Supersonic jet flow and noise simulations of military-style baseline and chevron nozzles

Numerical simulations are described for the flow and noise generated by jets with and without noise reduction devices. In particular, chevron nozzles are described. The nozzle geometries used in the simulations are characteristic of high performance low-bypass ratio turbofan engines, including the facets to represent the engine seals and flaps. The simulations use a structured multiblock grid approach with high-order dispersion relation preserving discretization in space and dual time-stepping for time advancement. The convergence of the sub-iterations is achieved with implicit residual smoothing and multigrid. Both matching and non-matching characteristics-based block interface conditions are used. A Detached Eddy Simulation turbulence model is used for the internal nozzle flow, but it is deactivated in the jet exhaust. The chevrons are simulated using an Immersed Boundary Method. The discrete form of the method is used where the residuals in the momentum equations are set to the appropriate velocity, usually zero, at grid points internal to the chevrons. The spatial resolution in the vicinity of the chevrons is increased. This is permitted through the use of the non-matching block interface condition. Predictions for the instantaneous and time-averaged flow properties are presented and comparisons are made with available experimental data. The radiated noise is predicted using the Williams - Hawkings equation solution for a permeable acoustic data surface. Both OASPL and spectral predictions are presented and comparisons are made with measurements. Noise source location studies are shown based on the polar correlation technique using the predicted noise time histories in the far field.