Structure of rotating stall cells. Part 2: Relative motion

The velocity was measured near the blade surface at three different chordwise and two radial positions for all operating conditions of a low speed axial flow compressor. The local flow angle increases in the streamwise direction for a given operating condition on the negative slope part of the characteristic. This flow angle varies in the unstalled region from -7 deg, 18 deg to 60 deg. Important radial flow angles are observed during one and two cell rotating stall patterns. The 25% chord location experience a radially inward flow during rotating stall, while the 50% and 75% locations show radially outward flow. This radial motion decreases near the tip and mixes with the clearance flow.