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
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
