Experimental investigations into vortex flow in a straight,annular section channel

Results of experimental velocity measurements in air at several cross-sections along a straight annular section channel comparable to a hydraulic machine admission duct are presented. The flow analysis focuses on the axial and tangential velocity components and their modification with changes in the intensity of swirl along the channel. Particular prominence is given to an anomalous flow, the ‘dead water core’, occurring at the greatest swirl intensities. An earlier method of evaluating the core size of this anomalous flow on the basis of a vortex-type schematization is tested; Strscheletzky's method is also analysed. Finally a definition of the dead water core dimensions based on the axial velocity component distribution is proposed