Laetitia PERNOD

Research

1/ Research topics 

My current research focuses on the numerical and experimental characterisation of dynamic fluid-structure interactions between turbulent flows and deformable structures, with or without interactions with the free surface. It aims at, one the one hand, developing flexible lifting surfaces (most often composite) and, on the other hand, providing new physical insights into fluid-structure interaction effects on flexible marine lifting surfaces (e.g. 3D dynamic stall effects at high Reynolds numbers and aspect ratios, characterisation of the forces exerted on the structure and their dimensioning, passive self-adaptation to the flow through bend-twist coupling effects, etc.).  These flexible marine lifting surfaces operate in unsteady viscous turbulent flows and are therefore potentially subject to hydrodynamic excitation sources, such as vortex shedding, laminar-turbulent transition and/or stall. In close collaboration with other researchers at LHEEA and academic and industrial partners, I study the flow regimes and aero-hydroelastic responses of these marine lifting surfaces, as well as their structural deformations under flow-induced vibrations.

The topics of active flow control (e.g. trailing edge morphing using piezoelectric elements, shape memory alloys), passive flow control (e.g. self-adaptation to flow using bend-twist coupling effects), vibration reduction (piezoelectric shunts, viscoelastic materials) and underwater radiated noise reduction, are among the main thematic areas I wish to develop in the short- and medium-terms.

2/ Methods

Whenever possible, I use a joint numerical-experimental method. Concerning the numerical methods, I mainly use high-fidelity RANS CFD fluid simulations (opening up to LES and DNS in progress) coupled with finite element structural dynamic modelling (with ply-by-ply modelling of composites), using strong and weak numerical fluid-structure coupling methods, ALE formulation, etc. The simulations are performed using HPC (High Performance Computing) methods on regional and national supercomputers (e.g. IDRIS - Jean Zay) with industrial and commercial codes (StarCCM+, ISIS-CFD). In addition to the numerical approach, I also contribute to the implementation of experimental methods on these topics, mainly in the test tanks of the LHEEA (hydrodynamic tunnel, twing tank) and IRENav (hydrodynamic tunnel, Naval Academy, Brest): deformation measurements using optical fiber, vibration response measurements using a Doppler laser vibrometer, high-speed camera, etc.

3/ Targeted application areas

The main targeted application areas are naval engineering and the maritime and offshore industries through (i) improving the performance and energy efficiency of marine propulsion (marine propellers, sail propulsion, etc.), (ii) developing innovative appendages (rudders, stabilisers) for seaworthiness, controlling performance in rough seas and decarbonising maritime transport, and (iii) reducing vibrations and noise emitted by lifting surfaces (propellers, appendages, tidal turbine blades, etc.).