A turbulent jet is the chaotic flow of fluid emerging from an orifice. Jets find applications in jet cutting, jet cooling, nozzle flow, fire-fighting nozzle and atomisers. Here we investigate the effects of a diverging inlet that resembles the sub-device, “pintle”, in an airblast atomizer. The current study, when used in co-flow applications, can help avoid soot deposition on the pintle surfaces. We consider only planar jets for our study, where the mean flow is independent of the spanwise coordinate. Initially, we simulated a 2D turbulent jet flow at Reynolds number Re = 4000, based on the orifice width and the
inlet bulk mean velocity, using a RANS solver. We observed the formation of separation bubbles over the pintle surface, whose behaviour varies with changes in entrainment and turbulent intensity. For our 3D studies, we performed direct numerical simulations (DNS) using our in-house finite volume code. First, we simulated a turbulent free jet (without the pintle-shaped orifice) to investigate the choice of outflow boundary condition (BC) in the presence of entrainment. We found that the Chapman BC was a good choice for the present study. Next, we study the effects in the ‘pintle-jet’, a planar turbulent jet with the pintle-shaped orifice. We found that in the presence of a pintle-shaped orifice, the jet flaps at a much smaller frequency in the far-field region. Interestingly, we found that the near-field region, which has KH instability in the initial shear-layers, plays a major role in the far-field flow characteristics such as flapping, self-similarity and change in turbulence intensity. In addition, we observed a novel oblique vortex pattern in the case of pintle-jet. We analyzed the temporal variation of the jet characteristics
using spatio-temporal plots. In addition, the large- and small-scale turbulent motions have been studied using anisotropic invariant maps. We further consider the effects of the chamfering angle (α), which is the angle between the diverging pintle-wall and the jet centerline. Instantaneous flow fields show the large-scale flapping phenomena of jets and how the obliqueness of spanwise structures depends on α. As α decreases, there is intense flapping and high turbulence intensity in the far-field, along with the presence of less coherent Kelvin-Helmholtz (KH) vortices in the near-field. The vortex dynamics are studied, and the effects of α on the onset of large-scale motions are also investigated.