On indirect noise in multicomponent nozzle flows
Journal of Fluid Mechanics
Cambridge University Press
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Magri, L. (2017). On indirect noise in multicomponent nozzle flows. Journal of Fluid Mechanics, 828 (R2) https://doi.org/10.1017/jfm.2017.591
A one-dimensional, unsteady nozzle flow is modelled to identify the sources of indirect noise in multi-component gases. First, from non-equilibrium thermodynamics relations, it is shown that a compositional inhomogeneity advected in an accelerating flow is a source of sound induced by inhomogeneities in the mixture (i) chemical potentials and (ii) specific heat capacities. Second, it is shown that the acoustic, entropy and compositional linear perturbations evolve independently from each other and they become coupled through mean-flow gradients and/or at the boundaries. Third, the equations are cast in invariant formulation and a mathematical solution is found by asymptotic expansion of path-ordered integrals with an infinite radius of convergence. Finally, the transfer functions are calculated for a supersonic nozzle with finite spatial extent perturbed by a methane-air compositional inhomogeneity. The proposed framework will help identify and quantify the sources of sound in nozzles with relevance, for example, to aeronautical gas turbines.
acoustics, gas dynamics, reacting flows
The author is supported by the Royal Academy of Engineering Research Fellowships Scheme.
Royal Academy of Engineering (RAEng)
External DOI: https://doi.org/10.1017/jfm.2017.591
This record's URL: https://www.repository.cam.ac.uk/handle/1810/270157