This geometry is a NASA low-speed centrifugal compressor. The objective of the project was to assess the flutter risk (self-excited and self-sustained aeroelastic instability) that could lead to fatigue and/or damage of the blades.
The computational cost for flutter prediction can often be prohibitive at the design stage, and efficient fluid-structure interactions tools are required. For this project, the Modal Approach coupled with NLH (non-linear harmonic) method, implemented in FINETM/Turbo software from NUMECA, was used. The advantage was that only one blade channel was needed whatever the inter-blade phase angle.
The structural mode shapes were provided to the solver as a pre-processing step. Then, the non-linear harmonic calculation was run, providing the harmonic blade displacements. The unsteady flow response could then be reconstructed. The picture above presents the magnitude of the blade deformation, as a function of time, around the steady deformed shape. The aerodynamic damping, derived from the unsteady flow response, could be analyzed for the different inter-blade phase angles and stability could be assessed.