Large Eddy Simulation for the Analysis of Supersonic Jet Noise Suppression Devices

Doktorsavhandling, 2010

Stricter noise regulations for commercial and military aircraft have increased interest in noise reduction techniques within the aerospace industry. To meet the requirements, new noise suppression technologies have to be developed and numerical methods need to be validated and possibly improved for the correct assessment of these technologies. In this thesis the main focus is to explore techniques to reduce the noise from the exhaust part of a typical military fighter engine. In this investigation, two techniques, which have been proven to be effective on subsonic jets, are studied. The first technique is the use of passive flow control devices, such as chevrons, for increasing the mixing rate in the shear layer of the jet. The second technique is the use of fluidic injection, through micro-jets, which have the capability to be controlled during flight to minimize thrust loss and maximize noise reduction. Large eddy simulation (LES) is used as a numerical prediction tool to predict the flow field and a Kirchhoff surface integral technique is used to extend the acoustic domain. In all cases studied, the nozzle geometry is included in the calculation domain. The numerically predicted flow field and acoustic results are compared with experimental data. The impact on flow field and acoustic signature by the different nozzle designs are evaluated. Also, the effect of forward flight is investigated at different free stream Mach numbers. Specific numerical issues when simulating supersonic jet flows and dealing with complex geometries are addressed and the applied methods are evaluated.