Linearized Unsteady Lifting Surface Theory of a Lightly Loaded Propeller in an Inclined Flow

摘要

This report presents the detailed development of a linearized unsteady lifting surface theory for calculating the blade loadings of a lightly-loaded propeller operating in a slightly inclined flow. A numerical approach was developed and programmed to solve the integral equation of the theory which relates the unknown blade loads with the normal-to-the-blade velocities. The numerical procedure applies the mode approach and collocation method in conjunction with the generalizeid lift-operators. The effect of flow inclination on the blade bending moments is demonstrated to be significant. The across-the-disk component of the inclined inflow into the propeller in the primary contributor to the shaft frequency harmonic of blade bending moment. The effect, however, of the helical wake distortion due to shaft inclination adds very little to the amplitude of the shaft frequency blade bending moment.