Julien Deparday
Experimental fluid dynamics. My research and experience.
Archives
Study of the wall pressure variations on the stall inception of a thick cambered profile at high Reynolds number
in Phys. Rev. Fluids, 9, 014605, 2024 We present an experimental study of the aerodynamic forces on a thick and cambered airfoil at a high Reynolds number (Re) (3.6×10^6), which is of direct relevance for wind turbine design. Unlike thin airfoils at low chord-based Reynolds numbers, no consistent description currently exists for the stall process…
Experimental quantification of unsteady leading-edge flow separation
in Journal of Fluid Mechanics, vol. 941, A60, 2022 We propose here a method to experimentally quantify unsteady leading-edge flow separation on aerofoils with finite thickness. The methodology relies on the computation of a leading-edge suction parameter based on measured values of the partial circulation around the leading edge and the stagnation point location. We…
The dynamics and timescales of static stall
in Journal of Fluids and Structures, 104:103304, 2021 Airfoil stall plays a central role in the design of safe and efficient lifting surfaces. We typically distinguish between static and dynamic stall based on the unsteady rate of change of an airfoil’s angle of attack. Despite the somewhat misleading denotation, the force and flow development of…
Stall Delay and Leading-Edge Suction for a Pitching Airfoil with Trailing-Edge Flap
in AIAA Journal, 58(12):5146-5155, 2020 The flow around a pitching NACA0015 airfoil with an oscillating trailing-edge flap is experimentally investigated to characterize the influence of the flap kinematics on the development of dynamic stall. We specifically focus on the timing of the stall development and critical values of the leading-edge suction parameter as potential stall…
Modeling the interplay between the shear layer and leading edge suction during dynamic stall
in Physics of Fluids, 31:107104 , 2019 The dynamic stall development on a pitching airfoil at Re = 106 was investigated by time-resolved surface pressure and velocity field measurements. Two stages were identified in the dynamic stall development based on the shear layer evolution. In the first stage, the flow detaches from the trailing edge…
Critical evolution of leading edge suction during dynamic stall
in Journal of Physics: Conference Series, 1037:022017, 2018 Dynamic stall dominates the aerodynamic performance, the robustness, and the wake dynamics of vertical axis wind turbines. To better assess the dynamic stall onset and its associated unsteady effects, this paper analyzes experimentally the evolution of the leading edge suction vector on a sinusoidally pitching airfoil based…
Experimental analysis of a strong fluid-structure interaction on a soft membrane – Application to the flapping of a yacht downwind sail
in Journal of Fluids and Structures, 81:547–564, 2018 In the present study we investigate the flapping instability of a light, soft, highly cambered membrane subject to wind loading. An original in-situ experiment is developed where time-resolved pressures and forces are measured on a full-scale yacht downwind sail called a spinnaker. Particular features of this aero-elastic…
Modal Analysis of Pressures on a Full-Scale Spinnaker
in Journal of Sailing Technology, 05:1–21, 2017 While sailing offwind, the trimmer typically adjusts the downwind sail “on the verge of luffing”, occasionally letting the luff of the sail flap. Due to the unsteadiness of the spinnaker itself, maintaining the luff on the verge of luffing requires continual adjustments. The propulsive force generated by the…