Free shear layer control and its application to fan noise

Free shear layers are known to be sensitive to the imposed perturbations or geometrical variations at the origin of the flow. The streamwise development of the free shear layer can be effectively controlled by using this property. In this experiment, we have found that the flow pattern of a wake or a mixing layer can be dramatically changed by applying suction at the trailing edge of the splitter plate. In an axial fan, the noise is produced by the interaction of the rotor wake and the stator. By altering the characteristics of the wake, the noise is expected to be greatly modified. In the present study, we demonstrate that the wake-blade flow can be stabilized by the combination of suction and a thin control rod.