A Fully Nonlinear Version of the Pitt-Peters Dynamic Inflow Model in Axial Flow

This paper develops a set of nonlinear influence coefficients for the Pitt-Peters inflow model rendering it completely nonlinear in all variables. The purpose of this paper is to represent the nonlinear integrals in closed-form, thus allowing the fully nonlinear model to be used in flight simulators. There are several cases for which integrals need to be calculated differently. Those cases are generalize such that the final formulas can be used for any condition. Equations are developed for thrust, moment, and second moments in a matrix form that allows simple modification of the existing Pitt-Peters [L] matrix to include all nonlinearities. The resultant model may then be used for flight maneuvers in which the net flow direction at the rotor disk (and the existence of windmill or powered state) need not be uniform across the rotor disk.