Job offer

Organisation/Company: Ecole Centrale de Nantes, GeM

Research Field: Engineering Technology » Energy technology, Technology » Materials technology

Researcher Profile: Recognised Researcher (R2), Leading Researcher (R4), First Stage Researcher (R1), Established Researcher (R3)

Country: France

Application Deadline: 30 Apr 2025 - 22:00 (UTC)

Type of Contract: Temporary

Job Status: Full-time

Offer Starting Date: 1 Oct 2025

Is the job funded through the EU Research Framework Programme? Not funded by a EU programme

Is the Job related to staff position within a Research Infrastructure? No

Offer Description

1. Introduction and background

The submarine power cables that transmit the energy produced by offshore wind turbines are exposed to the loadings of underwater installation, external attack and those resulting from hydrodynamic forces and the movement of the turbine platform. Each year, cable-related losses account for an average of 77% of the total cost of losses on offshore wind farms worldwide.

This Ph.D is part of a project funded by the French Environment and Energy Management Agency (ADEME). The aim is to develop a system for modelling, monitoring and predicting the remaining structural lifetime of submarine cables for marine renewable energies. The project partners are Febus Optics, EDF R&D, the Open-C Foundation and Centrale Nantes.

The project is based on a technology for measuring deformation using an optical fibre embedded in the cable. Currently, the specific arrangement of the optical fibres alters the mechanical transfer between the fibres and the various components of the cable. As a result, deformation measurements from the optical fibres alone are insufficient to fully characterize the mechanical state of the cable. This issue has received limited attention to date and is highly dependent on the cable design and its complexity, which varies from one installation to another. This constitutes a significant obstacle to the use of fibre-optic measurements.

2. Description of the Ph.D

In this context, the objective of the Ph.D is to enhance these measurements with numerical simulation results to fully determine the state of the cable.

However, numerical modelling of submarine power cables remains challenging due to their numerous components, some of which have helical geometries, and due to contact non-linearities, which lead to non-linear bending behavior. Additionally, some data (such as the initial stress state, friction coefficients, etc.) are not well known. Furthermore, it is not feasible to use a cable model representing all the details of its structure to analyze a cable several tens of meters long, as this would result in prohibitive computation times.

Therefore, it is necessary to rely on multi-scale approaches that combine detailed local models to accurately represent the cable's components, and simplified global models to determine its overall response.

The main objective of the Ph.D is to use these two models, along with optical fibre measurements, to characterize the complete response of the cable. A methodology to achieve this objective will be established.

The development and validation of this methodology will take place in several stages through tests:

• In the laboratory under controlled conditions on a model cable, through mechanical tests (tensile, bending),
• In a wave basin, at a reduced scale, considering various sea states,
• At sea, at full scale.

The tests in the basin and at sea will be modeled using a code developed by EDF R&D, in which the cable’s non-linear mechanical model will be coupled with a hydro-aero-servo-elastic code that accounts for the entire system (wind turbine, platform, cables, and fluid environment).

Once the overall methodology has been validated, it can also be used to assess the local stresses in the cable components, from which the lifetime of the components can be estimated.

The ultimate goal of the Ph.D is to combine fibre-optic measurements with the results of numerical modelling to better assess cumulative fatigue, ideally updating the cable’s service life consumption.

The main skills required for this Ph.D are:

• Continuum and structural mechanics,
• Numerical and finite element methods.

The person recruited will be present at these tests. However, his/her primary task will be to model the cable at different scales and implement the overall methodology.

Previous work on the local and global modelling of electrical cables has already been performed at GeM at Centrale Nantes and will serve as a starting point for this Ph.D. The work will also be based on software developments carried out at EDF R&D.

Funding category: Contrat doctoral

This project was funded by the French State as part of France 2030 operated by ADEME

PHD title: Mechanics of Solids, Structures, Materials and Interfaces

PHD Country: France

The Ph.D requires skills in continuum and structural mechanics, as well as numerical and finite element methods.