Formation of Multiple Vortices in a Confined Two-Fluid Swirling Flow

This numerical study explains the formation of multiple circulation cells in a confined swirling two-fluid flow. Providing fine and nonintrusive mixing of ingredients, multiple vortices are beneficial for the growth of tissue culture in aerial bioreactors. A convenient model of bioreactor is a sealed vertical cylindrical container filled with air and liquid. Rotation of the bottom disk drives the circulation of both fluids. Our study reveals that as the rotation intensifies, at least ten circulation cells develop: six in the lower fluid and four in the upper fluid. This steady axisymmetric multi-cell flow exists in some range of the rotation speed. There arises shear-layer instability as the rotation speed significantly exceeds this range. Therefore, such multi-cell flow might have applications in bioreactors where the rotation speed must be moderate for avoidance of destruction of tissue.