Dynamique des jets contrôlés : Application à l'étude du mélange dans des écoulements de jets annulaires à très grand rapport de diamètres

Abstract : Turbulent annular jets are flows submitted to strong instabilities which may be a real handicap for many industrial processes (glass fibers processes, personalized ventilation, operational ventilation, burners, snow canons....). These particular axisymetric jets are complex since they are bringing both wake and mixing phenomena. The aim of this study is to determine control methods of the initial zone of air annular jet with great diameter ratio (r=0.91), for high Reynolds numbers (Ree=5130, Ree=2565, Ree=1368, with e the jet ring thickness equal to 2.565mm), in order to meet manufacturer 's needs and to obtain a better understanding of mechanisms used in the flow development. Two methods are studied. A way of passive control by modifying the central obstacle geometry enables to act on the wake and to change the jet shape. Basic, conical and spheroidal annular jets are compared in order to obtain more efficient jets for several industrial processes. An active control, with acoustic forcing, is applied on basic annular jet to reduce annular jet beat around its axis, without changing the nozzle geometry. Different forcing parameters are observed (frequency, forcing position, wave phase) in order to determine an efficient control configuration of flow instabilities. Measurement techniques used are either intrusive (hot wire anemometry) or not (fast tomography, Particle Image Velocimetry, bidimensional and three-dimensional Laser Doppler Anemometry) and are completed by Proper Orthogonal Decomposition (POD) post-processing to analyze coherent structures of the flow and to determine the effect of passive and active control on these structures with different scales. A Direct Numerical Simulation (DNS) is finally suggested in order to model the passive control of turbulent annular jets with great diameter ratios.
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Fluid Dynamics. Université de Rouen, 2009. French


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Contributor : Amélie Danlos <>
Submitted on : Wednesday, December 7, 2011 - 11:41:04 AM
Last modification on : Wednesday, December 7, 2011 - 11:44:39 AM

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Amélie Danlos. Dynamique des jets contrôlés : Application à l'étude du mélange dans des écoulements de jets annulaires à très grand rapport de diamètres. Fluid Dynamics. Université de Rouen, 2009. French. <tel-00649177>

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