Self-sustained oscillations in a homogeneous-density round jet

Abstract

The paper is devoted to a new phenomenon of self-sustained oscillations triggered in a round free homogeneous-density jet. It was shown by the experimental investigations supported by the numerical approach based on extensive-Large Eddy Simulations studies that such a self-sustained regime can be established in a homogeneous-density jet, provided that the boundary layer at the nozzle exit is sufficiently thin and the perturbation level sufficiently low. The growth rate of the naturally amplified unstable modes is high enough to induce backflow leading to self-excited oscillations.

Keywords:

• round jet instability
• Kelvin–Helmholtz instability
• LES

Acknowledgements

The authors gratefully acknowledge the support of the Polish State Committee for Scientific Research through the grant nos. 7T07 C05 008 and 8 T10B 009 19. Part of the LES computations were performed within FP6 project FAR-Wake No. AST4-CT-2005-012238. Authors are grateful to Dr. L. Lesshafft and Dr. M. Juniper for discussions and valuable suggestions.