Structure of high frequency Green's function in non-axi-symmetric (chevron-type) transversely sheared mean flows using a Ray tracing solver within the generalized acoustic analogy formulation

The chevron nozzle continues to remain a popular approach to reducing jet noise, which works by breaking up the turbulence structures at all scales. As indicated in Figure 1, high frequency sound waves are produced by the fine-scale turbulence structures and are emitted at a larger angle from the jet axis than low frequency waves meaning they are the greatest risk to health for airfield employees.

High frequency noise can be studied using ray theory, and here a previously developed high frequency ray tracing approach was applied to the case of a chevron with multiple lobes. The aim was to numerically evaluate the scaled Green’s function to see how it was affected by increasing the number of lobes, and see how this could reduce jet noise.