Prescribed Wake Modifications To Account For Harmonic Rotor Loading And Validation with HART Data

A method is presented to approximately compute wake perturbations due to harmonic blade loading variations during its revolution. The source of the harmonic loading may be due to the operational condition of the rotor, the blade elasticity, or due to whatever source of active control. Based on blade element/momentum theory principles an induced velocity field is computed depending on the harmonic blade loading and approximated in terms of radial shape functions and a Fourier series. After transformation into the non-rotating cartesian hub coordinate system it is available for the computation of the tip vortex convection from the point of their generation downstream across the rotor disk. The complete formulation is given and results are validated with HART data.