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 (\(\bar{U}\) and \(\bar{\varTheta }\)), as well as the energy and scalar dissipation rates (\(\bar{\varepsilon }\) and \(\bar{\chi }\)). 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. Open image in new window