To explore the flow pattern under conditions of high altitude low Reynolds number in transonic compressor

simulation for NASA Rotor37 was conducted to probe for its vortex structure in secondary flow at high altitude condition. The study finds that the pressure side branch of horseshoe vortex induces a small-scale vortex located on the pressure side corner area near hub

corner vortex form a two-stage vortex with downstream and upstream directions

shedding vortex is developed from blade root and shed from the trailing edge

and leakage vortex near stall point only partially rupture

not as the main reason for the instability. Channel shock waves induce two radial vortexes near suction side and pressure side

the pressure side radial vortex forms a closed bubble separation

suction side radial vortex crash in blade tip passage and induce separation vortex

triggering compressor's instability under low Reynolds number. Vortex structure is consisted of horseshoe vortex

corner vortex

radial vortex

leakage vortex

separation vortex

shedding vortex and other small-scale vortexes.