Wind tunnel and numerical study of wind pressure coefficients on a medieval Swedish church

Abstract

Air infiltration has great importance regarding energy, comfort, moisture and dust deposition in naturally ventilated historical buildings like churches. In these buildings, air infiltration is driven by stack effect and wind. When assessing the wind effect, reasonable estimation of wind pressure coefficients is crucial. Local wind pressure coefficients are significantly affected by the shape of the building and turbulence generated by its geometrical features, which – for moderately large churches – typically consist of main building body and window recesses, gable roof, tower, apse, and sacristy. To yield practically useful pressure coefficients, this study conducted wind tunnel and numerical investigations at a church, with gradual addition of these features. Wind pressure was measured on a small-scale model in a wind tunnel, while computational fluid dynamics (CFD) simulations were carried out for both small-scale and full-scale models. By comparing the experimental and numerical results, the SST k−ω turbulence model showed the best accuracy, yielding CFD results in good agreement with wind tunnel measurements. Most challenging was predicting the strong negative wind pressures occurring on a flat roof. Building structures like tower, apse, and sacristy had significant impact on the wind pressures on the central, main building body. This study adds knowledge on wind pressure effects by commonly occurring building components, with particular reference to churches and similar buildings. It was an important basis for developing further models for calculating the wind pressure coefficient.