Modal characterisation of a rotor/propeller rig for tip-mach scaled wind tunnel testing

An advanced rotor and propeller rig for tip Mach-scaled wind tunnel testing is the subject of dynamic analysis presented in this paper. Experimental modal analysis and finite element method are used to assess the key characteristics such as the modal properties and transfer functions, as well as their changes under varying conditions. This work aims to determine and summarize these characteristics for the purposes of further rig development and its safe operation. The research also includes analysis of the key sources of uncertainty, damping, the effect of unbalanced excitation and model-experiment correlation. The low frequency region is found to be dominated by the three weakly damped global modes whilst the following modes feature increased modal activity of the rotor shaft and the hub. The latter set of modes is also found to be more susceptible to nonlinear effects and associated increased identification and modelling uncertainty.