Julien Deparday

Specialised in experimental fluid dynamics, with a strong emphasis on field measurements and unsteady aerodynamics, my research interests incude fluid-structure interaction, flow separation, and inviscid flow theory for naval engineering, wind energy and aeronautics applications. I believe that interdisciplinary collaboration, diversity, and inclusion are essential for successful experimental projects.

What I Do

Experiments

I carry out experiments using wind tunnels, water channels, and in the field. I use particle image velocimetry, pressure sensors, loads cells, inertial measurement unit, photogrammetry...

Low-order models

I extract and estimate the most important aerodynamic features to understand the physics of what is happening. I often use the inviscid flow theory and data-driven methods such as the POD.

Unsteady flow

I study the influence of unsteady flows on engineering systems including wind turbines, drones, helicopters and ships. I work with turbulent and gusty inflow and moving structures.

Flexible membrane

I study the strong fluid-structure interaction of a membrane that takes its shape according to the wind loading and affects in return the flow around it. My main application is on sails.

My main field measurement campaigns

The wind and water tunnels I used

The courses I have taught

I gave lectures and practical work on engineering drawing and mechanism study at a master level at Ecole Navale for 25 hours per year during 4 years.

The goal of this course was to teach the basics of engineering drawing (visible and hidden outlines, multi-view projections, …) as well as the vocabulary and theuse of the main mechanical parts. With a set of technical drawings more and more complex, (with real technical drawings present onboard the Navy vessels), the students must “extract” and draw different parts from the drawings.
As a teacher, I helped them individually to understand the drawings. When a new standard mechanical part was found, I described it to the whole class and explained its purpose.

As part of the practical works in the measurement technique course for the master degree at Ecole Navale, I taught during 2 years (24 hours per year) how to calibrate a force sensor. A load cell had to be calibrated to assess the different errors (hysteresis, precision and linearity errors). The aim of this practical work was also an active exercise of Excel or Matlab with input of complex formulas and handling large database.

I taught different courses in the field of naval engineering:

Ship structure during 2 years. The ship structure course provided students with the basics of structural design and calculations (Young Modulus, bending and shear stress, beam diagrams…) and the application on ships. My previous experience as a naval engineer in ship structure allowed me to contribute ideas and opinions as the course evolved.
During two years, I gave a practical work on Excel. I also proposed new topics where ship stability and ship structure were linked.

Sailing yacht during 3 years. The lecture on sailing yacht engineering was an application of all the previous courses that the Master students learned during the semester. I created and presented a 5-hour lecture and a practical work. The idea was to demonstrate how the previous courses they had (stability, lifting profiles, bluff bodies, seakeeping,…) could be applied to sailing yachts. The practical work was to create a simple Velocity Prediction Program to estimate the performance of a one design class J/80 sailing yacht. The course was very much appreciated. It helped them to understand some physical concepts they did not fully understand in the previous courses.

During the course of aerodynamics for the Master at EPFL, I gave a 2-hour lecture during 2 years on the basics of potential flow to the students. I introduced the concept of potential and stream functions, as well as the superposition principle using sources and sinks.

During 2 years at EPFL, I actively participated at the presentation of our work to children from the age of 8 to 16. The idea was to demonstrate how fluid mechanics is everywhere and how we can visualise them in a fun way. For example by letting them play with vortex cannons!

I gave practical work during 4 years (24 hours) and tutorials during 2 years (20 hours) at Ecole Navale. The ship stability course provides cadets (master students) with the main principles of ship intact stability (buoyancy,
righting moment, metacentric height…), the free surface effect and stability curves and tables.

In conjunction with the lecturing professor, I was responsible for the tutorials and the practical work.During the practical work on stability, the students used an instrumented simple shape hull in a basin to study the influence of the position of the gravity centre and to compare the experimental results with their calculations. I reorganised the practical work and rewrote the guidelines  to be more job-oriented.

 

For more than 10 years, I have had the opportunity to supervise many projects at the bachelor and master levels. I proposed various subjects in mechanics, fluid dynamics, electronics, code development… At EPFL, I proposed and supervised an original multi-year long project on the physics of a single-oar sculling, known as godille in Brittany.

I designed and gave a 2-hour introductory lectures during 2 years on unsteady aerodynamics at EPFL as part of the Aerodynamics course given by Pr. Mulleners.

