Integrated airloads-inflow model for use in rotor aeroelasticity and control analysis

This paper introduces an integrated airloads-inflow model that is ideally suited for rotor aeroelasticity and control analysis, especially for cases in which eigenvalues are desired. The airloads model is derived from a rigorous application of thin-airfoil theory with an extension to allow for other airfoil effects, including ONERA type dynamic stall. The result is a hierarchical lift model that can be simplified down to any level including conventional 2-D strip theory. The inflow model is a complete 3-D representation of shed and trailing vorticity with a skewed cylindrical wake. The inflow is expanded in shape functions which can be truncated to any desired texture. Both models are written in closed-form state-variable equations with no hidden states and no integrals over the wake. The coupling between these models (and with any structural model) is effected through simple geometric relationships (with no limit on rigor) and through the use of special lift modes. The result is a unified rotor analysis in terms of ordinary differential equations for lift, inflow, and structure.