Direct numerical simulation of the global transition in laminar low-density axisymmetric jets

We report a numerical study of the dynamics of laminar axisymmetric jets emerging from an injector of circular cross-section into a quiescent ambient of a heavier fluid. We focus on the critical conditions for the onset of self-sustained oscillations that characterize these jets, which are known to result from a supercritical Hopf bifurcation to a globally unstable flow. Our study aims to shed light on the discrepancies between experimental observations and predictions of linear stability theory. To this end, the unsteady Navier–Stokes equations have been solved using the finite element solver FreeFEM++, starting from a steady solution as the initial condition. The critical conditions for the onset of global instability reported in this paper lie between the experimentally observed values of Hallberg and Strykowski (2006), and those predicted by the global linear stability analysis of Coenen et al. (2017).

Direct numerical simulation of the global transition in laminar low-density axisymmetric jets Articles