Measurement of unsteady aerodynamic force on a galloping prism in a turbulent flow : a hybrid aeroelastic-pressure balance

This paper proposes a novel hybrid aeroelastic-pressure balance (HAPB) technique for the measurement of unsteady aerodynamic force on a galloping prism. HAPB wind tunnel tests were performed to simultaneously observe the unsteady aerodynamic force and galloping response of a test model. The amplitude-dependent nonlinear damping and stiffness of the HAPB system that include the non-wind-induced aerodynamic force that is caused by the interaction between the oscillating model and its surrounding ‘still’ air were identified using a wavelet method. The non-wind-induced aerodynamic force was determined by a forced vibration technique. Subsequently, the galloping response was calculated by substituting the unsteady aerodynamic force and physical nonlinearities into the governing equation of motion. The results show that (1) the proposed HAPB technique is effective in obtaining unsteady crosswind forces; (2) the unsteady self-excited force with excluding the non-wind-induced aerodynamic force can accurately predict the galloping response of the test model whereas the classical quasi-steady theory fails for the prediction. This study has not only provided a HAPB used in wind tunnel, but also addressed shortcomings of the classical quasi-steady theory in predicting galloping instabilities of slender prisms.