Lattice-Boltzmann simulation of coaxial jet noise generation

A Lattice-Boltzmann model for high-speed non-isothermal subsonic flows is used to simulate the unsteady jet exhausting from a short-cowl axisymmetric coaxial nozzle and the associated noise. The primary and secondary jet exit Mach numbers are 0.87 and 0.90, respectively, the secondary jet Reynolds number is 2.8 · 10, and the primary to secondary temperature ratio is 2.7. The far-field is computed through a Ffowcs-Williams and Hawkings analogy applied to a fluid surface encompassing the plume. Numerical results are presented for one exhaust condition and for one grid resolution only; in this respect, the main achievements of the present effort are a sanity check of the simulation setup and a first stage of a grid resolution study. The presented nearand far-field results confirm that the underlying flow features are reasonably represented by the numerical solution. Areas of required improvements have been clearly identified in the growth rate of the shear-layer turbulent fluctuations and will be the main objective of future studies. More in general, the sensitivity of the jet turbulent properties to the mesh resolution will be investigated and published in the future as a completing part of the present work.