Active control of sheet flutter by using injection and suction air flows from a nozzle

This paper presents a novel technique of an active control to suppress sheet flutter. In this technique, sheet flutter is actively and non-contactly suppressed by injection and suction air flows through a nozzle. A nozzle is combined with a speaker as an actuator, and this device is drove in a sheet displacement feedback system. PET sheet is used as a controlled object, and the sheet is supported upper end in a wind tunnel. To show the effectiveness of this technique for sheet flutter suppression, the suppression characteristics are experimentally examined. Then, the suppression effectiveness is evaluated at the increased rate of the flutter velocity with control as compared to it without control. Moreover, air flow patterns around the nozzle and the sheet during control are visualized by the smoke wire method. Lastly, the control effects by injection and suction air flows to the sheet are examined in terms of air flow patterns, frequency response characteristics, and unsteady pressure. As a result, this paper shows the effectiveness of the proposed device and technique for sheet flutter suppression, and the flutter velocity is increased by 50 % with control as compared to without control. In this technique, the injection and suction air flows from the nozzle change the airflow around the sheet, not directly apply momentum on the sheet. Therefore, this technique is an air flow control.