Analysis of noise from a transcritical N₂ jet using a hybrid CFD/CAA solver for simulating real fluid flows

Fuel combustion under transcritical conditions in high-pressure combustors offers high thermal efficiency but is also accompanied by loud noise, which has the potential to trigger thermo-acoustic instabilities that can damage the combustor. As a first step toward understanding noise from real fluid flows under such severe conditions, a non-reacting N₂ jet under transcritical conditions is simulated in this work. A hybrid Computational Fluid Dynamics (CFD)/Computational Aero-Acoustics (CAA) solver developed for simulating real fluid flows and the noise radiated by them is demonstrated and used to analyze the generation and radiation of noise from this transcritical N₂ jet. In this hybrid simulation, the turbulent flow field of the jet is predicted using Large-Eddy Simulation (LES) which employs an efficient and robust pressure-based semi-implicit algorithm tailored for compressible real fluid flows (i.e., the CFD simulation), and the LES results are validated against experimental data. To describe the generation and radiation of noise from this N₂ jet, the Linearized Euler Equations (LEE) reformulated to consider real fluid effects are solved in the CAA simulation. Source terms of the LEE are computed from the solution of the LES which offers a spatiotemporal description of the noise-generating sources. Then, to characterize the far-field noise radiation, the acoustic field predicted by the LEE solver is analyzed in terms of sound pressure amplitudes, spectral content, and directivity behavior.