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This thesis presents a comprehensive study of the qualitative and quantitative aspects of the transient supersonic release from a high-pressure vessel. Experimental contributions are provided to examine the muzzle flows: highly transient, supersonic flows discharged in the vicinity of the firearm muzzle during shooting.About 70% of the chemical energy developed by a conventional ballistic launcher is not converted into kinetic energy of the projectile but is contained in a combustion gas-particle mixture. This highly compressed gas is rapidly discharged from the muzzle in a few milliseconds after the projectile launch. These muzzle flow fields exhibit the structure of an extremely underexpanded supersonic jet encapsulated by an outer blast wave. As it expands, this flow interacts with a precursor one: an identically shaped flow formed by the air initially located upstream of the accelerated projectile and expelled outwards by a piston effect. These phenomena affect (i) the firing signature, (ii) the projectile-flow interaction, and (iii) the launcher accuracy. Hence, an advanced understanding of the muzzle flow is crucial for both launcher designers and users. Even so, the findings in the dynamics of muzzle flows are limited and poorly understood. Only qualitative and intrusive measurementtechniques are performed. This is due to (i) the harsh environment, (ii) the short duration, and (iii) the explosive course during the launch phase.This study aims to improve the probing capability during the intermediate ballistics phase, which takes place in the vicinity of the muzzle between the instants of the in-bore acceleration of the projectile and its free-flight, and gain a better understanding of muzzle flow fields generated by small caliber firearms. Two non-intrusive and whole-field measurement set-ups are performed based on the background oriented schlieren (BOS) and particle image velocimetry (PIV) methods to achieve this goal.First, using the high-speed and time-res, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

This paper presents an original approach to the structural design and analysis of a 3D-printed thermoplastic-core propeller blade for high-altitude UAVs. A macroscale linear isotropic numerical model for the behavior of 3D-printed parts (in Tough PLA, as well as ABS) is fed with values from tensile and bending testing on standard specimens (ISO 527-2/1A and ASTM D5023) before validation by experiments on a representative scaled substitute blade and blade root. The influence of printing parameters, such as material, layer thickness, and raster orientation, is also addressed, as well as variability between prints. To conclude on the validity of the present methodology for complex shapes, a validation of the numerical results with experiments was performed on a scaled 3D-printed twisted blade. The presented macroscale approach to 3D-printed materials was able to predict tensile and bending deformation with good accuracy compared to previously published micro- or meso-scale approaches since it is built from systematic tensile and bending testing on standard specimens to representative blade assemblies. It provides a reliable digital twin for the early design stages of 3D-printed propeller blades. As a proof-of-concept, the validated methodology was then used to design and numerically analyze a large-scale blade using steady one-way Fluid-Structure Interaction in take-off and cruise conditions. The computed stress levels in the blade structure were within safe margins, thereby proving the feasibility of the 3D printing of full-scale propeller blades for high-altitude platforms., SCOPUS: ar.j, info:eu-repo/semantics/published