A method and apparatus to improve air flow in an air circulating fan assembly by forming an inlet opening in a fan assembly. A static air pressure profile is calculated along a top portion of the fan assembly configured to operate in an enclosure. The shape of a section of the inlet opening in the top portion of the fan assembly is changed based on a pressure contour of the calculated static air pressure profile. The method is repeated iteratively one or more times using an inlet opening changed by a previously calculated static air pressure profile when calculating a subsequent static air pressure profile. The inlet opening is positioned in the top surface of the fan assembly so that the centroid of the inlet opening is laterally offset with respect to the rotational axis of an impeller in the fan assembly.