{"id":76,"date":"2019-01-10T22:50:14","date_gmt":"2019-01-10T21:50:14","guid":{"rendered":"https:\/\/davidlannes.wordpress.com\/?p=76"},"modified":"2019-01-10T22:50:14","modified_gmt":"2019-01-10T21:50:14","slug":"mathocean","status":"publish","type":"post","link":"https:\/\/david-lannes.perso.math.cnrs.fr\/?p=76","title":{"rendered":"Mathocean du 21\/01\/19"},"content":{"rendered":"\n<h4 class=\"wp-block-heading\">(Bordeaux, salle 2 de l&rsquo;IMB) <\/h4>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>14h00-15h00 Nicolas Barral (Imperial College London)<\/strong> : <em>Framework       pour des simulations c\u00f4ti\u00e8res avec adaptation de maillage       anisotrope<\/em><\/li><li><strong>15h00-16h00 Kevin Martins (EPOC)<\/strong>: <em>Wave transformation in the       surf zone: new insights from 2D LiDAR scanners<\/em><\/li><\/ul>\n\n\n\n<p style=\"text-align:left;\" class=\"has-small-font-size\"><strong>Nicolas Barral: Framework pour des simulations c\u00f4ti\u00e8res avec         adaptation de maillage&nbsp; anisotrope. <\/strong>La plupart des simulations num\u00e9riques pour l&rsquo;ing\u00e9nierie marine       requi\u00e8rent la mod\u00e9lisation de larges zones g\u00e9ographiques, alors que la quantit\u00e9 d&rsquo;int\u00e9r\u00eat est tr\u00e8s localis\u00e9e (par exemple les syst\u00e8mes de g\u00e9n\u00e9ration d&rsquo;\u00e9nergie mar\u00e9motrice, ou l&rsquo;\u00e9tude de       l&rsquo;impact de tsunamis sur des zones habit\u00e9es ou \u00e0 risque). La taille des domaines consid\u00e9r\u00e9s, combin\u00e9e \u00e0 la haute pr\u00e9cision requise conduisent g\u00e9n\u00e9ralement \u00e0 des simulations tr\u00e8s co\u00fbteuses en temps de calcul.       <br>L&rsquo;adaptation de maillage a d\u00e9montr\u00e9 depuis une vingtaine d&rsquo;ann\u00e9es son efficacit\u00e9 pour am\u00e9liorer la pr\u00e9cision num\u00e9rique tout en r\u00e9duisant le temps de calcul en permettant un contr\u00f4le fin de la r\u00e9partition des degr\u00e9s de libert\u00e9. En particulier, l&rsquo;adaptation de maillage anisotrope tire parti de la flexibilit\u00e9 des maillages non structur\u00e9s, et permet d&rsquo;optimiser \u00e0 la fois la taille et l&rsquo;orientation des \u00e9l\u00e9ments du maillage. La g\u00e9n\u00e9ration de ces maillages adapt\u00e9s est bas\u00e9e sur des champs de m\u00e9triques Riemanniennes, eux-m\u00eame d\u00e9riv\u00e9s d&rsquo;un estimateur d&rsquo;erreur, a priori ou a posteriori. La construction de cet estimateur d&rsquo;erreur, propre au mod\u00e8le \u00e9tudi\u00e9, est essentiel au processus d&rsquo;adaptation. Dans cette pr\u00e9sentation, on consid\u00e8re des m\u00e9triques \u00ab\u00a0multi-\u00e9chelles\u00a0\u00bb bas\u00e9e sur la Hessienne des champs de solution, qui sont capables de capturer les diff\u00e9rentes \u00e9chelles des dynamiques oc\u00e9aniques et des structures d&rsquo;ing\u00e9nierie \u00e9tudi\u00e9es.       <br>L&rsquo;efficacit\u00e9 de ces estimateurs d&rsquo;erreur peut \u00eatre consid\u00e9rablement am\u00e9lior\u00e9e en consid\u00e9rant des approches dites \u00ab\u00a0goal oriented\u00a0\u00bb, qui sont en cours de d\u00e9veloppement dans notre       framework: en consid\u00e9rant l&rsquo;adjoint de la solution dans le mod\u00e8le d&rsquo;erreur, seuls les ph\u00e9nom\u00e8nes physiques ayant une influence sur une certaine quantit\u00e9 cible sont maill\u00e9es et r\u00e9solues avec pr\u00e9cision.       <br>Dans cet expos\u00e9, je pr\u00e9senterai l&rsquo;impl\u00e9mentation d&rsquo;un framework permettant de r\u00e9aliser de telles simulations adaptatives dans notre code de simulations c\u00f4ti\u00e8res Thetis, s&rsquo;appuyant sur son int\u00e9gration sous-jacente avec PETSc. On consid\u00e9ra des applications pour la mod\u00e9lisation de la propagation de tsunamis, ainsi que la mod\u00e9lisation de structures de g\u00e9n\u00e9rations d&rsquo;\u00e9nergie mar\u00e9motrice (barrages ou turbines).     <\/p>\n\n\n\n<p style=\"text-align:left;\" class=\"has-small-font-size\"><strong>Kevin Martins: Wave transformation in the surf zone: new         insights from 2D LiDAR scanners: <\/strong>Over the last few decades, remote-sensing technology became an       essential tool for improving our understanding of nearshore       processes. Very recently, the application of lidar scanners (Light       Detection And Ranging) to study swash zone hydrodynamics and       morphodynamics was made possible thanks to the initiatives of few       researchers. In this talk, I will present my PhD work, in which we       explore the use of 2D lidar scanners to monitor the time-varying       surface elevation of breaking waves in the surf zone. The surf       zone constitutes one of the most challenging environments where to       deploy instruments, due to the energetic wave conditions often       found there. Hence, obtaining direct measurements of wave profiles       at a high sampling rate represents a unique opportunity to better       understand wave transformation in the surf zone.<br>In the first part, I will describe the working principles of 2D       lidar scanners, and its potential applications to study nearshore       hydro- and morphodynamics. In a second part, we use an innovative       laboratory dataset to validate a CFD model of breaking wave in a       wave flume at prototype scale (BARDEXII experiments). This       numerical model is used to study and quantify the influence of       wave reflection, generated at the inner surf\/swash zone boundary,       on surf zone hydrodynamics at various temporal scales. Then, the       main field experiments performed during my PhD is presented. An       array of three lidar scanners was deployed from a nearshore pier       at Saltburn-by-the-Sea (UK) to monitor waves from the shoaling       area and up to the runup limit. New insights on individual wave       properties at breaking and on energy dissipation rates in the       inner surf zone were obtained and will be presented. I will       conclude by briefly describing my current work and how lidar data       can be used to improve the parameterizations of physical processes       in the surf zone. <\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>(Bordeaux, salle 2 de l&rsquo;IMB) 14h00-15h00 Nicolas Barral (Imperial College London) : Framework pour des simulations c\u00f4ti\u00e8res avec adaptation de maillage anisotrope 15h00-16h00 Kevin Martins (EPOC): Wave transformation in the surf zone: new insights from 2D LiDAR scanners Nicolas Barral: Framework pour des simulations c\u00f4ti\u00e8res avec adaptation de maillage&nbsp; anisotrope. La plupart des simulations num\u00e9riques [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-76","post","type-post","status-publish","format-standard","hentry","category-mathocean"],"_links":{"self":[{"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=\/wp\/v2\/posts\/76","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=76"}],"version-history":[{"count":0,"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=\/wp\/v2\/posts\/76\/revisions"}],"wp:attachment":[{"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=76"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=76"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/david-lannes.perso.math.cnrs.fr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=76"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}