Using CFD to Evaluate Natural Ventilation through a 3D Parametric Modeling Approach

Nayara Rodrigues Marques Sakiyama,Timea Bejat,Jurgen Frick,Harald Garrecht

doi:10.3390/en14082197

Abstract

Predicting building air change rates is a challenge for designers seeking to deal with natural ventilation, a more and more popular passive strategy. Among the methods available for this task, computational fluid dynamics (CFD) appears the most compelling, in ascending use. However, CFD simulations require a range of settings and skills that inhibit its wide application. With the primary goal of providing a pragmatic CFD application to promote wind-driven ventilation assessments at the design phase, this paper presents a study that investigates natural ventilation integrating 3D parametric modeling and CFD. From pre- to post-processing, the workflow addresses all simulation steps: geometry and weather definition, including incident wind directions, a model set up, control, results’ edition, and visualization. Both indoor air velocities and air change rates (ACH) were calculated within the procedure, which used a test house and air measurements as a reference. The study explores alternatives in the 3D design platform’s frame to display and compute ACH and parametrically generate surfaces where air velocities are computed. The paper also discusses the effectiveness of the reference building’s natural ventilation by analyzing the CFD outputs. The proposed approach assists the practical use of CFD by designers, providing detailed information about the numerical model, as well as enabling the means to generate the cases, visualize, and post-process the results.

Highlights

Wind-driven natural ventilation is an attractive passive alternative in light of the challenges imposed by climate change and sustainable goals
The procedure was only applied to computational fluid dynamics (CFD) 2, where all openings were modeled without frames
Data recorded with closed windows (7:00 a.m.–8:59 p.m.) were excluded, and the remaining readings were grouped and averaged given the same angle range used in CFD

Summary

Introduction

Wind-driven natural ventilation is an attractive passive alternative in light of the challenges imposed by climate change and sustainable goals. Natural ventilation is highly variable as it is driven by the climatic forces of wind (wind effect) and temperature (stack effect), which makes it challenging to estimate ventilation rates, an essential parameter for natural ventilation assessment. Different methods can be employed to address this task, including standards [5,6], guidelines [7,8], charts based on parametric analysis [9], empirical calculations [10], direct and indirect measurements [11], and building simulations [12,13,14,15].

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Conclusion