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Postdoc on Modelling of turbulent jet and airfoil noise at LadHyX/IMSIA, Paris (France)

Du 1 octobre 2021 au 31 janvier 2022

Starting date : now
Duration : 2 years.
Site actualite
Ladhyx and IMSIA Labs
ENSTA & Ecole Polytechnique
Contact:
Lutz Lesshafft lutz.lesshafft@ladhyx.polytechnique.fr
Benjamin Cotté benjamin.cotte@ensta-paris.fr

The objective of the present project is to develop numerical tools to identify near-field fluctuations that optimally radiate sound, both in subsonic jets and in the flow around an airfoil. The study programme is based on theoretical concepts from linear instability analysis and from aeroacoustics.

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Two-year Postdoc position at Institut Polytechnique de Paris: Modelling of turbulent jet and airfoil noise

Turbulence in shear flows, such as jets, wakes and boundary layers, is known to contain energetic structures of high spatial and temporal coherence, which are the dominant sources of aeroacoustic sound. In recent years, it has been demonstrated that these coherent structures can be modelled as linear fluctuations around the turbulent mean flow: such modelling is theoretically well-founded, and leads to quantitatively correct resultsa.

A turbulent jet: near-field temperature and far-field pressure fluctuationsb

Similar modelling of the associated aeroacoustic sound field remains an open field of study at present. An important prerequisite for such studies is an efficient numerical tool, which would allow to resolve the short length scales of the turbulent near field as well as the long acoustic wavelengths over a sufficiently large portion of the far field.

The objective of the present project is to develop such a numerical tool, by use of unstructured meshes and the finite-element package FEniCS. This code will then be used to identify near-field fluctuations that optimally radiate sound, both in subsonic jets and in the flow around an airfoil. The study programme is based on theoretical concepts from linear instability analysis and from aeroacoustics.

The position is based at the Laboratoire d’Hydrodynamique (LadHyX, Ecole Polytechnique) dur- ing the first year, and at the Institute of Mechanical Sciences and Industrial Applications (IMSIA, ENSTA Paris) during the second year. Funding for two years of full-time employment is provided by the Agence de l’Innovation de Défense. Candidates must hold a PhD degree in a field related to fluid mechanics.

Contact:
Lutz Lesshafft lutz.lesshafft@ladhyx.polytechnique.fr
Benjamin Cotté benjamin.cotte@ensta-paris.fr

aLesshafft, Semeraro, Jaunet, Cavalieri & Jordan (2019): Resolvent-based modelling of coherent wavepackets in a turbulent jet. Physical Review Fluids, vol. 4, art. 063901.

bBrès et al. (2018): Importance of the nozzle-exit boundary-layer state in subsonic turbulent jets. Journal of Fluid Mechanics, vol. 851, p. 83-124.