Unsteady airloading panel method for prop-fans
An unsteady, linear, compressible, three dimensional lifting surface panel method is presented for use with propellers and prop-fans. Both gust and blade vibration problems can be treated. Derivation of the theory is based on the acceleration potential method and can be considered a generalization of the analogous wing theory to include rotation and multiple blades. As with the wing methods, the integral equation is discretized and solved by matrix inversion. Sample calculations are use to explore the difference between 2D and 3D results and the significance of unsteadiness in angular inflow calculations for propellers. It is shown at the once-per-revolution frequency of propellers, that quasi-steady methods should be adequate. At the high frequencies of interest in noise analysis, 2D strip methods give adequate results away from blade tips. For flutter, frequencies lie in an intermediate range where a full 3D unsteady technique seems to be required.