Effects of wavy sidewall on vortex breakdown in an enclosed cylindrical chamber with a rotating end wall

Abstract

The effects of the wavy sidewall on flow behavior in an enclosed cylindrical chamber with a rotating end wall were investigated by a numerical model based on the steady, axisymmetric Navier–Stokes equations. The wavy sidewall influences vortex breakdown by either enhancing or reducing the swirling velocity near the top axis, depending on its orientation, amplitude, and period. When the period is small, the orientation of the wavy sidewall varies the volume of the top region of the chamber, which affects the swirling velocity there, thus influencing the occurrence of vortex breakdown. The volume-variation effect is enhanced with an increase in the amplitude, while reduced with an increase in the period. Moreover, an increase in the amplitude or period increases the length of the wavy sidewall, which enhances the dissipation of the fluid angular momentum along it. Thus, the swirling velocity near the top axis region is decreased and vortex breakdown is delayed. The resultant effect of the wavy sidewall is determined by the competition/cooperation of the volume-variation effect and the dissipation effect. However, if the period is large, the dissipation effect becomes dominant and the orientation of the wavy sidewall becomes unimportant.