In order to accurately predict the dynamic instabilities of a helicopterrotor/fuselage coupled system, nonlinear differential equations are derived and integrated in thetime domain to yield responses of rotor blade fl...In order to accurately predict the dynamic instabilities of a helicopterrotor/fuselage coupled system, nonlinear differential equations are derived and integrated in thetime domain to yield responses of rotor blade flapping, lead-lag and fuselage motions to simulatethe behavior of the system numerically. To obtain quantitative instabilities, Fast Fourier Transform(FFT) is conducted to estimate the modal frequencies, and Fourier series based moving-blockanalysis is employed in the predictions of the modal damping in terms of the response time history.Study on the helicopter ground resonance exhibits excellent correlation among the time-domain (TD)analytical results, eigenvalues and wind tunnel test data, thus validating the methodology of thepaper. With a large collective pitch set, the predictions of regressive lag modal damping from TDanalysis correlate with the experimental data better than from eigen analysis. TD analysis can beapplied in the dynamic stability analysis of helicopter rotor/fuselage coupled systems incorporatedwith nonlinear blade lag dampers.展开更多
文摘In order to accurately predict the dynamic instabilities of a helicopterrotor/fuselage coupled system, nonlinear differential equations are derived and integrated in thetime domain to yield responses of rotor blade flapping, lead-lag and fuselage motions to simulatethe behavior of the system numerically. To obtain quantitative instabilities, Fast Fourier Transform(FFT) is conducted to estimate the modal frequencies, and Fourier series based moving-blockanalysis is employed in the predictions of the modal damping in terms of the response time history.Study on the helicopter ground resonance exhibits excellent correlation among the time-domain (TD)analytical results, eigenvalues and wind tunnel test data, thus validating the methodology of thepaper. With a large collective pitch set, the predictions of regressive lag modal damping from TDanalysis correlate with the experimental data better than from eigen analysis. TD analysis can beapplied in the dynamic stability analysis of helicopter rotor/fuselage coupled systems incorporatedwith nonlinear blade lag dampers.
