Assessment of jet inflow conditions on the development of supersonic jet flows

TL;DR

This work tackles how nozzle-exit inflow conditions shape the development of a freely propagating supersonic jet ($M=1.4$, $Re \, (based\, on\, D_j) = 1.58 \times 10^6$) by employing large-eddy simulations with a nodal discontinuous Galerkin solver. It systematically compares inviscid, steady viscous, and unsteady viscous inflows, demonstrating that including boundary-layer effects at the inlet appreciably alters near-field development and reduces peak velocity fluctuations by about 10%, while downstream flow statistics converge across inflow types. A comprehensive, openly available high-fidelity database of six LES cases is published (Zenodo), enabling validation, data-driven modeling, and further studies of inflow impact on jet dynamics. Overall, the results validate the numerical approach against experimental and prior numerical data, show limited influence of inflow on spectral distributions within the accessible Strouhal range, and provide actionable insights for inflow modeling in high-fidelity jet simulations.

Abstract

In the present work, large-eddy simulations of free supersonic jet flows are performed to investigate the influence of inflow conditions on the jet flow field and its turbulent properties. A high-order nodal discontinuous Galerkin method is employed to solve the governing equations on the generated mesh. Three different inflow profiles are evaluated to represent the nozzle-exit conditions, namely, inviscid, steady viscous, and unsteady viscous profiles. Velocity and shear stress tensor component profiles obtained from the simulations are compared with experimental data. Among the investigated profiles, the steady viscous inflow shows the most significant deviation from the inviscid case, particularly in the near-field region of the jet inlet. The steady viscous profile also leads to reduced peak velocity fluctuations, showing better agreement with experimental results. Further downstream, the influence of the inflow condition diminishes, with all three profiles converging toward the experimental reference. In addition, power spectral density analyses of streamwise velocity fluctuations reveal that the inflow conditions have little effect on spectral distributions, with numerical results showing consistent agreement with experimental data within the accessible Strouhal range. Beyond these findings, the study provides a highly detailed, high-fidelity database of supersonic jet flow simulations, encompassing six large-eddy computations with different meshes, polynomial refinements, and inflow conditions. The database includes high-frequency data in relevant regions of the jet flow field and is openly available in the Zenodo repository, ensuring accessibility and reusability for the scientific community.

Figures (18)

• Figure 1: 2-D schematic representation of the computational domain employed for the jet flow simulation.
• Figure 2: 2-D $xr$-plane cut from the numerical mesh representing the multiblock structure and the mesh generated.
• Figure 3: Details from the inlet section of the numerical mesh.
• Figure 4: Mesh cell size distributions at two longitudinal positions, $x/D_j=0.0$ and $x/D_j=15.0$, and one radial position, $r/D_j=0.0$.
• Figure 5: 2-D schematic representation and cut plane of the grid used for the RANS calculation of the nozzle flow.