This paper presents flow visualizations of the unsteady flow field near the endwall of a compressor cascade. The experiments were performed in a water tunnel using the hydrogen bubble technique. A Pt wire was positioned parallel to the endwall and ahead of the cascade at 2% span from the endwall. The traces of hydrogen bubbles generated by the wire were visualized within a light sheet arranged at various cross-sections around the cascade. The unsteady flow field was visualized at different incidences without a radial clearance. A periodically fluctuating horseshoe vortex system of varying number of vortices is observed near the leading edge of the cascade, which plays a leading role in the flow field near the endwall. The interaction and the flow mixing among the counter-rotating horseshoe legs, the endwall boundary layer and the main flow, periodically occur in the passage. Breakdown of the horseshoe vortex is clearly observed in the cascade while the unsteady and complex flow field is shown at the corner of the suction surface.

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