Influence of Nozzle Geometry on Jet mixing and Jet Installation Noise

Jet installation with chevron nozzles beneath a wing significantly modifies jet noise at low frequencies, and its physical mechanism must be understood to develop efficient noise reduction solutions. A numerical investigation on the jet-installation noise with an SMC006 chevron nozzle is performed byWall Modelled Large Eddy Simulation (WMLES) using the high-resolution CABARET method, accelerated on Graphics Processing Units. To simulate the jet installation, an SMC006 chevron nozzle with a penetration length of 20 degrees and length L is put at 2Dj vertically above the flat plate, resulting in a rise in noise levels at low frequency. The low frequency amplification is associated with the scattering of the near-field hydrodynamic pressure waves at the trailing edge. The numerical simulation for the baseline chevron is validated with the experiments performed at the University of Bristol. The properties of jet-hydrodynamic pressure variations and their effect on a nozzle type at Mach = 0.5 is investigated. In order
to understand the influence of chevron’s geometry on jet installation noise, the Radial Basis Function algorithm is employed to modify the penetration length and angle of the baseline chevron nozzle from 5 degrees to 35 degrees, and chevron length from 0.5L to 1.5L. It is found that the chevron’s penetration angle has a strong influence on the hydrodynamic pressure field in comparison with penetration length. In addition, a hybrid semi-analytical hydrodynamic-edge
scattering prediction model is implemented following the model of Lyu and Dowling [1] to analyse jet-installation noise for a modified chevron, using inputs obtained from individual LES simulations. The implemented model captures correct physics for the baseline nozzle and shows noise reduction of 1-2dB at peak Strouhal number for low penetration angle chevrons.