Experimental study of the aeroacoustic mechanism of rotor–vortex interactions

The interaction of a naturally occurring vortex and an axial flow fan is investigated using cross‐correlation and real‐time observation techniques. Results show that the vortex produces a countersign acoustic source strength distribution over the span of the fan blade at the blade passage frequency. Evidence of the influence of the vortex structure on the fluctuating blade pressure measurements is derived from real‐time observations of on‐blade pressure measurements. The experiments indicate that the rotor–vortex interaction can be a significant source mechanism producing discrete‐tone fan noise.