Self-similarity in Slightly Heated Annular Jet with Large Diameter Ratios
Abstract
The study aims at furthering our understanding and quantifying the influence of coherent structures on small-scale turbulence and passive scalar mixing, in an annular jet configuration with large diameter ratios. This ’bluff-body’ geometry is close to that widely used in combustion for flame stabilization [1]. A passive contaminant is introduced in the flow, through a slight heating. We report the evolution along the jet axis of the following quantities: mean values of the longitudinal velocity and passive scalar ( U¯ and Θ¯ ), as well as the energy and scalar dissipation rates ( ε¯ and χ¯ ). It is shown that these statistics: decay as x−1 and x−4 , where x is the streamwise direction, similarly to the decay in the far-field of classical jets (CJ);unlike the CJ, they reach self-similarity faster, a behaviour that may be attributed to the presence of coherent structures.