International Journal of Fluid Dynamics (2000), Vol. 4, Article 1

Three-Dimensional Vortices of a Spatially Developing Plane Jet

SING HON LO

School of Mechanical, Aeronautical and Production Engineering,
Kingston University, Roehampton Vale, Friars Avenue, London SW15 3DW, U.K.

PETER RYAL VOKE

School of Mechanical and Materials Engineering,
The University of Surrey, Guildford GU2 5XH, U.K.

NICOLE JACQUELINE ROCKLIFF

School of Mechanical and Materials Engineering,
The University of Surrey, Guildford GU2 5XH, U.K.

(First Received 5th May 1999; and in revised form 28th February 2000. Published 1st March 2000)


Abstract

The coherent eddy structures of a plane jet have been investigated by using large-eddy simulation of the incompressible Navier-Stokes equations. The simulation data is presented in an animated form in three plan views that can be studied to follow the evolution of the structures. Without forced periodic excitation, the instability of the jet and transition to turbulence are characterised by the rolling up of anti-symmetric spanwise rollers. The results clearly show the formation of horseshoe-like streamwise vortex pairs and longitudinal ribs through three-dimensional instabilities of the spanwise rolls. The streamwise vortex pairs align at an angle of approximately 135 degrees (or 45 degrees) to the mean flow. The two vortex cores are connected by a thin vorticity layer and the wavelength of the spanwise perturbation is 0.51 of the distance between successive rollers. Conceptual models for the vortical structures are proposed based on the animated flow visualisation.


Keywords

Copyright Notice


Abstract

Next Section: Introduction

2. Methods

3. Results and Discussion

4. Conclusion

Acknowledgments

References