Rayleigh scattering for compressible flow diagnostics, principles and application to the study of jet noise
During take-off, the exhaust jet from a turbojet engine contributes significantly to the noise generated by the aircraft. This justifies the need for extensive research to better understand the noise generated by these flows. However, the study of jet aeroacoustics, whether numerical or experimental, presents numerous challenges and requires the development of specific methods. The presentation will focus on an original experimental technique to measure the local density of a flow in a time-resolved and non-intrusive manner. The technique is based on Rayleigh scattering, which is the scattering of an electromagnetic wave by small particles. In the present context, the wave is laser light and the particles are the constituent molecules of the gas, mostly N2 and O2. This means that there are no non-intrinsic tracers already in the flow, making this method particularly well suited to fast moving flows. Within this framework, the intensity of the scattered light can be directly related to the local density of the flow.
After some context and a brief introduction of the theoretical background of the technique, we further discuss an example study in the context of jet noise, and then examine the practical implementation of such an apparatus.
Contact Nathanaël Machicoane for more information or to schedule a discussion with the seminar speaker.