A few photos of my work

Resume

Education

Since 2020
OST-Eastern Switzerland University of Applied Sciences, Rapperswil, Switzerland

Senior scientist

Researcher at the Wind Energy group, in the Institute for Energy Technology:

  • Mistery project (2023-2026), funded by SNSF in Switzerland and ANR in France for
    2mCHF:
    • modelling and estimation of unsteady aerodynamic flow at high Reynolds number,
    • coordinator of the project with 4 partners: OST, ETHZ, CentraleSup´elec, and Ecole
      Centrale Nantes,
    • aerodynamic experiments in a large-scale wind tunnel at CSTB in Nantes, France
      on a blade section with a chord of 1.25m.
  • Aerosense project (2020-2023), , funded by SNSF and Innosuisse as a Bridge - Discovery
    programme for 1.6 mCHF:
    • developed an aerodynamic measurement system to be installed on wind turbine blades which is thin, minimally intrusive, easy to install, low-power, with wireless transmission, comprising 40 pressure sensors, 10 microphones and an inertial measurement unit,
    • responsible for the technical development of the aerodynamic measurement system: close communication with electronic researchers, mechanical engineers and computer researchers,
    • developed the corrections and calibration methods to acquire accurate measurements.
  • Project leader of a research and development collaboration with a Swiss company, Netico, funded by the Swiss Innovation Agency on machine learning and in-field measurements.
  • Supervised bachelor and master projects.
2017-2020
EPFL - Ecole Polytechnique Fédérale de Lausanne, Switzerland

Postdoctoral research associate

Post-doc at UNFoLD, in the Mechanical Engineering Institute:

Experimental study of the aerodynamic performance of vertical axis wind turbine in the SMART-H project funded by the Swiss National Science Foundation.

  • developed low-order models of aerodynamic performance,
  • prepared, carried-out and post processed experiments.

Proposed and supervised master and bachelor projects. Contributed to courses and tutorials in fluid mechanics and aerodynamics courses.

Safety coordinator of the lab.

2012-2016
Ecole Navale, IRENav, Brest, France

Teaching and research assistant

PhD student and teaching assistant in the Mechanical and Energetical Engineering in Naval Environment department (M2EN):

Experimental study of fluid-structure interaction on downwind sails:

  • developed time-resolved instrumented system onboard a sailing boat measuring sail shape, wind, loads, aerodynamic pressures and boat motions,
  • co-developed and used custom-made pressure sensors with the University of Auckland,
  • developed calibration and measurement algorithms for custom-made load cells and inertial measurement units,
  • designed a unique photogrammetric system to measure flying shape of downwind sails,
  • planned and conducted full-scale in-situ testing, led a team of 6 persons,

Taught 100h per year of lectures, tutorials and practical work to naval officer trainees (master level) and to master students.

2014
University of Auckland, New Zealand

Guest Research Assistant

3 month secondment at the Yacht Research Unit in the Mechanical Engineering department, to conduct wind tunnel and full-scale experiments in a UK-France-NZ collaboration project SailingFluids funded by the European Union's FP7-people and by the Royal Society of New Zealand.

2010-2012
C-Job & Partners BV, Hoofddorp, the Netherlands

Naval Engineer

  • designed structure and general arrangement for various types of vessels such as dredgers, heavy lift vessels, offshore installation vessels, mega yachts,
  • wrote reports and technical drawings in compliance with guidelines and classification societies,
  • analysed seakeeping for feasibility studies of offshore operations.

Education

2016
Université Bretagne Occidentale - Ecole Navale, Brest, France

PhD in Mechanical Engineering

doctoral thesis: Experimental studies of Fluid-Structure Interaction on Downwind sails
supervisors:

  • Prof M. Rabaud - FAST Université Paris Sud,
  • Dr. P. Bot - IRENav Ecole Navale,
  • Dr. F. Hauville - IRENav Ecole Navale

grade: Highest distinction: Mention très honorable à l'unanimité du jury.

