Pressure coefficient simulated by CFD for wind-driven ventilation analysis

Pressure coefficients (C_P) are fundamental to calculate ventilation rates in buildings by the airflow network models (AFN). This paper deals with the use of CFD simulation to calculate C_P, and the use of those C_P values as input in building energy simulations (BES). The commercial package CFX was used to calculate C_P for a 5-stories isolated building, typically found in social housing complexes in Brazil, The standard k-ε turbulence model was adopted. The paper describes the software settings and discusses the importance of some guidelines prescriptions as mesh independence, adopted wind profile and the use of roughness in the domain floor. The C_P values were applied in the BES-AFN model TAS for the São Paulo-Brazil climate. The main conclusion is that mesh and the adopted wind profile have a strong influence in the calculated C_P values, and the guidelines prescriptions are relevant and should be followed. The BES-AFN results show large differences depending on the source of C_P data: the CFD simulation or the generic values found in the literature. Experimental validation is recommended to assess the better C_P source for AFN model.