Guide Vane Vibrations Caused by Wakes and Blower Noise—Part 1: The Vortex Degeneration in the Asymmetrical Wakes

The symmetrical wakes beyond a guide vane cascade consisting of curved and flat plates with blunt trailing edges were investigated as far as the excited dynamic stresses in the blades and the vortex Strouhal number are concerned. The results reveal that the flat plate is more liable to be damaged by the Karman vortex street than the curved plate. However, the vortex street can be effectively suppressed by giving the trailing edge an asymmetrical form. It will be shown that this suppression orginates from the difference of the vortex strengths in the two rows of the vortex street, causing the rapid degeneration of the vortices. This leads to the suppression of the reinforcement of the vortex strength by the lock-in because of lack of stable vortex region.