Accurate simulation of the noise generated by a hot supersonic jet including turbulence tripping and nonlinear acoustic propagation

Abstract

A procedure to accurately simulate a free hot supersonic jet and its associated noise, which uses simultaneously a turbulence tripping method and a two-way coupling between a flow solver and a nonlinear acoustic solver, is proposed in this study. A Mach 3.1 overexpanded hot jet is computed via a large-eddy simulation by solving the filtered Navier-Stokes equations with a finite volume method on unstructured grids. The resulting noise is propagated in the far field by solving the full Euler equations with a high-order discontinuous Galerkin method on unstructured grids. The full convergent-divergent nozzle is explicitly included in the computational domain thanks to the unstructured flow solver. Both a refined grid and a geometrical boundary layer tripping in the convergent are used to get highly disturbed turbulent conditions at the nozzle lips. The flow field appears to agree with the expected turbulence behavior and the available experimental data. The jet development shows significant improvement compared to similar past simulations. The far field acoustic levels are finely recovered at most of observation angles. An analysis of the acoustic near and far fields is then performed. The studied conditions lead to strong shock-associated noise and Mach wave emission. The spatio-frequency and azimuthal content of the acoustic field is described in order to identify the main noise properties. A particular noise component, different from screech tones and radiating upstream like Mach waves, is highlighted. Nonlinear propagation effects are finally quantified through specific metrics. They are found significant in both the near and the far fields which justifies the use of a nonlinear acoustic solver.

Large-eddy simulations of the flow and acoustic fields of a rocket jet impinging on a perforated plate

“…For z ≥ 5r 0 , inclined wavefronts of strong amplitude are also seen to propagate in the downstream direction. They are typical of Mach wave radiation, as noticed in several previous simulations of free jets at Mach numbers higher than 2 [25][26][27][28]. These waves are produced by the convection of turbulent coherent structures at a supersonic speed.…”

Modelling of jet noise: a perspective from large-eddy simulations

“…The Ffowcs Williams-Hawkings (FW-H) equation [48] is one of the most commonly used hybrid methods. More complex models for wave propagation, such as linearized Euler equations (LEE) [15] or their full nonlinear version [49], can also be integrated numerically for near-field acoustics. When the acoustic field is intense, as in sonic boom propagation [21], or in crackle emission from hot supersonic jets, discussed in § §3b, the nonlinear effects are important.…”

Coupled CFD-CAA Simulation of the Noise Generated by a Hot Supersonic Jet Impinging on a Flat Plate with Exhaust Hole

“…In the "Main" domain, turbulence is geometrically triggered thanks to the introduction of a small step in the nozzle convergent [17,18]. Several refinement zones are applied at different locations.…”

“…Considering that the flow near the nozzle exit is not perturbed by the plate, i.e. while x/D j < 10, the comparison of axial profiles near the nozzle exit with experimental data and previous numerical results on the free jet configuration [10,18] is performed. It will allow the validation of the used turbulence triggering method and of the grid construction strategy adopted in order to preserve perturbations downstream.…”

“…Indeed, a low initial turbulence level is known to cause a delayed and steeper transition of the laminar shear layer, inducing a shorter potential core, vortex pairings and an overestimation of near and far-field acoustic levels [17]. The grid from study [10] is 62 million cells without turbulence triggering, while the grid from study [18] is nearly 200 million cells with turbulence triggering. The grid in this study has been optimized from the first grid, accounts 75 million cells and turbulence is triggered.…”