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Etude expérimentale de l'interection turbulence cavitation dans un écoulement de marche descendante cavitant : application à la problématique du "blackflow" l'amont des turbopompes de moteurs fusées

Abstract : The present study is inserted in the framework of previous research which aim to get a better understanding of turbulent and cavitating phenomena which occur in the spatial turbopump. Actually, the specific topology of the detached flow which takes place upstream the inducer is today miss-predicted by the standard numerical models.Taking into account the huge complexity of such a flow it has been decided to experimentally investigate the backward-facing step flow which is recognized as a benchmark for numerical simulations and cover a large area of similitude with the backflow upstream the inducers.For this purpose, the mean and turbulent quantities of the liquid phase in the presence of the vapor phase as well as spatio-temporal correlations have been investigated using stereoscopic time resolved PIV, the void ratio has been determined using X-Ray attenuation techniques and measurements have been made for different cavitation levels. The main originality of the present work is based on instantaneous measurements of the wall pressure signals correlated with high speed visualizations, PIV and X-Ray measurements. Specific signal processing as Proper Orthogonal Decomposition and Linear Stochastic Estimation has been performed in order to estimate the velocity-density correlations useful to evaluate the void ratio transport. In this experimental work the physical mechanisms of the vapour phase effects on the large vortex structures, shear layer instability, reattachment wall and reverse flow have been investigated to determine what physical assumptions can be applied in the usual cavitation and turbulence models.It has been found for the cavitating cases that the growth of turbulent kinetic energy is not correlated to mean and turbulent shear stresses. This experimental observation is in contradiction with the Boussinesq hypothesis used for the linear eddy viscosity models.Moreover concerning the phase-change modelization for high void fraction, the barotropic models seem to disagree with our experiments.
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  • HAL Id : tel-01299542, version 1

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Guillaume Maurice. Etude expérimentale de l'interection turbulence cavitation dans un écoulement de marche descendante cavitant : application à la problématique du "blackflow" l'amont des turbopompes de moteurs fusées. Mécanique des fluides [physics.class-ph]. Université de Grenoble, 2014. Français. ⟨NNT : 2014GRENI040⟩. ⟨tel-01299542⟩

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