{"id":13401,"date":"2022-11-08T14:36:13","date_gmt":"2022-11-08T13:36:13","guid":{"rendered":"https:\/\/www.univ-smb.fr\/locie\/?p=13401"},"modified":"2022-11-08T14:37:22","modified_gmt":"2022-11-08T13:37:22","slug":"mercredi-05-octobre-a-9h00-these-de-arnat-mahamoudou-2","status":"publish","type":"post","link":"https:\/\/www.univ-smb.fr\/locie\/2022\/11\/08\/mercredi-05-octobre-a-9h00-these-de-arnat-mahamoudou-2\/","title":{"rendered":"jeudi 24 novembre, \u00e0 14h00 – Th\u00e8se de Misa Ishimura"},"content":{"rendered":"

Soutenance de th\u00e8se –\u00a0 Misa Ishimura
\n<\/strong><\/span><\/h2>\n

jeudi 24 novembre<\/strong>, \u00e0 14h00<\/strong>, au Laboratoire FAST (<\/strong>Universit\u00e9 Paris-Saclay<\/strong>) <\/strong>dans le Petit Amphith\u00e9\u00e2tre<\/strong> du B\u00e2timent\u00a0Pascal (B\u00e2t. 530)<\/strong>.<\/span><\/h3>\n

Films liquides tombants cisaillement par un \u00e9coulement turbulent de gaz \u00e0 contre-courant confin\u00e9: stabilit\u00e9, mod\u00e9lisation et exp\u00e9riences<\/span><\/span><\/strong><\/h3>\n

\u00a0<\/span><\/b><\/h2>\n
\n

R\u00e9sum\u00e9<\/strong><\/span><\/h3>\n
Gravity-driven falling liquid films are known to develop large-amplitude surface waves due to the<\/span><\/span><\/span> long-wave Kapitza instability. In many applications, such as cryogenic air separation in rectification columns,<\/span> a falling liquid film is put into contact with a turbulent counter-current gas flow within a strongly confined<\/span> geometry. In this case, surface waves greatly enhance inter-phase mass transfer, but, through their interaction<\/span> with the gas, they can also trigger critical events (obstruction of the channel, upward travelling waves, liquid<\/span> arrest). To identify optimal wavy-film regimes that reconcile these two opposing effects, it is important to<\/span> elucidate the linear and nonlinear hydrodynamic response of the wavy falling liquid film to the gas flow.<\/span><\/span> <\/span><\/span><\/div>\n
We have studied this problem based on a prototype configuration: a liquid film falling in a weakly-inclined<\/span> channel of height H*=10 mm and sheared by a counter-current turbulent gas flow. On the one<\/span> hand, we have performed experiments in a setup allowing to visualize and measure the spatio-temporal<\/span> evolution of surface waves under the effect of an increasingly strong gas flow. On the other hand, we have<\/span> developed a low-dimensional long-wave model based on the weighted residual integral boundary layer<\/span> (WRIBL) approach and a Reynolds-averaged description of turbulence in the gas. Thirdly, we have performed<\/span> linear stability calculations based on the full governing equations, allowing to identify the different long- and<\/span> short-wave instability modes, as well as the transition from convective to absolute instability (AI).<\/span><\/span>
The low-dimensional model has been validated with our experiments. It accurately predicts the effect of a<\/span> turbulent counter-current gas flow on the frequency and growth rate of the linearly most-amplified waves,<\/span>
including the onset of AI. And, it accurately captures the gas-effect on the height and shape of nonlinear surface<\/span> waves.<\/span><\/span>
Moreover, we have uncovered several physical phenomena. Firstly, depending on the inclination angle, we<\/span> find<\/span> that<\/span> the<\/span> turbulent<\/span> counter-current<\/span> gas<\/span> flow<\/span> can<\/span> render<\/span> the<\/span> falling<\/span> film<\/span> unconditionally<\/span> stable,<\/span> unconditionally unstable or subject to stability islands linked to the laminar\/turbulent transition. Secondly, we<\/span> find that the gas flow disrupts the spatio-temporal coherence of nonlinear wave trains by precipitating<\/span>
coalescence events and the emergence of dangerous large-amplitude tsunami waves (TW) that grow<\/span> indefinitely by absorbing smaller waves in their path. This dynamics is much faster and violent than the<\/span>
coarsening dynamics observed in a quiescent gas.<\/span><\/span>
Thirdly, we find that transgressing the gas-induced AI limit of the Kapitza instability is not necessarily<\/span> dangerous. On the contrary, the temporal growth associated with AI can lead to a narrow and effective linear<\/span> wave selection near the liquid inlet. Once these waves enter the weakly-nonlinear regime, they propagate<\/span> downstream in the form of a very regular train of limited-amplitude solitary waves, thus avoiding dangerous<\/span> TW. This wave train is robust w.r.t. ambient noise. However, it can be disrupted by applying a strong<\/span> monochromatic inlet forcing of competing frequency. In that case, coalescence-induced TW form once again<\/span> and interact with almost-standing ripples emerging from AI on the thin residual film.<\/span><\/span>
Fourthly, we have uncovered a new turbulence-induced short-wave interfacial instability mode associated with<\/span> a negative wave velocity, which becomes dominant beyond the long-wave AI limit, but well below the<\/span> threshold of the Tollmien-Schlichting instability. This finding allows to explain, at last, the occurrence of<\/span> short-wave upward-travelling ripples observed in previous experiments. Our linear stability calculations<\/span> accurately predict the wave speed and wave length of these ripples as compared to our own experiments. Also,<\/span> we find that the short- and long-wave instability modes merge when the counter-current gas flow rate is large.<\/span><\/span><\/span><\/div>\n<\/div>\n

