Julien Deparday
Experimental fluid dynamics. My research and experience.
I leverage sensors to extract intricate aerodynamic insights through low-order models.
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
I developed a time-resolved instrumented system onboard a 8m long sailing boat. I measured the sail shape, the loads and aerodynamic pressures as well as the wind, and boat motions.
I participated in the development and the experimental campaign to measure the sail shape and aerodynamic pressures produced by a spinnaker on a 10m long sailing boat.
I was responsible for the technical development of the aerodynamic measurement system to be installed on wind turbine blades. The system comprises 40 pressure sensors, 10 microphones and an inertial measurement unit, and had to be thin, minimally intrusive, easy to install, low-power, with wireless transmission.
The wind and water tunnels I used
During my master thesis I used the YRU-Kiel's Twist- Flow Wind Tunnel which is an open-jet wind tunnel, powered by two axial fans for a maximum wind speed of 10 m/s. Rectifiers, screens and twist vanes are used to recreate the height dependent relative flow speed and direction encountered by a sailboat.
During my PhD, I helped my office mates for their experiments in the cavitation tunnel, in which the inflow velocity reaches up to 15 m/s. The pressure in the tunnel test section ranges between 0.1 bar and 3 bar to control the cavitation.
As a guest research assistant during 3 months at the University of Auckland, I used the open jet twisted flow wind tunnel. It has a test section of 7 m wide x 3.5 m high x 5.5 m long, with a maximum wind speed of 8.5 m/s.
During my postdoc at UNFoLD, I participated in the development of the water channel facility and carried out several experimental campaigns. The maximum wind speed is 1m/s. SHARX has a test section of 0.6m x 0.6m x 3m , with acrylic windows on all sides that facilitate the PIV setup.
I participated in the experimental campaign where we placed an airfoil on a cantilever beam. We measured the motions of the beam and the pressure distribution for different excitation frequencies and with different sizes of a crack sawn near the root. The open jet wind tunnel has a test section of 0.45m x 0.45m with a maximum wind speed of 30 m/s.
I coordinated the preparation and running of an experimental campaign in the wind tunnel of ETHZurich. A 3D-printed airfoil was printed and was instrumented with 48 flush pressure measurements. The large subsonic wind tunnel has a test section of 2m x 3m and a maximum wind speed of 60 m/s.
I organised and carried out aeroacoustic measurements in the anechoic wind tunnel of Ecole Centrale Lyon. The maximum wind speed is 150m/s for a test section of 0.3m x 0.4m. For different turbulent inflows, we tested and compared our aeroacoustic measurement system with state-of-the art measurement systems.
We tested our aerodynamic measurement system at high Reynolds on a 1.25m chord long blade in the CSTB's wind tunnel in Nantes. This large wind tunnel is a closed-loop wind tunnel with different sections: aeroacoustic, climatic (temperature from -32°C to +55°C with snow and hail), and aerodynamic. We used the large test section of 5m x 6m, with a maximum wind speed of 45m/s.
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, SwitzerlandSenior 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, SwitzerlandPostdoctoral 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, FranceTeaching 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 ZealandGuest 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 NetherlandsNaval 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, FrancePhD 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, FranceM.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
Python
Arduino/C++
LaTeX
Labview
Catia
Rhinoceros 3D
AutoCAD
3DF Zephyr
Photomodeler
Publications
My publications in peer-reviewed journals are presented here, sorted in different categories.
Timeline
2024
PRFStudy 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
2023
IEEE AccessA 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
2023
AIAA JournalHybrid Model for Inflow Conditions Inference on Airfoils Under Uncertainty
Yuriy Marykovskiy, Julien Deparday, Imad Abdallah, Grégory Duthé, Sarah Barber and Eleni Chatzi
2023
IEEE Instrumentation & Measurement MagazineInstrumentation 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
2022
Wind Energy ScienceDevelopment 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
2022
Journal of Physics: Conference SeriesAerosense: 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
2022
Journal of Physics: Conference SeriesAn experimental system to acquire aeroacoustic properties on wind turbine blades
Julien Deparday, Hanna Müller, Tommaso Polonelli and Sarah Barber
2022
Journal of Fluid MechanicsExperimental quantification of unsteady leading-edge flow separation
Julien Deparday, Xiaowei He, Jeff D. Eldredge, Karen Mulleners and David R. Williams
2021
Journal of Fluids and StructuresThe dynamics and timescales of static stall
Sébastien Le Fouest, Julien Deparday, and Karen Mulleners
2020
AIAA JournalStall Delay and Leading-Edge Suction for a Pitching Airfoil with Trailing-Edge Flap
Guosheng He, Julien Deparday, Lars Siegel, Arne Henning, and Karen Mulleners
2019
Physics of FluidsModeling the interplay between the shear layer and leading edge suction during dynamic stall
Julien Deparday and Karen Mulleners
2018
Ocean EngineeringPerformance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation
Nicolas Aubin, Benoit Augier, Julien Deparday, Mathieu Sacher, and Patrick Bot
2018
Journal of Physics: Conference SeriesCritical evolution of leading edge suction during dynamic stall
Julien Deparday and Karen Mulleners
2018
Journal of Fluids and StructuresExperimental 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
2017
Journal of Sailing TechnologyModal Analysis of Pressures on a Full-Scale Spinnaker
Julien Deparday, Patrick Bot, Frederic Hauville, Benoit Augier, Marc Rabaud, Dario Motta, and David Le Pelley
2016
Ocean EngineeringFull-scale flying shape measurement of offwind yacht sails with photogrammetry
Julien Deparday, Patrick Bot, Fréderic Hauville, Benoit Augier, and Marc Rabaud
2014
Ocean EngineeringExperimental 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