Large Eddy Simulation of an Initially-Confined Triangular Oscillating Jet

This paper reports the first large eddy simulation (LES) of a self-excited oscillating triangular jet (OTJ) issuing from a fluidic nozzle that consists of a small triangular orifice inlet followed by a large circular chamber and an orifice outlet. The case simulated is identical to that measured experimentally by England et al. (Exp Fluids 48(1):69–80, 2010). The present prediction agrees well with the previous measurement. The simulation reveals that the central oscillating jet exhibits axis-switching in the cross-section and rotates by 60° approximately over a downstream distance of x = 0.5D (chamber diameter). Three strong longitudinal vortices occur associated with the three vertices of the inlet triangle. These vortices strongly interact with the central jet and also the surroundings, in the region at x/D ≤ 1, and appear to merge finally with the outer secondary swirling flow. These observations are consistent with the deduction from previous experiments.