Numerical simulations of sound radiated from an axisymmetric premixed reacting jet

The sound radiated by an axisymmetric (two-dimensional) premixed reacting f ree jet was studied using direct numerical simulation. The jet was injected into cold combustion products. A narrow (in radial extent) high temperatur e pulse was specified at the jet inlet to stabilize the reacting jet. The c omputational domain included both the near-field flow and far-field acousti c regions. Both reacting and nonreacting cases were considered. The heat re lease associated with the reacting jet had a significant effect on the vort ical structure, as well as the sound radiation level and pattern, within th e jet. The sound radiation pattern and the source terms in Lighthill's equa tion were used to identify apparent sound source locations. Within the cont ext of the assumptions of the present simulations, the results showed that the effect of heat release was to: (1) Stabilize the jet, (2) enhance sound radiation levels due to an increase in the entropy source, and (3) shift t he frequency of the most unstable mode to lower values, resulting in a broa der sound spectrum. (C) 2001 American Institute of Physics.