Nonlinear Dynamics of Low Reynolds Number Round Jets: Periodic Attractors and Transition to Chaos

Abstract

Direct numerical simulations have been shown [1, 2] to provide detailed information on the dynamics and coherent structures of the near field of a spatially developing axisymmetric jet. In [1] we demonstrated the shift from helical to axisymmetric structures with increasing diametral Reynolds number in the range [200; 500]. At the upper bound of this range, the varicose m = 0 mode is the most amplified (m is the azimuthal wave—number). The development of the unsteady flow is accompanied by the well known phenomena: 2D Kelvin—Helmholtz instability, roll-up and pairing, stream—wise filaments and side—jets. The onset of the asymptotic chaotic state is preceded by vortex rings reconnection and breakdown of the large structures due to strong stream—wise filaments. A similar transition process was observed in temporal simulations by Melander et al. [3].