Application of semi-empirical model to analysis of vortex-excited vibrations of beams near synchronisation region

This paper presents, the possibility of using a semi-empirical model similar to that proposed by Simiu and Scanlan to analyse the vortex-induced vibrations of beams. In particular, the behaviour of beams near and in the synchronisation region is considered. The motion equations of the system (beam and air) are obtained using the finite element method and the strip method. The aerodynamic excitation forces perpendicular to the wind flow direction are considered as a sum of forces due to the turbulence of oncoming flow, the forces caused by the vortex shedding and forces caused by the air-structure interaction. The forces due to the air-structure interaction are described by means of the model proposed by Simiu and Scanlan. The excitation forces caused by turbulence and by the vortex shedding are described using the Fourier series in time. The Fourier components of time series are determined on the basis of the appropriate power spectral density functions given in the literature. The time integration method is used to-obtain the transient and steady state solutions of motion equations. Several exemplary solutions for beams with cylindrical cross-section are obtained in the above-mentioned way. The results of calculations indicate that the typical dynamic behaviour of beams, observed in experiments; can be modelled if the aerodynamic constants appearing in the semi-empirical model have been appropriately chosen.