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Key areas of noise sources are investigated through comparison of eddy convection velocity and turbulence measurements in three-stream nozzles. A Time-Resolved Doppler Global Velocimetry (TR-DGV) Instrument was applied to the Nozzle Acoustic Test Rig (NATR) at NASA's Aero-Acoustic Propulsion Lab (AAPL) to measure convection velocity. Particle image velocimetry (PIV) measurements provided mean velocity and turbulence intensity. Eddy convection velocity results were obtained from the TR-DGV data for three-stream nozzle configurations using a cross-correlation approach. The three-stream cases included an axisymmetric and an asymmetric nozzle configuration. Results of the VT TR-DGV convection velocity were compared to NASA PIV mean and turbulence intensity data. For the axisymmetric case, areas of high convection velocity and turbulence intensity were found to be from 4 to 6 diameters downstream. Comparison of convection velocity between the axisymmetric and offset case show this same region as the greatest reduction in convection velocity due to the offset. These findings suggest this region along the centerline near the end of the potential core is an important area for noise generation with jets and contribute to the noise reductions seen from three stream offset nozzles. An analysis of a one-dimensional wavepacket model was completed to provide understanding of the effect of the various convection velocities seen in the flow. Comparison of a wavepacket with a convection velocity of 0.6Uj to a wavepacket with a convection velocity of 0.8Uj showed that an increase in convection velocity shifts the wavenumber spectrum to higher wavenumbers as expected. It was also observed that for the higher convection velocity wavepacket, higher frequencies are more acoustically efficient, while mid frequencies are the most efficient radiators in the lower convection velocity case. Using mean velocity, turbulence intensity, and convection velocity areas of likely to generate noise are identified and possible fundamental mechanisms responsible for the noise generation are discussed. / Master of Science / Noise from the jet exhaust plumes of aircraft engines continues to be a problem in the aerospace field, specifically for applications where high speeds and temperatures are required. This study works to identifity the noise producing areas in a high speed, heated jet plume for a new type of exhaust nozzle configurations. Identification of the noise producing regions will allow desing of quieter aircraft engines. Traditionally, there are two streams in the exhaust of aircraft engines. This research is a study of a new exhaust nozzle configuration with an additional third exhaust stream. Specifically, two three-stream nozzle configurations are studied: one that is symmetric and one with the third stream shifted relative to the other exhast streams which is called the offset configuration. Past studies have shown that three stream jets and offset three stream jets offer noise reductions. Of the two configurations studied, the offset configuration offers greater potential for noise reduction. The flow field of three stream jet and a three stream shifted jet are analyzed. Flow properites relating to the speed of the jet, the level of turbulence, and the speed at which flow structures convect are analyzed for the symmetric three stream nozzle. The region along the jet centerline is identified as a likely noise producing area based on analysis of the flow properties. Comparison of the three stream symmetric configuration with the three stream offset configuration shows the offset configuration reduces the convection speed of structure along the jet centerline. This reduction in convection velocity is an explanation for the noise reduction caused by the offset nozzle configuration. A simple mathematical model to describe how the flow structures convect is developed in order to better understand how the differenct convection speeds observed impact noise production. Many researchers in the past have suggested that the area of high shearing caused by the velocity difference between the jet and the surrounding is the dominant noise producing region, however, analysis of the experiemental results from this research has found the centerline region as a likely noise producing region. Results from the model, therefore, were obtained for both the high shearing region and the centerline region previously identified for both jet configurations. It was found that the region along the centerline showed a greater difference in likeliness to produce noise, further suggesting that the reigon along the centerline is important for noise production.

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