Control of Three-Dimensional Corner Separation Flow in a Highly Loaded Compressor Cascade via Dynamic Surface Deformation

Abstract

When the Reynolds (Re) number decreases below the critical value, the intensified turbulent mixing in the corner region rapidly deteriorates the performance of compressors, including efficiency and stability. However, multiscale vortices and transition processes at low Re lead to extremely complex corner flow, and it is difficult in loss control. This article explores the possibility of dynamic surface deformation (DSD) to reduce the loss in the corner region of a highly loaded compressor cascade at Re = 1.8 × 105 and 9.3 × 104. Results show that the dynamics of flapping spanwise vortex (FSV) induced by DSD are directly related to the loss control. At a high DSD oscillation frequency, FSV is unstable and rises to a higher spanwise height, which promotes the transition in the mid-span and reduces the local viscous dissipation. However, it increases the near-endwall viscous dissipation. In contrast, FSV under a low-frequency DSD inhibits transverse flow and radial migration of vortices, thus reducing the near-endwall viscous dissipation. For the single-frequency DSD, the optimal oscillation frequency of DSD matches well with the concentrated shedding vortex (CSV) characteristic frequency, reducing the viscous dissipation by 33.4%. A multifrequency DSD, superimposing the characteristic frequencies of Kelvin–Helmholtz (K–H) vortex and CSV, is superior to single-frequency DSD in terms of loss reduction, and the overall viscous dissipation is 48.6% lower than that of the uncontrolled case.