Effect of Reduced Frequency on the Aerodynamic Behavior of an Airfoil Oscillating in a Plunging Motion

A series of low speed wind tunnel tests were conducted to study the unsteady aerodynamic behavior of an airfoil sinusoidally oscillating in plunge. The experiments included measuring the surface pressure distribution over a range of reduced frequencies; k = 0.03 - 0.06. In addition, steady state data were acquired and were used to furnish a baseline for further analysis and comparison. The model was oscillated with amplitude of +/- 15 cm and at three different mean angles of attack of 0 degrees, 10 degrees and 18 degrees. The unsteady aerodynamic loads were calculated from the surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces. The plunging displacements were transformed into the equivalent angle of attack. Variations of the pressure coefficients and aerodynamic loads with the equivalent angle of attack showed strong sensitivity to the reduced frequency and mean angles of attack.