UNSTEADY AERODYNAMIC RESPONSE OF A CASCADE TO NONUNIFORM INFLOW

A solution method is developed for the small perturbation approximation to the inviscid, unsteady fluid equations for a two-dimensional cascade of airfoils. By introducing the unsteady field as a locally small perturbation from a nonuniform steady field, a first-order coupling between the unsteady fluid properties and the gradients of the steady field properties results. Results of this analysis procedure are compared with the experimentally determined unsteady pressure distribution on the vane of a low-speed research compressor produced by the wakes from the upstream rotor. Correlation between experimental and analytical results is good. Similar comparisons of the data with an analysis method that approximates the vane as a two-dimensional cascade of flat plates at zero mean incidence did not exhibit acceptable correlation. The lack of correlation was particularly evident for the chordwise phase angle distribution.