A study of similarity solutions for laminar swirling axisymmetric flows with both buoyancy and initial momentum flux

Using an asymptotic approach, the established similarity solution for a plume is extended to the case of a plume with a small amount of angular momentum flux. Numerical simulations of laminar flows are performed in order to verify the similarity solution and to further examine the behavior of plumes with and without swirl and to compare with those of jets and swirling jets. Vortex breakdown of jets and plumes is explored, and an analytical estimate for the critical swirl in plumes is obtained, which compares well with the simulation results. A comparison is made between vortex breakdown in jets, where vortex breakdown destroys the jet-like behavior, and plumes, where vortex breakdown has a weak effect and the flow continues to have plume-like behavior. Simulation results of buoyant jets and injected plumes are presented, and the behavior of vortex breakdown of these hybrid flows is discussed in reference to the pure cases. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3658732]