The described embodiments relate generally to optimizing airflow in a computer system. By modifying the external surface of centrifugal cooling fan enclosures the pressure drop associated with airflow moving around the enclosures can be reduced. This is generally accomplished by rounding off hard edges from the outside of the cooling fan enclosure as well as forming cover surfaces rather than simply using flat cover surfaces. In some cases this can also involve modifying the shape of the fan inlet, or even contouring the shape of the cooling fan blades to allow air to flow more easily through the computer enclosure.