Swirl effects on external intermittency in turbulent jets

In this paper we present the modelled results of velocity and mixture fraction intermittency for selected isothermal swirling jet flows using Large Eddy Simulation (LES). The modelled problems considered three different swirl numbers S = 0.3, 0.54 and 0.8 respectively. The probability density functions (pdfs) and intermittency of velocity and mixture fraction are presented. The simulations capture well complex flow features such as centre jet precession, a bluff body stabilised recirculation zone, and swirl induced vortex breakdown and also describe the effects of far field flow as well as scalar distributions. The calculated probability density distributions exhibit changes from a Gaussian to a delta function with increased radial distance from the jet centreline, and also a non-Gaussian shape on the jet centreline near the precession region. The radial variation of the intermittency shows differences between results with increased swirl number, especially inside the downstream swirl-induced recirculation region.