Composition du jury<\/strong><\/span><\/h3>\n

Pierre-Yves LAGR\u00c9E (Rapporteur), <\/strong>Directeur de recherche CNRS, Institut d’Alembert, Universit\u00e9 Pierre et Marie Curie<\/p>\n

Ranga NARAYANAN (Rapporteur), <\/strong>Professeur, Chemical Engineering dpt, University of Florida<\/p>\n

Cathy CASTELAIN, <\/strong>Directrice de recherche CNRS, LTeN, Universit\u00e9 de Nantes<\/p>\n

S\u00e9verine MILLET, <\/strong>Ma\u00eetresse de conf\u00e9rences, LMFA, Universit\u00e9 de Lyon 1<\/p>\n

Gianluca LAVALLE, <\/strong>Ma\u00eetre assistant, Ecole des Mines de Saint-Etienne<\/p>\n

Sophie MERGUI (Co-encadrant), <\/strong>Ma\u00eetresse de conferences, FAST, Universite Pierre et Marie Curie<\/p>\n

Georg DIETZE (Co-directeur de th\u00e8se), <\/strong>Charg\u00e9 de recherche CNRS, FAST, Universit\u00e9 Paris-Saclay<\/p>\n

Christian RUYER-QUIL (Directeur de th\u00e8se), <\/strong>Professeur, LOCIE, Universit\u00e9 Savoie Mont Blanc<\/p>\n","protected":false},"excerpt":{"rendered":"

Soutenance de th\u00e8se –\u00a0 Misa Ishimura jeudi 24 novembre, \u00e0 14h00, au Laboratoire FAST (Universit\u00e9 Paris-Saclay) dans le Petit Amphith\u00e9\u00e2tre du B\u00e2timent\u00a0Pascal (B\u00e2t. 530). Films liquides tombants cisaillement par un \u00e9coulement turbulent de gaz \u00e0 […]<\/p>\n","protected":false},"author":141,"featured_media":4761,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","_seopress_robots_follow":"","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"none","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"","_seopress_social_fb_title":"","_seopress_social_fb_desc":"","_seopress_social_fb_img":"","_seopress_social_fb_img_attachment_id":0,"_seopress_social_fb_img_width":0,"_seopress_social_fb_img_height":0,"_seopress_social_twitter_title":"","_seopress_social_twitter_desc":"","_seopress_social_twitter_img":"","_seopress_social_twitter_img_attachment_id":0,"_seopress_social_twitter_img_width":0,"_seopress_social_twitter_img_height":0,"_seopress_redirections_value":"","_seopress_redirections_enabled":"","_seopress_redirections_enabled_regex":"","_seopress_redirections_logged_status":"both","_seopress_redirections_param":"","_seopress_redirections_type":301,"_seopress_analysis_target_kw":"","_seopress_news_disabled":"","_seopress_video_disabled":"","_seopress_video":[],"_seopress_pro_schemas_manual":[],"_seopress_pro_rich_snippets_disable_all":"","_seopress_pro_rich_snippets_disable":[],"_seopress_pro_schemas":[],"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"","_relevanssi_noindex_reason":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[18,56,21],"tags":[],"class_list":["post-13401","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-a-la-une","category-a-venir","category-theses"],"acf":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/www.univ-smb.fr\/locie\/wp-content\/uploads\/sites\/72\/2020\/12\/reportage-recherche-locie-yannick-perrin-77-e1607958891999.jpg","_links":{"self":[{"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/posts\/13401","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/users\/141"}],"replies":[{"embeddable":true,"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/comments?post=13401"}],"version-history":[{"count":2,"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/posts\/13401\/revisions"}],"predecessor-version":[{"id":13407,"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/posts\/13401\/revisions\/13407"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/media\/4761"}],"wp:attachment":[{"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/media?parent=13401"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/categories?post=13401"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.univ-smb.fr\/locie\/wp-json\/wp\/v2\/tags?post=13401"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}