Nonlinear axisymmetric and three-dimensional vorticity dynamics in a swirling jet model

被引:20
作者
Martin, JE
Meiburg, E
机构
[1] UNIV SO CALIF, DEPT AEROSP ENGN, LOS ANGELES, CA 90089 USA
[2] CHRISTOPHER NEWPORT UNIV, DEPT MATH, NEWPORT NEWS, VA 23606 USA
关键词
D O I
10.1063/1.868971
中图分类号
O3 [力学];
学科分类号
08 ; 0801 ;
摘要
The mechanisms of vorticity concentration, reorientation, and stretching are investigated in a simplified swirling jet model, consisting of a line vortex along the jet axis surrounded by a jet shear layer with both azimuthal and streamwise vorticity. Inviscid three-dimensional vortex dynamics simulations demonstrate the nonlinear interaction and competition between a centrifugal instability and Kelvin-Helmholtz instabilities feeding on both components of the base flow vorticity. Under axisymmetric flow conditions, it is found that the swirl leads to the emergence of counter-rotating vortex rings, whose circulation, in the absence of viscosity, can grow without bounds. Scaling laws are provided for the growth of these rings, which trigger a pinch-off mechanism resulting in a strong decrease of the local jet diameter. In the presence of an azimuthal disturbance, the nonlinear evolution of the flow depends strongly on the initial ratio of the azimuthal and axisymmetric perturbation amplitudes. The long term dynamics of the jet can be dominated by counter-rotating vortex rings connected by braid vortices, by like-signed rings and streamwise braid vortices, or by wavy streamwise vortices alone. (C) 1996 American Institute of Physics.
引用
收藏
页码:1917 / 1928
页数:12
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