Rotor aerodynamics and dynamics Rotor aerodynamics

The linear aerodynamic theory used in Level 1 rotor modelling is a crude approximation to reality and, while quite effective at predicting trends and gross effects, has an air of sterility when compared with the rich and varied content of the fluid dynamics of the real flow through rotors. Compressibility, unsteadiness, three-dimensional and viscous effects have captured the attention of several generations of helicopter engineers; they are vital ingredients for rotor design, but the extent of the more ‘academic’ interest in real aerodynamic effects is a measure of the scientific challenge intrinsic to rotor modelling. It is convenient to frame the following discussion into two parts – the prediction of the local rotor blade angle of incidence and the prediction of the local rotor blade lift, drag and pitching moment. While the two problems are part of the same feedback system, e. g., the incidence depends on the lift and the lift depends
on the incidence, separating the discussion provides the opportunity to distinguish between some of the critical issues in both topics.