Abstract:
The paper describes a methodology to extract linearized state-space dynamic inflow model from a generic and high fidelity aerodynamic analysis for single and coaxial helicopter rotor systems. Both hover and forward flight are studied including maneuvering and the results are demonstrated by a free-wake analysis. The proposed methodology which is founded on a Single Frequency Analysis is computationally efficient and provide the entire frequency-domain behavior of the wake inflow states. Besides being able to incorporate any advanced computational tool, the present methodology takes advantage of exact wake states and thus adequately encompasses high frequency responses. The paper also extends the methodology to the case where states of higher harmonics are required and to the case of heaving, rolling and pitching rotor disc. For a single rotor system the results resemble the well known classical dynamic inflow model. For coaxial rotor system in hover, the high mutual couplings between the rotors are clearly demonstrated and affect the resulting system matrices. An important feature of the present methodology lays in the fact that the entire formulation is non-dimensional and the in-flow analysis is completely separated from the loads analysis, which enables a consistent generalization of the results.