An inverse aeroacoustic problem with aerodynamic constraint for a helicopter rotor

An inverse aeroacoustic model on helicopter rotor combined with aerodynamic constraint is proposed based on Ffowcs Williams and Hawkings equation in subsonic condition. This method is suitable especially for tip region with thin blade thickness. The thickness noise is associated with geometry and motion condition. In this way the pressure loading on the wall is associated with far-field noise measurement. Once the equation can also be established, the pressure loading on the wall can be obtained by solving this equation. Since this equation is an ill-posed problem, the singular value decomposition combining with regulation method is applied. Besides, some constraint conditions based on aerodynamics are considered. This is equivalent to convert the regularization problem into an optimization problem under constraint conditions. A test was performed to verify the algorithm on a rotor with two blades. The pressure distribution of several different cross section positions is compared with the experimental data. The reconstruction results agree well with the experimental data. The effect of interference noise is also been considered, at low signal noise ratio condition, the reasonable results can also be obtained.