A Framework and Approach for Leveraging Unsteady Response in Turbocompressor Flowfields

Abstract Based on the thesis that critical destabilizing flow structures exhibit coherent response to periodic excitation and can be usefully organized via tuned periodic forcing, the work presented herein emphasizes the dynamical behavior of a representative compressor flowfield under periodic transients and the difficulty in extracting useful information on flowfield response in the poststall regime. The paper begins by developing a surrogate model to understand the onset of rotating stall. This model takes the form of a two-dimensional (2D) linear cascade, which serves as a simplified representation of essential turbocompressor flow dynamics. Steady and unsteady Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) modeling is conducted on both single and multi-passage domains. This analysis aims to highlight the advantages and limitations of domainperiodic extent, providing insights into the behavior of the compressor flow under different conditions. The research evaluates both established and developing rotating stall phenomena from a passage control volume perspective. This approach helps identify dynamical traits and underlying flowfield features that contribute to stall inception and development. Stability analysis and resolvent analysis techniques are applied to the surrogate compressor flowfield to understand the causes of instability onset and potential mechanisms for controlling spike-type stall inception structures. These analyses provide valuable insights into the dynamics of rotating stall and strategies for managing its effects. The paper concludes by demonstrating an example approach for managing rotating stall, showing promising results for improving flowfield robustness to destabilizing perturbations. This approach involves the implementation of tailored periodic forcing to mitigate the effects of stall and enhance compressor usable work transfer.