2010
ENSTA Bretagne, Brest, France

M.Sc. in Mechanical Engineering

Diplôme d'Ingénieur

Studied in Naval and Offshore architecture, specialized in hydrodynamics.


master thesis: Spinnaker Flying Shape determination: Comparison of a spinnaker model in a Twisted Flow Wind Tunnel with a full scale spinnaker using photogrammetric measurements.
supervisors: Prof. Dr.-Ing K. Graf, Dr. K. Roncin

Knowledges

  • Aerodynamics
  • Potential flow
  • Fluid-structure interaction
  • Beam structure
  • Engineering drawing
  • Naval engineering
  • Ship stability
  • Seakeeping

Measurement knowledges

  • High speed particle image velocimetry
  • Pressure sensor
  • Load cell and strain gauge
  • Inertial measurement unit
  • Photogrammetry

Skills

Matlab

85%

Python

60%

Arduino/C++

40%

LaTeX

90%

Labview

30%

Catia

70%

Rhinoceros 3D

85%

AutoCAD

60%

3DF Zephyr

75%

Photomodeler

75%

Publications

My publications in peer-reviewed journals are presented here, sorted in different categories.

Study of the wall pressure variations on the stall inception of a thick cambered profile at high Reynolds number

Study of the wall pressure variations on the stall inception of a thick cambered profile at high Reynolds number

Mistery, Unsteady flow, Wind tunnel
A Self-Sustainable and Micro-Second Time Synchronised Multi-Node Wireless System for Aerodynamic Monitoring on Wind Turbines

A Self-Sustainable and Micro-Second Time Synchronised Multi-Node Wireless System for Aerodynamic Monitoring on Wind Turbines

Aerosense, Field measurements
Hybrid Model for Inflow Conditions Inference on Airfoils Under Uncertainty

Hybrid Model for Inflow Conditions Inference on Airfoils Under Uncertainty

Aerosense, Potential flow, Wind tunnel
Instrumentation and Measurement Systems: Aerosense: A Wireless, Non-Intrusive, Flexible, and MEMS-Based Aerodynamic and Acoustic Measurement System for Operating Wind Turbines

Instrumentation and Measurement Systems: Aerosense: A Wireless, Non-Intrusive, Flexible, and MEMS-Based Aerodynamic and Acoustic Measurement System for Operating Wind Turbines

Aerosense, Field measurements
Development of a wireless, non-intrusive, MEMS-based pressure and acoustic measurement system for large-scale operating wind turbine blades

Development of a wireless, non-intrusive, MEMS-based pressure and acoustic measurement system for large-scale operating wind turbine blades

Aerosense, Field measurements
Aerosense: Long-Range Bluetooth Wireless Sensor Node for Aerodynamic Monitoring on Wind Turbine Blades

Aerosense: Long-Range Bluetooth Wireless Sensor Node for Aerodynamic Monitoring on Wind Turbine Blades

Aerosense, Field measurements, Wind tunnel
An experimental system to acquire aeroacoustic properties on wind turbine blades

An experimental system to acquire aeroacoustic properties on wind turbine blades

Aerosense, Wind tunnel
Experimental quantification of unsteady leading-edge flow separation

Experimental quantification of unsteady leading-edge flow separation

Potential flow, Smart-H, Unsteady flow, Wind tunnel
The dynamics and timescales of static stall

The dynamics and timescales of static stall

Smart-H, Unsteady flow, Wind tunnel
Stall Delay and Leading-Edge Suction for a Pitching Airfoil with Trailing-Edge Flap

Stall Delay and Leading-Edge Suction for a Pitching Airfoil with Trailing-Edge Flap

Potential flow, Smart-H, Unsteady flow, Wind tunnel
Modeling the interplay between the shear layer and leading edge suction during dynamic stall

Modeling the interplay between the shear layer and leading edge suction during dynamic stall

Potential flow, Smart-H, Unsteady flow, Wind tunnel
Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

Flexible membrane, SailingFluids, Wind tunnel
Critical evolution of leading edge suction during dynamic stall

Critical evolution of leading edge suction during dynamic stall

Potential flow, Smart-H, Unsteady flow, Wind tunnel
Experimental analysis of a strong fluid-structure interaction on a soft membrane – Application to the flapping of a yacht downwind sail

Experimental analysis of a strong fluid-structure interaction on a soft membrane – Application to the flapping of a yacht downwind sail

Field measurements, Flexible membrane, SailingFluids, Unsteady flow
Modal Analysis of Pressures on a Full-Scale Spinnaker

Modal Analysis of Pressures on a Full-Scale Spinnaker

Field measurements, SailingFluids, Unsteady flow
Full-scale flying shape measurement of offwind yacht sails with photogrammetry

Full-scale flying shape measurement of offwind yacht sails with photogrammetry

Field measurements, Flexible membrane, SailingFluids
Experimental investigation of asymmetric spinnaker aerodynamics using pressure and sail shape measurements

