Design and initial testing of a facility to measure unsteady pressures on an oscillating cascade with supersonic leading edge locus

The development of analytical codes to predict the lift and moment coefficients on an airfoil in an oscillating cascade with a supersonic leading edge locus (SLEL) has generated a need to obtain unsteady experimental pressure data to validate the codes. A facility to gather such data was designed and constructed at the Ohio State University Aeronautical and Astronautical Research Laboratory, and unsteady pressure data was collected for a cascade oscillating at zero stagger angle. Unsteady pressures were measured for reduced frequencies ranging from.025 (26 Hz.) to.159 (166 Hz.), based on half chord.;An experimental influence coefficient technique originally developed for subsonic and transonic cascades was extended to the case of a cascade with a SLEL. This technique was developed to obtain the unsteady pressure difference coefficient on an airfoil in a cascade of airfoils, all of which were executing constant amplitude oscillations at a constant interblade phase angle. This influence coefficient technique allowed the measurement of the pressures by oscillating one airfoil at a time. In order to extend the influence coefficient technique to the measurement of unsteady pressures on a cascade with a SLEL, it was first necessary to derive the equations applicable to a SLEL cascade. The unsteady pressure on a reference airfoil due to all of the airfoils oscillating was then the sum of the influence coefficients from each airfoil.