{"id":3849,"date":"2018-02-22T11:57:34","date_gmt":"2018-02-22T10:57:34","guid":{"rendered":"http:\/\/wp.unil.ch\/risk\/?p=3849"},"modified":"2018-02-22T11:57:34","modified_gmt":"2018-02-22T10:57:34","slug":"emmanuel-wyser-investigations-phenomenologiques-et-numeriques-de-limpact-de-gouttes-deau-sur-un-milieu-granulaire-et-du-processus-de-diffusion","status":"publish","type":"post","link":"https:\/\/wp.unil.ch\/risk\/emmanuel-wyser-investigations-phenomenologiques-et-numeriques-de-limpact-de-gouttes-deau-sur-un-milieu-granulaire-et-du-processus-de-diffusion\/","title":{"rendered":"Emmanuel Wyser: Investigations ph\u00e9nom\u00e9nologiques et num\u00e9riques de l&#8217;impact de gouttes d&#8217;eau sur un milieu granulaire et du processus de diffusion"},"content":{"rendered":"<p><em>Emmanuel Wyser<\/em><br \/>\n<em> Director: Prof. Michel Jaboyedoff<\/em><br \/>\n<em> Supervisor: MSc. Benjamin Rudaz<\/em><\/p>\n<p style=\"text-align: justify\">Water erosion phenomenons are increasingly studied and understood but raindrop erosion is&nbsp;far more complex. Raindrop erosion includes subprocesses such as impact, cratering, rim formation,&nbsp;daughter drop splash and soil particle splash. This work is focused on modeling complex&nbsp;ballistic trajectories of soil particle splashes and particle dispersion process. The general purpose&nbsp;is first to recreate the splash effect in laboratory and second to provide optimal numerical&nbsp;models and a better understanding of the soil particle splash.<\/p>\n<p style=\"text-align: justify\">Since the complex multiphase interactions are difficult to model, it is easier to compute&nbsp;numerically the dispersion process. Physical based models are the most common approach in&nbsp;this investigation field. The first assumption is that the crater shape might be the controlling&nbsp;factor in the dispersion process governed by the average splash distance. Moreover, complex&nbsp;physical based models may govern ballistic trajectories. These assumptions have now to be&nbsp;proven.<\/p>\n<p style=\"text-align: justify\">Phenomenological observations are given by experiments in laboratory, on a setup inspired&nbsp;by Furbish et al. (2007) study. Fine soil samples are used in this work and advanced grain&nbsp;size analysis is performed using laser diffraction technique. High-speed camera acquisitions and&nbsp;micro-LiDAR records are used throughout experimental investigations. Then, impact velocities&nbsp;are measured as well as crater shape or particle dispersion. Measured velocities tend to be close&nbsp;to those computed by numerical simulations. High-speed photography analysis shows that the&nbsp;mean initial splash angle is dependent on the drop penetration depth. Moreover, the mean&nbsp;splash angle seems to be dependent on the slope at the crater edge.<\/p>\n<p style=\"text-align: justify\">Numerical computation is then performed to model the dispersion phenomenon. Using a<br \/>\nprobabilistic algorithm, the grain size distribution can be taken into account throughout numerical&nbsp;simulation. The initial splash angle mean value is derived from previous assumption&nbsp;about the key role of the crater shape. Gravity, drag and buoyant forces are also taken into&nbsp;account. Model validation is performed by comparisons between experimental and numerical&nbsp;results using digitalized experimental dispersion photography and LiDAR scanning. Several&nbsp;differences between numerical and empirical results are noticed. The shape of the particle splashing&nbsp;distance distribution is found to be not similar. LiDAR acquisition analysis also shows a&nbsp;non-spherical shape for the crater. But a statistical trend exists for the mean crater gradient -mean splash distance relationship. However this has more to do with dierential initial velocities&nbsp;at the crater&#8217;s edge than with mean splash angle.<\/p>\n<p style=\"text-align: justify\">Further perspectives should be oriented in multiphase interactions ( fluid to soil particle) for&nbsp;a better understanding of the whole phenomenon.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Emmanuel Wyser Director: Prof. Michel Jaboyedoff Supervisor: MSc. Benjamin Rudaz Water erosion phenomenons are increasingly studied and understood but raindrop erosion is&nbsp;far more complex. Raindrop erosion includes subprocesses such as &hellip; <\/p>\n","protected":false},"author":1341,"featured_media":3850,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[73758],"tags":[75171],"class_list":{"0":"post-3849","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-masters_completed","8":"tag-75171"},"_links":{"self":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts\/3849","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/users\/1341"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/comments?post=3849"}],"version-history":[{"count":0,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts\/3849\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/media\/3850"}],"wp:attachment":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/media?parent=3849"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/categories?post=3849"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/tags?post=3849"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}