Jet Noise Receptivity to Nozzle-upstream Perturbations in Compressible Heated Jets

E ects of nozzle-upstream entropy perturbations on the acoustic radiation from heated jets are investigated. For this, a model problem is considered, in which a gas-turbine combustor discharges reaction products through a converging nozzle into the ambient environment. The turbulent reacting ow eld in the combustor is computed using large-eddy simulation (LES), and the unsteady oweld at the combustor exit is extracted to provide realistic in ow conditions to the jetow simulation. To study the indirect coupling process, arising from the interaction of the combustion-generated entropy uctuations with the adverse pressure gradient through the nozzle, a linearized Euler formulation is employed. Parametric studies are performed to investigate e ects of frequency and amplitude of the nozzle-upstream entropy perturbations on the jet instability and the jet noise directivity. Simulation results show that the directivity is dependent on the perturbation frequency. Excitation near the preferred shear-layer instability leads to strong acoustic radiation in the 45 forward direction, and the radiation angle decreases with decreasing excitation frequency.