Fast and Integrated Tools for Forced Response Prediction: An Application to a Transonic Compressor Rotor Blisk

When it comes to turbomachinery, modern design trend has always been to decrease the number of stages and blade count, leading to thinner, lighter, and more loaded blades, while maintaining high efficiency and performance. This trend however may lead to mechanical issues caused by fluid-structure interaction, such as flutter and forced response. That is the reason why developing fast and highly efficient tools to properly take into account these phenomena, starting from the early design stages, is fundamental to ensure that no resonance problems occur during operation, due to the periodic nature of the aerodynamic loading. In this regard, this paper presents an integrated tool-chain for forced response assessment of bladed disks, and an application to a transonic compressor rotor blisk for validation purposes. Starting from CFD URANS simulations of a multi-stage environment, the procedure employs a dedicated in-house tool to extract the spinning pressure perturbations acting on the blade row surface, by means of a temporal and spatial Fourier decomposition. Then, a second in-house tool, integrated in the CFD framework, computes the modal work done by each rotating perturbation acting on the corresponding blade mode shape, to predict the forced response amplitude. Resulting displacement amplitude is then compared to numerical results obtained with a commercial FEM code applied to the same test-case. This method was conceived for a high integration in a CFD environment based on the URANS solver TRAF, developed at the University of Florence. The presented procedure requires as input only the blade mode-shapes of interest from FEM analysis, while aerodamping and forced response assessment are integrated in the CFD framework. The comparisons with commercial code results validate the proposed methodology highlighting the relevant saving of setup and computational time.