paper presents a series of coupled 3D steady RANS simulations for a generic isolated building. The CFD simulations are validated based on detailed wind tunnel experiments with Particle Image Velocimetry. The impact of a wide range of computational parameters is investigated, including the size of the computational domain, the resolution of the computational grid, the inlet turbulent kinetic energy profile of the atmospheric boundary layer, the turbulence model, the order of the discretization schemes and the iterative convergence criteria. Specific attention is given to the problem of oscillatory convergence that was observed during some of these coupled CFD simulations. Based on this analysis, the paper identifies the most important parameters. The intention is to contribute to improved accuracy, reliability and evaluation of coupled CFD simulations for cross-ventilation assessment.

CFD analysis of cross-ventilation of a generic isolated building with asymmetric opening positions: Impact of roof angle and opening location

“…Convergence is assumed to be obtained when all the scaled residuals leveled off and reached a minimum of 10 -6 for x and y momentum, 10 -5 for z momentum and 10 -4 for k, ε and continuity. As also observed by Ramponi and Blocken [29,30], the simulations showed oscillatory convergence. To obtain a reliable steady value of the solution variables, the results are monitored over 10,400 iterations and the variables are calculated by averaging over 400 iterations (10,000-10,400), after the simulation reached a statistically stationary solution.…”

“…The mean velocity vector field in the vertical center plane by PIV measurements and CFD simulations is shown in Figure 4a Ramponi and Blocken [30], the simulations overestimate the mean velocity around the opening, where the PIV measurements cannot provide accurate predictions due to reflections and shading effects [27]. Despite these differences an overall good agreement is observed.…”

“…Many research efforts focused on group (1) (e.g. [18][19][20][21][22][23][24][25][26][27][28][29][30]). Within this group, there are studies on the effect of the opening size (wall porosity) [19,21,23,26,27,29], the inlet-outlet opening ratio and location [21,23,25,27,29] and the building aspect ratio [22,28].…”

“…[62,63]). In the past 50 years, CFD has developed into a powerful tool for studies in urban physics and building aerodynamics [64], including natural ventilation in buildings, as demonstrated by review and overview papers [30,[64][65][66][67][68][69][70][71]. In this paper, the coupled approach (e.g.…”

“…In this paper, the coupled approach (e.g. [29,30,42,47,48,50,63,72]) is employed using the 3D [27]. For more information related to the wind-tunnel experiments the reader is referred to [27].…”