A vortex-producing fan controller uses a variable-speed vortex-producing fan positioned above a server rack to create a helical airflow within the server rack that couples with cooled air entering a data center through a floor opening situated near a bottom of the server rack. A speed of the variable-speed vortex-producing fan and a flow rate of the cooled air coupled within the helical airflow up through the server rack are adjusted responsive to changes in input air temperature of air entering the variable-speed vortex-producing fan detected using a fan input air temperature sensor positioned above the server rack.