Published online by Cambridge University Press: 26 April 2006
It is shown that certain similarity solutions relating to axisymmetric vortices in a viscous fluid over a plane wall can be associated with a point source or sink of vorticity at the origin and a line vortex along the symmetry axis of the system. The rotationality of the nonlinear terms in the momentum equation, due to the radial vorticity and the azimuthal flow field, induces a poloidal flow which relates to one-cell or two-cell configurations. It is shown that a small imput of radial vorticity into a strong line vortex can induce an intense up-draught. There are ranges of values of the parameters yielding two solutions. The extremeties of these ranges are associated with values that yield velocity breakdown.