DOI: 10.1615/TSFP2
THE IRREGULAR VORTEX SHEDDING REGIME FOR A SQUARE CYLINDER WAKE NEAR A WALL
RÉSUMÉ
Surface pressure and wake velocity fluctuations are used to investigate the changes in vortex shedding from a square cylinder near a solid wall for Reynolds number 18,600. Time and frequency analyses show that the formation of shed vortices occurs further downstream of the cylinder as the critical gap height for suppression is approached. Permanent reattachment of the shear layer on the lower cylinder face interrupts the feedback mechanism between the wake and cylinder side face and periodic fluctuations can only be detected downstream of the cylinder. Complete suppression of vortex shedding occurs as the gap height is further reduced. The combined influence of gap blockage and reduced streamline curvature causes a reduction in the ratio of the lower to upper shear layer intensity below the critical value for the stable vortex street formation predicted from stability analysis.