Hiring Institution
École Centrale de Lyon (EC Lyon)

PhD-Awarding Institutions
École Centrale de Lyon (EC Lyon)
The University of Adelaide (UoA)

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Option 1

Wall pressure spectra modelling beneath a boundary layer submitted to pressure gradient

The study of wall pressure fluctuations beneath a turbulent boundary layer has drawn the attention of researchers for decades due to their importance in a wide range of applications dealing with vibro-acoustics or aero-acoustics. Applications can be found in the automotive and aeronautical industries, as well as in hydroacoustic studies focused on marine technology, to cite only a few. Intensive research has been carried into the field over the past seventy years or so, at first mostly in the absence of pressure gradient. Contrary to what can be obtained for the turbulent velocity spectra, we observe a significant disparity in the measurements. These measurements are indeed difficult to perform, with sensors that do not allow to resolve the spectra to viscous scales. Moreover, pressure is a non-local quantity that probably integrates various installation effects. There are still open questions and ongoing research linked to the experimental or numerical characterisation of wavenumber – frequency spectra, and the ability to account for pressure gradient effects. We propose to make progress in the modelling, in the context of naval applications with a convection Mach number quite distinct from that of acoustics, and by focusing on the convective spot in the wavenumber – frequency space. A review of the measurements available for both the pressure spectra and the spectral velocity tensor inside the boundary layer, key data that appear in the analytical developments, will be performed, as well as a critical state of the art of fluctuating parietal pressure spectra models. A rational modelling will be developed by validating each intermediate step with numerical or experimental data, and numerical simulations will complete missing data required for assessing the analytical developments. Turbulent flow simulations where a constant pressure gradient can be applied to the established turbulent boundary layer will be privileged.

Option 2

Numerical modelling wall pressure fluctuation spectrum beneath a boundary layer submitted to pressure gradient

The study of wall pressure fluctuations beneath a turbulent boundary layer has drawn the attention of researchers for decades due to their importance in a wide range of applications dealing with vibro-acoustics or aero-acoustics. Applications can be found in the automotive and aeronautical industries, as well as in hydroacoustic studies focused on marine technology, to cite only a few. Intensive research has been carried into the field over the past seventy years or so, at first mostly in the absence of pressure gradient. Contrary to what can be obtained for the turbulent velocity spectra, we observe a significant disparity in the measurements. These measurements are indeed difficult to perform, with sensors that do not allow to resolve the spectra to viscous scales. Moreover, pressure is a non-local quantity that probably integrates various installation effects. There are still open questions and ongoing research linked to the experimental or numerical characterisation of wavenumber – frequency spectra, and the ability to account for pressure gradient effects. A special emphasis will be placed on controlling the pressure gradient applied to turbulent boundary layers in equilibrium in pipes or channel flows to obtain reliable numerical data. We then propose to make progress in the modelling of the convective spot in the wavenumber – frequency space, and to obtain wall pressure spectra as a result of their integration in Fourier space.

Option 3

Wall pressure spectra beneath a boundary layer in equilibrium submitted to pressure gradient

The study of wall pressure fluctuations beneath a turbulent boundary layer has drawn the attention of researchers for decades due to their importance in a wide range of applications dealing with vibro-acoustics or aero-acoustics. Applications can be found in the automotive and aeronautical industries, as well as in hydroacoustic studies focused on marine technology, to cite only a few. Intensive research has been carried into the field over the past seventy years or so, at first mostly in the absence of pressure gradient. Contrary to what can be obtained for the turbulent velocity spectra, we observe a significant disparity in the measurements. These measurements are indeed difficult to perform, with sensors that do not allow to resolve the spectra to viscous scales. Moreover, pressure is a non-local quantity that probably integrates various installation effects. There are still open questions and ongoing research linked to the experimental or numerical characterisation of wavenumber – frequency spectra, and the ability to account for pressure gradient effects. We propose to make progress in the modelling, in the context of naval applications with a convection Mach number quite distinct from that of acoustics, and by focusing on the convective spot in the wavenumber – frequency space. To be able to study the influence of various pressure gradients, but in a controlled environment, we will be interested in numerical simulations in channels with variable cross-section. The selection of a suitable design could guide an experimental part where pressure spectra in the wavenumber-frequency space are measured using MEMS antenna.

Christophe Bailly
Christophe Bogey
Rey Chin

Turbulence modelling, Computational Fluid Dynamics, signal processing, wall-bounded flows