Simulations of co-axial jet flows on graphics processing units: the flow and noise analysis

Abstract

Large-eddy simulations (LES) are performed for a range of perfectly expanded co-axial jet cases corresponding to conditions of the computation of coaxial jet noise (CoJeN) experiment by QinetiQ. In all simulations, the high-resolution Compact Accurately Boundary-Adjusting high-REsolution Technique (CABARET) is used for solving the Navier–Stokes equations on unstructured meshes. The Ffowcs Williams–Hawkings method based on the penetrable integral surfaces is applied for far-field noise predictions. To correctly model the turbulent flow downstream of the complex nozzle that includes a central body, a wall modelled LES approach is implemented together with a turbulent inflow condition based on synthetic turbulence. All models are run on graphics processing units to enable a considerable reduction of the flow solution time in comparison with the conventional LES. The flow and noise solutions are validated against the experimental data available with 1–2 dB accuracy being reported for noise spectra predictions on the fine grid. To analyse the structure of effective noise sources of the jets, the covariance of turbulent fluctuating Reynolds stresses is computed and their characteristic scales are analysed in the context of the generalized acoustic analogy jet noise models. Motivated by self-similarity of single-stream axi-symmetric jet flows, a suitable non-dimensionalization of the effective jet noise sources of the CoJeN jets is tested, and its implications for low-order jet noise models are discussed. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

Propulsive jet aerodynamics and aeroacoustics

“…Figure 38 shows velocity and turbulence profiles reported in Ref. 58 to 120 • , revealing accuracy within 1dB and good reproduction of the trend of measured data. This is a powerful demonstration of how LES could be used to inform designers of these trends rather than rig tests.…”

“…Promising ideas are starting to appear, including spectral broadening [53], the APE approach [52] and numerical methods making use of GPUs [58] to make long simulation times affordable. The propagation technique adopted in Refs 46, 67 also indicates better high-frequency performance.…”

“…These results imply that the quality of LES predictions seen in the single jet case is retained for coaxial jets. However, it is worthwhile to consider a second LES/FWH study of the CoJeN test case, by Markesteijn et al [58], whose method differs from others in two ways. Firstly, the numerical basis of the flow solver (the CABARET method) is fundamentally different, adopting a 'compact formulation of a 2 nd -order upwind leapfrog scheme'.…”

Jet Installation Noise Modelling Informed by GPU LES

“…The solver utilizes a GPU-optimized method for solving the hyperbolic part of the Navier-Stokes equations using the asynchronous time stepping at the optimal CFL number corresponding to a minimum dispersion and dissipation error [17,19]. The CABARET method for jet flow and noise calculations was validated in [20][21][22][23] and for airfoil flows in [24,25].…”

Advances in aeroacoustics research: recent developments and perspectives

“…Modelling here is based on a general commercial computational fluid dynamics solver (Star CCM+), which makes results of this work accessible to a wide audience in industry and academia where this software is used. The Issue concludes with the contribution by Markesteijn & Karabasov [11], which showcases advantages of using state-of-the-art computer architecture such as graphics processing units for short-turn-around-time flow and noise calculations of co-axial jets at high fidelity. The simulations are based on wall-modelled LES approach with a synthetic turbulence inflow condition and the CABARET (Compact Accurately Boundary-Adjusting high-REsolution Technique) space-time scheme for solving the Navier-Stokes equations on locally refined unstructured meshes with asynchronous time stepping.…”