Dominating unsteadiness flow structures in corner separation under high Mach number

Corner separation is a key factor affecting the aerodynamic performance of compressors, whereas corner separation under a high-Mach-number condition is a scientific problem with practical engineering significance. Using a self-developed high-precision (Roe scheme for convective flux calculation and fifth-order weighted essentially nonoscillatory for reconstruction) delay detached-eddy simulation (DDES) code, a compressor cascade with massive corner separation under a high Mach number is simulated. The primary aim of the simulations is to obtain the dominating fluctuation vortex structures in and out of the blade passage, as well as to analyze the reason for the formation of these structures. The vortex structures are analyzed after verifying the accuracy of the code. An advanced data mining technology (that is, dynamic mode decomposition) was performed to extract the dominating fluctuation flowfield simulated by DDES for the first time. The results prove the credibility of the self-developed code. It is found that the passage vortex and the hairpin vortex are the primary sources of unsteady fluctuations in and out of the passage, respectively. The former is formed by endwall separation, and the position where it is generated is relatively stable; thus, the endwall suction technology is suggested for flow control. The latter is formed by the intermixing of the passage vortex, the trailing-edge shedding vortex, and the concentrated shedding vortex. Owing to the different frequencies of those three kinds of vortices, different hairpin scales are formed. The research results can provide a basis for flow control design.