Identifying the radiating core of Lighthill’s source term |
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Authors: | Marie Cabana Véronique Fortuné Peter Jordan |
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Institution: | 1.Laboratoire d’Etudes Aérodynamiques (LEA),Université de Poitiers, ENSMA, CNRS,Poitiers Cedex,France;2.Laboratoire d’Etudes Aérodynamiques (LEA),Université de Poitiers, ENSMA, CNRS, Centre d’Etudes Aérodynamiques et Thermiques,Poitiers,France |
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Abstract: | A decomposition of the Lighthill source term is effected which yields ten sub-terms comprising velocity, vorticity, dilatation
and density fields. An analysis methodology is then developed, aimed at understanding the respective roles played by these
sub-terms in the production of sound. By Direct Numerical Simulation of a temporal mixing-layer—chosen both for its simplicity
and its amenability to analysis in wavenumber space—the radiating components of the different sub-terms are isolated and studied.
Interesting identities are observed between specific events in the evolution of the flow and the various sub-terms of the
source, and the essence of the sound production mechanism is found to comprise subtle imbalances which disrupt inherent space–time
symmetries which exist between the various sub-terms.
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Keywords: | Aeroacoustics Source-mechanism Shear-flow Vortex-pairing Direct numerical simulation |
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