Research on Airfoil Stall Suppression Control by Use of a Smart-structure Device

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After the laminar boundary layer separates from the airfoil surface, the flow can reattach to the surface as a turbulent shear layer. This region between the laminar separation and the reattachment is called a laminar separation bubble. When the airfoil stalls, the laminar separation bubble burst occurs. The stall characteristics of the airfoil are strongly dependent upon the laminar separation bubble. It is also known that a low frequency oscillation is observed inside the laminar separation bubble near stallThe purpose of this research is to investigate the laminar separation bubble burst and to construct a method to suppress the airfoil stall. For this purpose, the following research items were investigated, firstly to extend the knowledge on an unsteady flow behavior of the laminar separation bubble, secondly to confirm the effect of burst suppression device on the airfoil, and finally to control the flow around the airfoil by use of a smart-structure device to control the airfoil stallThe conclusions of the present research are as follows.1) It was revealed the unsteady nature of the laminar separation bubble near stall.2) Burst suppression control plate was successfully applied for the airfoil to control the airfoil stall.3) Smart-structure device was also applied for the stall suppression. Some benefit was observed by use of this device.4) The behavior of the laminar separation bubble formed on a cambered plate wing, that has a different cross section compared with an ordinary airfoil, was also investigated.