Abstract
Façade geometrical details can substantially influence the near-façade airflow patterns and pressures. This is especially the case for building balconies as their presence can lead to multiple separation and recirculation areas near the façades and hence large changes in surface pressure distribution. Computational fluid dynamics (CFD) has been widely used to investigate the impact of building balconies, mainly based on the steady Reynolds-averaged Navier-Stokes (RANS) approach. The objective of the present study is to evaluate the performance of steady RANS and large-eddy simulations (LES) in predicting the near-façade airflow patterns and mean surface pressure coefficients (Cp) for a building with balconies for three wind directions θ = 0°, 90°, 180°, where 0° is perpendicular to the façade under study. The evaluation is based on validation with wind-tunnel measurements of Cp. The results show that both RANS and LES can accurately predict Cp on the windward façade for θ = 0° with average absolute deviations of 0.113 and 0.091 from the measured data, respectively. For the other two wind directions, LES is clearly superior. For θ = 90°, the average absolute deviations for RANS and LES are 0.302 and 0.096, while these are 0.161 and 0.038 for θ = 180°. Large differences are found in the computed flow fields on the balcony spaces. Because RANS systematically underestimates the absolute values of both Cp and mean wind speed on the balconies, it is suggested that building design based on RANS might result in excessive ventilation and in too high wind nuisance level.
Highlights
Building façade geometrical details such as balconies can signifi cantly affect the near-façade airflow patterns and the surface pressure distributions on building façades [1,2,3,4,5]
The objective of the present study is to evaluate the performance of steady Reynoldsaveraged Navier-Stokes (RANS) and large-eddy simulations (LES) in predicting the near-façade airflow patterns and mean surface pressure coefficients (Cp) for a building with balconies for three wind directions θ 1⁄4 0, 90, 180, where 0 is perpendicular to the façade under study
This paper evaluates the performance of steady RANS and LES in predicting the near-façade airflow patterns and mean surface pressure coefficient (Cp) for a building with balconies
Summary
Building façade geometrical details such as balconies can signifi cantly affect the near-façade airflow patterns and the surface pressure distributions on building façades [1,2,3,4,5]. The good performance of RANS approach in predicting the Cp on the windward façade of a building with balconies for both perpen dicular (θ 1⁄4 0 ) and oblique (θ 1⁄4 45 ) wind directions was shown in Ref. Such good performance could not be shown for the leeward façade, where steady RANS systematically underestimated the absolute value of Cp for the two wind directions [4]. This is mainly attributed to the well-known deficiencies of steady RANS in accurately reproducing flow separation, recirculation and reattachment, and its Reference (Murakami, 1990) [27] (Prianto & Depecker, 2002)
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