Resolvent-based modeling of turbulent jet noise

TL;DR

This paper develops a resolvent-based acoustic model for turbulent jet noise, demonstrating that a single mode can accurately predict the dominant noise features across different jet conditions.

Contribution

It formulates resolvent analysis as an acoustic analogy and shows that a rank-1 model can closely match LES-derived jet noise data.

Findings

A single resolvent mode captures the most energetic acoustic regions.

The rank-1 model agrees within 2dB of peak noise for both jets.

The approach effectively links near-field forcing to far-field pressure.

Abstract

Resolvent analysis has demonstrated encouraging results for modeling coherent structures in jets when compared against their data-educed counterparts from high-fidelity large-eddy simulations (LES). We formulate resolvent analysis as an acoustic analogy that relates the near-field resolvent forcing to the near- and far-field pressure. We use an LES database of round, isothermal, Mach 0.9 and 1.5 jets to produce an ensemble of realizations for the acoustic field that we project onto a limited set of resolvent modes. In the near-field, we perform projections on a restricted acoustic output domain, $r/D = [5,6]$, while the far-field projections are performed on a Kirchhoff surface comprising a 100-diameter arc centered at the nozzle. This allows the LES realizations to be expressed in the resolvent basis via a data-deduced, low-rank, cross-spectral density matrix. We find that a single resolvent mode reconstructs the most energetic regions of the acoustic field across Strouhal numbers, $St = [0-1]$, and azimuthal wavenumbers, $m=[0,2]$. Finally, we present a simple function that results in a rank-1 resolvent model agreeing within 2dB of the peak noise for both jets.