An experimental investigation of the reduced frequency effects into pressure coefficients of a plunging airfoil

Aerodynamic coefficients on a two dimensional plunging airfoil, in a low-speed wind tunnel are presented. Dynamic motion was produced by plunging the model over a range of reduced frequencies, and mean angles of attack. The Reynolds number in the present test was held fixed (Re=1.5x10(5)), and the reduced frequency was varied in an almost wide range. Surface static pressure distribution was measured on the upper and lower sides of the model, during the oscillating motion. It was found that reduced frequency had strong effects on the pressure distribution, near the leading edge of the airfoil. For mean equivalent angles of attack of 0, 5 degrees, hysteresis loops on the upper surface of the airfoil near the leading edge were counter clockwise and for high mean equivalent angle they were clockwise. By increasing the reduced frequency the hysteresis loops became wider and larger.