Interaction between surge and rotating stall in an axial flow compressor was investigated from the viewpoint of an unsteady inner flow structure. The aim of this study was to unravel the mechanism of the interaction between the surge and rotating stall, and unsteady behavior under the coexisting phenomena. The main feature of the tested compressor is a shock tube connected in series to the compressor outlet through a diaphragm, slits, and a concentric duplex pipe. The unsteady characteristics and the internal flow…