Correlation of measured induced velocities with a finite-state wake model

A new rotor induced-flow model is applied to the correlation of a recent set of LDV inflow measurements made by the Army Labs at NASA Langley. This new inflow model is based on an acceleration potential with a skewed cylindrical wake. While this particular flow description is not new, the novel aspect of the present work is that the model is not discretized. Instead, the flow field and the rotor lift are expanded in terms of appropriate inflow modes. The result is a set of closed-form, first-order, ordinary differential equations in time that defines a finite number of modal inflow states, with blade lift as the forcing function. Although the model is intended primarily as a representation of unsteady aerodynamics for aeroelasticity applications, the results here show that it is also effective as a means of finding the inflow distribution in forward flight.