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Evolution of isolated turbulent trailing vortices Karthik Duraisamy1,a

Summary: Evolution of isolated turbulent trailing vortices
Karthik Duraisamy1,a
and Sanjiva K. Lele2,b
Department of Aerospace Engineering, University of Glasgow, Glasgow G12 8QQ, Scotland
Department of Aeronautics and Astronautics and Mechanical Engineering, Stanford University,
Stanford, California 94305, USA
Received 5 November 2007; accepted 4 January 2008; published online 3 March 2008
In this work, the temporal evolution of a low swirl-number turbulent Batchelor vortex is studied
using pseudospectral direct numerical simulations. The solution of the governing equations in the
vorticity-velocity form allows for accurate application of boundary conditions. The physics of the
evolution is investigated with an emphasis on the mechanisms that influence the transport of axial
and angular momentum. Excitation of normal mode instabilities gives rise to coherent large scale
helical structures inside the vortical core. The radial growth of these helical structures and the action
of axial shear and differential rotation results in the creation of a polarized vortex layer. This vortex
layer evolves into a series of hairpin-shaped structures that subsequently breakdown into elongated
fine scale vortices. Ultimately, the radially outward propagation of these structures results in the
relaxation of the flow towards a stable high-swirl configuration. Two conserved quantities, based on
the deviation from the laminar solution, are derived and these prove to be useful in characterizing


Source: Alonso, Juan J. - Department of Aeronautics and Astronautics, Stanford University


Collections: Engineering