Numerical simulations of tornado-like vortices. Part II: Two cell vortices

摘要

The axi-symmetric numerical vortex model described in Part I is used here to study the evolution and structure of tornado-like vortices within a broad region of forcing in relation to the surface boundary constraint. It is shown that with a free-slip surface condition, a two cell vortex can occur with downflow along the axis, despite the fact that the driving force is everywhere upwards. The dynamics of such vortices is discussed and contrasted with that of single cell vortices which are preferred when a no-slip surface boundary condition is used.