Control of corner separation via dimpled surface for a highly loaded compressor cascade under different inlet Mach number

In this paper, flow characteristics of dimpled compressor cascades are numerically discerned by solving the compressible Reynolds-averaged Navier-Stokes equations on structured grids over the inlet Mach number ranging from 0.3 to 0.8. Four rows of parallel, spherical dimples with a depth of 0.2 mm and a depth-to-diameter ratio of 0.25 are embedded along 10%-32% and 38%-60% chord of suction surface respectively. Results showed that two dimple configurations can both reduce the total pressure loss in all researched Mach number except that of 0.8. The suppression of three-dimensional separation near the hub-corner region is the primary cause of loss reduction. What's more, the separation bubble on the suction surface can be also eliminated or depressed due to the disturbance and higher level of turbulence kinetic energy within boundary layer. According to the distribution of axial vorticity in flow passage, the dimpled vortex can also suppress the migration of secondary flow along spanwise direction under a relative higher cross pressure gradient. (C) 2018 Elsevier Masson SAS. All rights reserved.