Experimental investigation of asymmetric spinnaker aerodynamics using pressure and sail shape measurements

Field measurements, Flexible membrane, SailingFluids

Timeline

2024
PRF

Study of the wall pressure variations on the stall inception of a thick cambered profile at high Reynolds number

Caroline Braud, Bérengère Podvin and Julien Deparday

more info

2023
IEEE Access

A Self-Sustainable and Micro-Second Time Synchronised Multi-Node Wireless System for Aerodynamic Monitoring on Wind Turbines

Tommaso Polonelli, Amirhossein Moallemi, Weikang Kong, Hanna Müller, Julien Deparday, Michele Magno and Luca Benini

more info

2023
AIAA Journal

Hybrid Model for Inflow Conditions Inference on Airfoils Under Uncertainty

Yuriy Marykovskiy, Julien Deparday, Imad Abdallah, Grégory Duthé, Sarah Barber and Eleni Chatzi

more info

2023
IEEE Instrumentation & Measurement Magazine

Instrumentation and Measurement Systems: Aerosense: A Wireless, Non-Intrusive, Flexible, and MEMS-Based Aerodynamic and Acoustic Measurement System for Operating Wind Turbines

Tommaso Polonelli, Julien Deparday, Imad Abdallah, Sarah Barber, Eleni Chatzi, Michele Magno

more info

2022
Wind Energy Science

Development of a wireless, non-intrusive, MEMS-based pressure and acoustic measurement system for large-scale operating wind turbine blades

Sarah Barber, Julien Deparday, Yuriy Marykovskiy, Eleni Chatzi, Imad Abdallah, Grégory Duthé, Michele Magno, Tommaso Polonelli, Raphael Fischer, and Hanna Müller

more info

2022
Journal of Physics: Conference Series

Aerosense: Long-Range Bluetooth Wireless Sensor Node for Aerodynamic Monitoring on Wind Turbine Blades

Tommaso Polonelli, Julien Deparday, Hanna Müller, Raphael Fischer, Luca Benini, Sarah Barber and Michele Magno

more info

2022
Journal of Physics: Conference Series

An experimental system to acquire aeroacoustic properties on wind turbine blades

 Julien Deparday, Hanna Müller, Tommaso Polonelli and Sarah Barber

more info

2022
Journal of Fluid Mechanics

Experimental quantification of unsteady leading-edge flow separation

Julien Deparday, Xiaowei He, Jeff D. Eldredge, Karen Mulleners and David R. Williams

more info

2021
Journal of Fluids and Structures

The dynamics and timescales of static stall

Sébastien Le Fouest, Julien Deparday, and Karen Mulleners

more info

2020
AIAA Journal

Stall Delay and Leading-Edge Suction for a Pitching Airfoil with Trailing-Edge Flap

Guosheng He, Julien Deparday, Lars Siegel, Arne Henning, and Karen Mulleners

more info

2019
Physics of Fluids

Modeling the interplay between the shear layer and leading edge suction during dynamic stall

Julien Deparday and Karen Mulleners

more info

2018
Ocean Engineering

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

Nicolas Aubin, Benoit Augier, Julien Deparday, Mathieu Sacher, and Patrick Bot

more info

2018
Journal of Physics: Conference Series

Critical evolution of leading edge suction during dynamic stall

Julien Deparday and Karen Mulleners

more info

2018
Journal of Fluids and Structures

Experimental analysis of a strong fluid-structure interaction on a soft membrane - Application to the flapping of a yacht downwind sail

Julien Deparday, Benoit Augier, and Patrick Bot

more info

2017
Journal of Sailing Technology

Modal Analysis of Pressures on a Full-Scale Spinnaker

Julien Deparday, Patrick Bot, Frederic Hauville, Benoit Augier, Marc Rabaud, Dario Motta, and David Le Pelley

more info

2016
Ocean Engineering

Full-scale flying shape measurement of offwind yacht sails with photogrammetry

Julien Deparday, Patrick Bot, Fréderic Hauville, Benoit Augier, and Marc Rabaud

more info

2014
Ocean Engineering

Experimental investigation of asymmetric spinnaker aerodynamics using pressure and sail shape measurements

Dario Motta, Richard G.J. Flay, Peter J. Richards, David J. Le Pelley, D., Julien Deparday, and Patrick Bot

more info

Contact

Rapperswil-Jona, Switzerland

aero@juliendeparday.com

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