On indirect noise in multicomponent nozzle flows. (12th September 2017)

• Record Type: Journal Article
• Authors: Magri, Luca
• Is Part Of: Journal of fluid mechanics. Volume 828(2017)
• Publication Date: 2017-09-12
• Subjects: acoustics, -- gas dynamics, -- reacting flows; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2017.591
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : A one-dimensional, unsteady nozzle flow is modelled to identify the sources of indirect noise in multicomponent 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.