PhD offer - Wind turbine wake in a turbulent background

Description of the PhD offer

Development of carbon-free energy production is a major societal and environmental issue. Among the most attractive solutions, wind energy occupies a particularly important place as emphasized in the IPCC proposals to combat global warming. Although this sector has entered a more mature phase, there are still many issues that arise regarding the reliability of wind farm performance predictions. These issues are closely linked to the way in which wind turbine wakes develop and interact with their environment.
Consequently, the modelling of these flows is crucial to predict, or even improve, the efficiency of wind energy production. In field conditions, wind turbine wakes are subject to external disturbances because the ambient flow is itself turbulent. While several studies have shown that background turbulence affects wake development, few reliable models have been proposed so far to take into account the influence of external turbulence.
This shows that the modelling of wind turbine wakes in realistic conditions is still fragile and that fundamental studies of these flows are necessary to fill this lack of understanding.

This doctoral thesis aims to tackle this issue by studying in depth the physical mechanisms governing the expansion of a wind turbine wake within a turbulent background.
To this end, the work will be based on the combination of high-quality experiments and high-fidelity simulations.
Particular attention will be paid to the influence of the characteristic quantities of the external turbulence on the aerodynamic performance of the wind turbine, on the expansion of its wake and its dynamics.
The physical analysis of experimental and numerical data will ultimately make it possible to propose new models of wake expansion that are more relevant than those currently used for the design of wind farms.

To understand the physics of the wind wake in a turbulent environment, the work will be based on two complementary approaches:

• The experimental work will be carried out within the PRISME laboratory of the University of Orléans, which has been working for several years on the study of wind turbine wakes.
  In the continuity of recent work carried out within the host team, wind tunnel tests will be carried out.
  In particular, optical methods coupled with point measurements will be implemented to study the impact of background turbulence on the development of the wake of a scale-down wind turbine.
• The numerical simulations will be carried out within the CORIA laboratory of the University and INSA Rouen Normandie and CNRS. They will be performed using the massively parallel platform YALES2 dedicated to high-fidelity Large-Edy Simulations (LES).
  In this part, we will focus on understanding the mechanisms of local interactions between the wind turbine wake and its environment.
  The experimental data will be used to parameterize the numerical simulations.
  The latter will be used to formulate a new model of wake expansion whose performance will be assessed against the experimental results.

The new insights that will be raised during this PhD will enable to predict more precisely the interaction of the wind turbine with its environment.
Ultimately, this detailed understanding will be valuable for optimizing both wind energy production and also for designing control devices to improve performance and reduce operating costs.

Working environment

This PhD will benefit from an extremely favourable working environment in terms of resources and know-how.
The candidate who will be recruited will integrate the Flows and Aerodynamic Systems (ESA) group of the PRISME laboratory at the University of Orléans. The research activities of this group relate to the understanding, modelling and control of wake flows representative of industrial applications. In particular, the work will be based on know-how developed over several years on the study of wind turbine wakes. The PRISME laboratory has large test facilities including wind tunnels which will be used during the project. A specific work on the generation of the background turbulence and on the identification of the wake’s boundaries will be carried out initially. Once validated, the experimental setup will be used to carry out a parametric test campaign. The generated database will then be post-processed and analysed.

Although the thesis will mainly take place in the PRISME laboratory, short stays in the CORIA laboratory of the University of Rouen, which has been working for several years on issues directly related to the PhD subject, will be organized regularly. The objective here is to practice on the numerical tools for high-fidelity simulation and to conduct an investigation of the physical mechanisms governing the expansion of the wake in a turbulent environment. Here too, most of the tools to be used are already operational.

The PhD student will be accompanied by researchers from both laboratories for the handling and use of these tools.

In addition, the PhD student will benefit from exchanges with internationally renowned researchers as well as major industrials in the wind energy sector through collaborations initiated by the 2 laboratories involved.

Expected skills

We are looking for a highly motivated PhD student (F/M), holding a Master degree in physics or mechanical engineering with strong background in fluid mechanics and turbulence.
The successful applicant should have a pronounced interest in both experiments and simulations.
The PhD student will be deeply involved in dissemination of the results in project reports, peer-reviewed journals, and presentations in international conferences.
Therefore, high communication and writing skills in English are mandatory.

How to apply

Send your CV, motivation letter, transcript of marks (even partial) of Master and the contact details of two scientific referees before April, 26th, 2023 to nicolas.mazellier@univ-orleans.fr, cedric.raibaudo@univ-orleans.fr and pierre.benard@coria.fr.