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Direct and indirect noise generated by injected entropic and compositional inhomogeneities

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Conference Object

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Rolland, EO 
De Domenico, F 


Flow disturbances are generated inside a duct via pulsed injection of helium into a flow of air. This leads to the generation of an acoustic pulse (direct noise), as well as the production of entropic and compositional inhomogeneities which are convected with the mean flow. As these inhomogeneities are convected through a choked nozzle, they generate indirect noise. The resulting acoustic pressure fluctuations are measured experimentally using pressure transducers upstream of the nozzle. Insight obtained from theoretical models and a time-delay analysis can be used to isolate and extract the contributions of direct and indirect noise in the experimental signal. These results are directly compared to existing one-dimensional direct and indirect noise models. The experimental measurement of indirect noise is found to be in good agreement with the theoretical models for entropy noise and compositional noise for a compact one-dimensional isentropic nozzles.



4012 Fluid Mechanics and Thermal Engineering, 4007 Control Engineering, Mechatronics and Robotics, 40 Engineering

Journal Title

Proceedings of ASME 2017 Turbomachinery Technical Conference & Exposition GT2017 June 26-30, 2017, Charlotte, USA

Conference Name

ASME 2017 Turbomachinery Technical Conference & Exposition

Journal ISSN

Volume Title

Volume 2C: Turbomachinery


American Sociery of Mechanical Engineers
This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) grant EP/K02924X/1. Erwan Rolland is supported by an EPSRC DTA studentship (University of Cambridge), Francesca De Domenico is supported by the Honorary Vice-Chancellor’s Award and a Qualcomm / DTA Studentship (University of Cambridge).