Investigation of Aeroacoustics and In-flight Particle Transport in Thermal Spray Supersonic Jets

TL;DR

This study develops and calibrates analytical and numerical models to understand how operating conditions influence aeroacoustics and particle transport in thermal spray supersonic jets, enabling non-intrusive process monitoring.

Contribution

It introduces a combined analytical and numerical framework to predict aeroacoustic signatures and particle transport in thermal spray jets under various operating conditions.

Findings

Models accurately predict acoustic levels and spectra shifts with operating conditions.

Simulations reveal jet unsteadiness and mixing influence acoustic signatures.

Aeroacoustic signatures can serve as non-intrusive process monitoring tools.

Abstract

The acoustic signature of thermal spray processes is known to vary with changes in operating conditions, which also influence particle in-flight velocity and distribution. Building on this idea, the present work first develops an analytical model that links chamber and nozzle parameters to far-field acoustic levels using gas-dynamics relations and simplified acoustic power propagation. The model is then calibrated to reduce systematic error associated with neglected turbulence effects and to improve agreement across operating conditions. In addition, a numerical framework is implemented to complement the analytical model and to resolve supersonic jet flow and in-flight particle transport. The second part of the study uses unsteady compressible simulations with hybrid turbulence modeling such as Unsteady Reynolds-Averaged Navier-Stokes (URANS) and Delayed Detached Eddy Simulation (DDES) to capture the development of the shock-containing jet and the associated near-field pressure fluctuations. Far-field sound is predicted using the Ffowcs Williams-Hawkings acoustic analogy, while a Lagrangian approach tracks particles injected at the nozzle exit to quantify velocity evolution, radial spreading, and downstream flux distributions. The influence of operating conditions (e.g., chamber pressure and temperature) is assessed, and predictions are evaluated against published microphone spectra and particle flux measurements. Overall, the combined analytical and numerical approach captures how changes in nozzle operating conditions affect jet unsteadiness and mixing, leading to measurable shifts in acoustic level and spectral content. These results suggest that aeroacoustic signatures could be used as a non-intrusive pathway to monitor and potentially control thermal spray operating conditions.