Large-Eddy Simulation of Supersonic Round Jets at High Reynolds Number

We present results from large-eddy simulations (LES) of supersonic round jets at a centerline Mach number of 1.5 using high-order compact finite-difference schemes along with an explicit filtering-based LES framework based on approximate deconvolution. The numerical method employs a sixth-order compact central differencing scheme for spatial discretization, third-order Runge-Kutta time integration. To assess the influence of the pipe at the inflow on the jet evolution, simulations are carried out for three configurations: (i) a perefectly expanded jet with an inflow pipe, (ii) a mildly over-expanded jet with an inflow pipe, and (iii) a perefectly expanded jet without an inflow pipe. The first two cases correspond to a Reynolds number (based on the jet diameter) of 𝑅_D = 10⁵ , while the third case is at a Reynolds number of 𝑅_D = 5𝑋10⁵ .

The results indicate that the presence of a pipe at the inflow has a significant influence on the jet development close to the inflow and on the subsequent downstream evolution of the jet. Instantaneous pressure contours reveal that stronger acoustic waves are generated in the mildly overexpanded case. In the mildly overexpanded jet, the supersonic core length exhibits a slight increase, accompanied by reductions in both the jet spreading rate and centerline velocity decay rate. Moreover, the mean centerline axial velocity profile demonstrates that the supersonic core length is longer in the fully expanded case without the pipe compared to the case with the pipe, suggesting that the pipe at the inflow promotes earlier jet development. Axial Reynolds stress profiles further show that the fully expanded jets, with and without the inflow pipe, display nearly comparable turbulence levels in the shear layer, whereas the overexpanded case shows lower axial Reynolds stress.