Assessment of reduced models for the detection of modal interaction through rotor stator contacts

Interactions through direct contact between blade-tips and outer casings in modern turbomachines require complex formulations and subsequent expensive computational efforts when the classical finite element method is considered. The construction of reduced-order models through component mode synthesis techniques usually improves the computational efficiency and may be used for fast parameter studies yielding a better knowledge of the phenomena of interest. In this highly nonlinear framework, the present study is dedicated to the investigation of the capabilities of fixed- and free-interface reduction strategies to handle accurately such problems through a realistic 2D model and complements former results involving a direct modal projection with respective strong kinematic restrictions. The equations of motion are solved using an explicit time integration scheme together with the Lagrange multiplier method where friction is accounted for. The presented work discusses the notions of both displacement and motion convergences and the possibility to conduct fast parameter studies with the use of relevant reduction bases. It also shows that kinematic restrictions artificially enhance the detection of modal interactions.