A fan system comprising: an orifice having an opening disposed therethrough, the orifice having an inner surface, the inner surface having a smooth slope and comprising: a converging section; a diverging section; and a minimum radius section disposed between the converging section and the diverging section; a fan disposed in the fan orifice, the fan having a central hub that couples one or more blades that rotate about a y-axis parallel to a length of the hub, the fan comprising: a top tip proximate an end of a trailing edge of each blade, the top tip being disposed at a height (h 2) from a top surface of the orifice; a bottom tip proximate an end of a leading edge of each blade, the bottom tip being a bottom point of the blade; a fan height, being a maximum distance between the leading edge and the trailing edge in a direction along the y-axis; an edge between the top tip and the bottom tip; and a fan diameter, a minimum clearance (d 0) comprising a first distance along an x-axis within a plane of rotation of the fan normal to the y-axis between a portion of the minimum radius section of the inner surface of the orifice and the top tip of the fan; and a maximum clearance (d 3) comprising a second distance along the x-axis between a portion of the converging section of the inner surface of the orifice and the bottom tip of the fan; wherein an axial distance along the y-axis between the top tip and a bottom surface of the orifice is between approximately 0.85 and 0.95 times the fan height, and wherein, in use, air flows through the opening in the orifice in a direction parallel to the y-axis from the bottom surface to the top surface of the orifice. an orifice having an opening disposed therethrough, the orifice having an inner surface, the inner surface having a smooth slope and comprising: a converging section; a diverging section; and a minimum radius section disposed between the converging section and the diverging section; a converging section; a diverging section; and a minimum radius section disposed between the converging section and the diverging section; a fan disposed in the fan orifice, the fan having a central hub that couples one or more blades that rotate about a y-axis parallel to a length of the hub, the fan comprising: a top tip proximate an end of a trailing edge of each blade, the top tip being disposed at a height (h 2) from a top surface of the orifice; a bottom tip proximate an end of a leading edge of each blade, the bottom tip being a bottom point of the blade; a fan height, being a maximum distance between the leading edge and a top tip proximate an end of a trailing edge of each blade, the top tip being disposed at a height (h 2) from a top surface of the orifice; a bottom tip proximate an end of a leading edge of each blade, the bottom tip being a bottom point of the blade; a fan height, being a maximum distance between the leading edge and the trailing edge in a direction along the y-axis; an edge between the top tip and the bottom tip; and a fan diameter, a minimum clearance (d 0) comprising a first distance along an x-axis within a plane of rotation of the fan normal to the y-axis between a portion of the minimum radius section of the inner surface of the orifice and the top tip of the fan; and a maximum clearance (d 3) comprising a second distance along the x-axis between a portion of the converging section of the inner surface of the orifice and the bottom tip of the fan; wherein an axial distance along the y-axis between the top tip and a bottom surface of the orifice is between approximately 0.85 and 0.95 times the fan height, and wherein, in use, air flows through the opening in the orifice in a direction parallel to the y-axis from the bottom surface to the top surface of the orifice. an edge between the top tip and the bottom tip; and a fan diameter, a minimum clearance (d 0) comprising a first distance along an x-axis within a plane of rotation of the fan normal to the y-axis between a portion of the minimum radius section of the inner surface of the orifice and the top tip of the fan; and a maximum clearance (d 3) comprising a second distance along the x-axis between a portion of the converging section of the inner surface of the orifice and the bottom tip of the fan; wherein an axial distance along the y-axis between the top tip and a bottom surface of the orifice is between approximately 0.85 and 0.95 times the fan height, and wherein, in use, air flows through the opening in the orifice in a direction parallel to the y-axis from the bottom surface to the top surface of the orifice.