Numerical Study on the Corner Separation Control for a Compressor Cascade via Bionic Herringbone Riblets

Abstract

Bionic herringbone riblets are applied to relieve the flow near the blade endwall in a linear compressor cascade under the incidence angle of −4° to 6° at a Reynolds number of 382,000. The herringbone riblets are placed at the endwall upstream of the blade, and the Reynolds-averaged Navier–Stokes simulations are performed to explore their effects on corner separation and the control mechanism. The results show that the herringbone riblets can effectively improve the corner separation over the stable operating range, and the control effect is affected by the riblet height and the yaw angle. The implementation of herringbone riblets with a height of only 0.08 boundary layer thickness and a yaw angle of 30 degrees can reduce the total pressure loss by up to 9.89% and increase the static pressure coefficient by 12.27%. Flow details indicate that small-scale vortices in the riblet channels can accumulate and form a high-intensity large-scale vortex close to the bottom of the boundary layer downstream. Compared with traditional vortex generators, the herringbone riblets induce a vortex closer to the wall due to their smaller size, which can reduce the damage of an induced vortex to the mainstream and enhance its control over the bottom of the boundary layer, thereby effectively reducing additional losses. The induced vortex enhances mixing and injects kinetic energy into the low-energy fluid, thus inhibiting the transverse migration of low-energy fluid in the endwall boundary layer, delaying the formation of the separating vortex, further suppressing the development of corner separation and improving the aerodynamic performance of the cascade.