Measurements and simulations of airflow in a mechanically ventilated active facade.

Simplified methods to predict the flow between vertical plates cannot be applied to predict the flow patterns in active facades. Due to the presence of blinds and asymmetric inlet or outlet openings and heat transfer through the glazed surfaces (e.g. sun radiation), the flow is much more complex. This research provides an onset for a model that is capable of predicting the airflow in the cavity of an active facade (without any heat transfer). Therefore measurements and simulations are performed. The airflow is measured with two-dimensional Particle Image Velocimetry (PIV) and one-dimensional hot-film anemometry (HFA) under isothermal conditions. The measurements show some distinct flow features and low-frequency large-scale instationary behaviour and illustrate that the boundary conditions (e.g. dimensions of the inlet) have a major influence on the flow pattern in the facade. The results of Computational Fluid Dynamics (CFD) simulations are compared with the experimental results. It is shown that the two-dimensional CFD model is capable of predicting the general tendencies of the flow. The measurements suggest that the airflow in the facade is three-dimensional, which could not be confirmed by the steady three-dimensional simulations performed in this study.