Steady axisymmetric flow in an enclosed conical frustum chamber with a rotating bottom wall

Abstract

The swirling flow in an enclosed conical frustum chamber with a rotating bottom wall was studied by a numerical model based on the steady, axisymmetric Navier–Stokes equations. The flow behavior was investigated over a wide range of parameters, that is, the Reynolds number up to 2500, the aspect ratio up to 3.5, and the slope angle of the sidewall from 60° to 180°. The vortex breakdown boundary curves were summarized. It was found that vortex breakdown is delayed or even suppressed in the convergent chamber (chamber section narrowing upward). However, for the divergent chamber, the onset of vortex breakdown is precipitated by an initial increase in the slope angle while delayed by a further increase in the slope angle. The flow separation along the inclined sidewall may occur in the divergent chamber with a big slope angle. For an even bigger slope angle, this separation bubble directly combined with the corner vortex at the upper right corner, forming a large recirculation region. The present results suggested that, although vortex breakdown can occur in the divergent chamber with any slope angle, it cannot occur in a convergent chamber with a small slope angle as well as in a conical chamber.