An assessment of OpenFOAM solver on RANS simulations of round supersonic free jets

Numerical performance of rhoCentralFoam, a compressible solver in OpenFOAM, was studied by modeling round supersonic free jets with varying nozzle exit conditions through Reynolds-Averaged Navier-Stokes approach. To understand the behavior and accuracy of the solver, simulations were conducted at four different nozzle pressure ratios (i.e. NPR = 2.8, 3.4, 4 and 5), corresponding to over-, perfectly-, moderately under- and highly under-expanded exit conditions, respectively. The simulated results were subsequently validated against qualitative and quantitative experimental results and good overall agreements can be observed, in terms of the shock structures along the jet core as well as the mixing characteristics through velocity decay and shear layer growth. In particular, the predicted lengths of the first shock cell were within 4% of those measured from experiments. However, the jet shear layers determined from k-ω SST model showed wider spread and hence over-estimating the jet mixing behavior. Nevertheless, the discrepancies were still deemed to be within acceptable range (<10%). In addition, results obtained from comparisons with commercial CFD solver also demonstrate certain advantages in numerical accuracy for rhoCentralFoam solver, under the present simulation conditions.