{"id":11617,"date":"2020-10-17T01:02:34","date_gmt":"2020-10-17T01:02:34","guid":{"rendered":"http:\/\/isb24news.com\/images\/?p=11617"},"modified":"2020-10-05T21:27:53","modified_gmt":"2020-10-05T21:27:53","slug":"rencontre-du-non-lineaire","status":"publish","type":"post","link":"https:\/\/isb24news.com\/images\/2020\/10\/17\/rencontre-du-non-lineaire\/","title":{"rendered":"Rencontre Du Non Lin\u00e9aire"},"content":{"rendered":"

90 Laminar-turbulent pattern in plane Couette flow 83 quantitatively it leads to a downward shift of R g, R t, and it is not obvious that it is still effective in describing properties of the long term dynamics of bands, in particular pattern stability and band breaking, at a sufficiently accurate level. As a matter of fact it was shown in Fig. 1 that, within these restrictions, stable bands three, two, and even one could be observed with N y 15 in a periodic domain over time spans much larger than 10 4 time units hu. Recent results for PCF in a quasi-one-dimensional geometry 8 show that the decay of turbulence at R g is well accounted for by a continuous second order non-equilibrium phase transition in the directed percolation DP class. Knowing that spatiotemporal correlations are strongly dependent on confinement characteristics 9, it seems important to scrutinize the quasi-two-dimensional case of interest in experiments. It seems clear that under-resolved simulations need not be continued and that the indications obtained in this context have to be confirmed by fully resolved computations. The dynamics of multi-band states and the stability of one-band states while varying the domain size and its geometrical proportions since, owing to periodic boundary conditions, this controls the angle of bands should then be studied with two ideas in mind: i while decreasing R from R t, explore the putative extremum of the potential from which an envelope equation would derive, yielding a preferred wavelength and angle at given R, if any; ii examine whether the transition at R g is continuous as implied in the DP scenario, or else discontinuous with finite turbulent fraction at R g. On the one hand, criticality at R g in the continuous case is likely more difficult to ascertain in the quasi-2d case ideally requiring a finite-size scaling approach than in the quasi-1d case for which convincing results have been obtained 8. On the other hand, a discontinuous transition at R g is forcedly less sensitive to size effects due to the primary role played by extreme localized excursions toward laminar flow 7, with a variety of band configurations possible above R g, hence a finite range of turbulent fraction depending on the geometry, and no turbulence at all in the long term below R g. The main merit of our preliminary study at reduced resolution is therefore to help us better situating the problem not of the nature of turbulence but of the nature of the transition and how to describe it at the global level. Acknowledgements: The author would like to thank the members of the JSPS-CNRS collaboration TransTurb for discussions related to the work presented here, in particular G. Kawahara and M. Shimizu Osaka, T. Tsukahara Tokyo on the Japanese side, and Y. Duguet LIMSI, R. Monchaux and M. Couliou ENSTA-ParisTech on the French side. References 1 A. Prigent, G. Gr\u00e9goire, H. Chat\u00e9 O. Dauchot, Long wavelength modulation of turbulent shear flows, Physica D, 174, 2003 2. L S. Tuckerman, D. Barkley O. Dauchot, Instability of uniform turbulent plane Couette flow: Spectra, probability distribution functions and K \u03a9 closure model, 7th IUTAM Symposium on Laminar-Turbulent Transition, Stockholm, Ph. Schlatter, D. Henningson, eds, pp, Springer 2009 3. P. Manneville, Turbulent patterns in wall-bounded flows: a Turing instability? Europhys Lett, 98, 2012 4. D. Barkley L S. Tuckerman Mean flow of turbulent-laminar patterns in plane Couette flow, J. Fluid Mech, 576, 2007 5. P. Manneville, Dissipative structures and weak turbulence, Academic Press 1990 6. P. Manneville J. Rolland, On modelling transitional turbulent flows using under-resolved direct numerical simulations: The case of plane Couette flow, Theor Comput. Fluid Dyn, 25, 2011 7. P. Manneville, On the decay of turbulence in plane Couette flow, Fluid Dyn Res, 43, 2011 8. G. Lemoult, L. Shi, K. Avila, S V. Jalikop, M. Avila B. Hof, Directed percolation phase transition to sustained turbulence in Couette flow. To be published in Nature Phys 2016. 9 J. Philip P. Manneville, From temporal to spatiotemporal dynamics in transitional plane Couette flow, Phys Rev. E, 83, 2011. Conf\u00e9rence en lhonneur de Claude Lobry, Universit\u00e9 Gaston Berger, Saint Louis S\u00e9n\u00e9gal- An Internet-based graphical programming tool for teaching power system harmonic measurement Oops! Something went wrong while submitting the form. Invariance d\u00e9chelle. Des changements d\u00e9tats \u00e0 la turbulence \u00c0 ce sujet, quapporte la coop\u00e9ration entre les marques, leurs r\u00e9seaux et les distributeurs, pourquoi est-ce un enjeu, un levier? mercredi 7 novembre, de 14h \u00e0 16h:Alignement de donn\u00e9es pour figurer sur la liste dadresses, envoyer un message John Szczepaniak, Hardcore Gaming 101, 15 janvier 2011 Inscrivez-vous \u00e0 notre newsletter afin de b\u00e9n\u00e9ficier de 5 sur votre premi\u00e8re commande! \"rencontre On Saturday, Curatorial talk by Aliocha Imoff Kantuta Quiros, at Zurich University of the Arts On pr\u00e9sentera une m\u00e9thode de faisceau pour la minimisation de fonctions non diff\u00e9rentiables et non convexes, puis on lappliquera \u00e0 des probl\u00e8mes doptimisation de lois de commande structur\u00e9es issus de lindustrie a\u00e9ronautique. Ici loi de commande structur\u00e9e fait r\u00e9f\u00e9rence \u00e0 une architecture de contr\u00f4le, qui se compose d\u00e9l\u00e9ments comme les PIDs, combin\u00e9s avec des filtres vari\u00e9s, et comprenant beaucoup moins de param\u00e8tres de r\u00e9glage quun contr\u00f4leur dordre plein pr\u00e9sentant le m\u00eame nombre d\u00e9tats que le syst\u00e8me \u00e0 commander. Les m\u00e9thodes de faisceau utilisent un oracle qui, en chaque it\u00e9r\u00e9, retourne la valeur de lobjectif et un sous-gradient de Clarke arbitraire. Autrement dit loracle fournit une tangente de lobjectif. Afin de g\u00e9n\u00e9rer un pas de descente de qualit\u00e9 \u00e0 partir de lit\u00e9r\u00e9 s\u00e9rieux courant, ces techniques stockent et accumulent de linformation variationnelle, Vous \u00eates tous convi\u00e9s \u00e0 participer \u00e0 cette manifestation et \u00e0 pr\u00e9senter une communication. Une occasion de d\u00e9couvrir la musique de Pascale Criton avec un dispositif sensoriel rare: \u00e9coute sonotactile. \"rencontre \"rencontre Congr\u00e8s pluridisciplinaire Environnement cotier \u00e0 Vannes-.<\/p>\n","protected":false},"excerpt":{"rendered":"

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