Unsteady Lift and Radiated Sound from a Wake Cutting Airfoil

An experimental study of the transient response of an airfoil to a passing wake, commonly known as wake cutting, has been carried out in order to contribute to the basic understanding of interaction between successive blade rows in turbomachinery. An open jet was traversed periodically by moving circular rods in pinwheel fashion and a periodic row of oblique wakes was created. An instrumented airfoil was placed in the jet and microphones were used to obtain the radiated field. By using periodic sampling and averaging technique on all signals, the random, turbulent portion was suppressed, and only the periodic component was extracted. The periodic component of the instantaneous chordwise surface pressure distribution on the airfoil and the radiated sound field from the airfoil were measured and compared with the existing theories.