Wind Driven Flow through Openings- A Review of Discharge Coefficients

This paper reviews the current literature on discharge coefficients (CD) of openings and compares different studies for wind-driven cross-ventilation. Considerable variation of discharge coefficients with opening porosity, configuration (shape and location in the faade), wind angle and Reynolds number is shown. Consequently, the use of a constant CD value such as that given in textbooks or other sources might be an invalid simplification. Scaling, upstream flow conditions, internal partitions and the assumptions of turbulent flow, sealed body and energy dissipation made for the application of the orifice equation should be considered in wind tunnel experiments of cross-ventilation.