Confinement de la détonation d'un objet explosif par mousse aqueuse sèche. Etude expérimentale et numérique

Abstract : In order to improve the protection of goods and persons, the French CEA DAM is interested in aqueous foams for their ability to mitigate the detonation outcome. Two objectives are put forward. The first one is to attenuate the blast effects induced by the detonation of an explosive device. The second one is to slow down or to capture potentially harmful solid particles, which could be dispersed by the considered device.As such, the aim is to understand the underlying physics of such phenomenon. Several experiments have been undertaken and compared to a multiphase numerical modelling.Aqueous foam is a two-phase medium, composed of gaseous bubbles within a liquid matrix made of films and Plateau Borders. This study focuses on dry aqueous foams, i.e. with a liquid volumic fraction lower than 5%. The presentation of the study is divided into three parts. The first one deals with the shock wave propagation through aqueous foam. An experimental campaign on a shock tube, at ENSTA Bretagne, is presented, whose results highlight the influence of the gas which fills the cells of the foam on the shock front behavior.The second part is related to the blast wave attenuation. Two experimental campaigns were conducted: one in a detonation tube with a reactive gaseous mixture, at ISAE-ENSMA and another one, using condensed explosive, at CEA/Gramat. In both cases, the results lead to the mitigation of the detonation induced blast effects.There is a good agreement between these three experimental results and the numerical results from the multiphase model. This enables us to clarify the phenomenology and quantify the different interphase exchange, which evolve as the foam fragmentation proceeds in two steps.The last part is about the aqueous foam ability to slow down or to capture micrometric particles. Two campaigns were conducted on this subject. The first one studied the high velocity dynamics of a cloud of particles propelled by an explosive into an aqueous foam. Using X-ray radiography, both the position and the shape of the cloud are analysed during its propagation through the foam. A strong decrease in speed of the particles is observed. The second campaign aimed to quantify the particle ratio captured by an aqueous foam confinement. To that end, several sizes of aqueous foam confinement have been compared. The results show the good properties of the foam to inhibit the particle dispersal by an explosive.
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Félix Ballanger. Confinement de la détonation d'un objet explosif par mousse aqueuse sèche. Etude expérimentale et numérique. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2016. Français. ⟨NNT : 2016ESMA0011⟩. ⟨tel-01404678⟩

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