{"id":669,"date":"2008-10-14T04:07:56","date_gmt":"2008-10-14T09:07:56","guid":{"rendered":"http:\/\/arxivblog.com\/?p=669"},"modified":"2008-10-14T04:07:56","modified_gmt":"2008-10-14T09:07:56","slug":"the-waves-beneath-the-sea","status":"publish","type":"post","link":"http:\/\/arxivblog.com\/?p=669","title":{"rendered":"The waves beneath the sea"},"content":{"rendered":"<p><a href=\"http:\/\/arxivblog.com\/wp-content\/uploads\/2008\/10\/dead-water.jpg\" title=\"dead-water.jpg\"><img decoding=\"async\" src=\"http:\/\/arxivblog.com\/wp-content\/uploads\/2008\/10\/dead-water.thumbnail.jpg\" alt=\"dead-water.jpg\" \/><\/a><\/p>\n<p><a href=\"http:\/\/arxivblog.com\/wp-content\/uploads\/2008\/10\/dead-water.jpg\" title=\"dead-water.jpg\"><span style=\"text-decoration: none\"><!--[if gte vml 1]><v:shapetype  id=\"_x0000_t75\" coordsize=\"21600,21600\" o:spt=\"75\" o:preferrelative=\"t\"  path=\"m@4@5l@4@11@9@11@9@5xe\" filled=\"f\" stroked=\"f\">  <v:stroke joinstyle=\"miter\"\/>  <v:formulas>   <v:f eqn=\"if lineDrawn pixelLineWidth 0\"\/>   <v:f eqn=\"sum @0 1 0\"\/>   <v:f eqn=\"sum 0 0 @1\"\/>   <v:f eqn=\"prod @2 1 2\"\/>   <v:f eqn=\"prod @3 21600 pixelWidth\"\/>   <v:f eqn=\"prod @3 21600 pixelHeight\"\/>   <v:f eqn=\"sum @0 0 1\"\/>   <v:f eqn=\"prod @6 1 2\"\/>   <v:f eqn=\"prod @7 21600 pixelWidth\"\/>   <v:f eqn=\"sum @8 21600 0\"\/>   <v:f eqn=\"prod @7 21600 pixelHeight\"\/>   <v:f eqn=\"sum @10 21600 0\"\/>  <\/v:formulas>  <v:path o:extrusionok=\"f\" gradientshapeok=\"t\" o:connecttype=\"rect\"\/>  <o:lock v:ext=\"edit\" aspectratio=\"t\"\/> <\/v:shapetype><v:shape id=\"_x0000_i1025\" type=\"#_x0000_t75\" alt=\"dead-water.jpg\"  title=\"&quot;dead-water.jpg&quot;\" style='width:24pt;height:24pt' o:button=\"t\"\/><![endif]--><!--[if !vml]--><\/span><\/a>Dead water is the curious phenomenon when ships become sluggish and difficult to control in stratified waters in which a fresh layer sits on top of salty water. Such conditions often occur in arctic regions where water run off from melting glaciers or ice flows can float on top of denser salty water.<\/p>\n<p>The effect was first noted by the Norwegian explorer Fridtjof Nansen in 1893 who noted that while his boat, Fram, could cruise easily at 7 knots in ordinary seas, in dead water she was unable to make 1.5 knots. &#8220;When caught in dead water Fram appeared to be held back, as if by some mysterious force,&#8221; he wrote.<\/p>\n<p>Now Romain Vasseur and pals from the <st1:placetype w:st=\"on\">University<\/st1:placetype> of <st1:placename w:st=\"on\">Lyon<\/st1:placename> in <st1:country-region w:st=\"on\"><st1:place w:st=\"on\">France<\/st1:place><\/st1:country-region> show how the effect is even more pronounced when three layers of water are involved: a fresh layer sitting on a salty layer sitting an even saltier layer.<\/p>\n<p>They have even made <a href=\"http:\/\/ecommons.library.cornell.edu\/bitstream\/1813\/11470\/3\/VasseurMercierDauxois_mpeg1_APS2008.mpg\">a rather beautiful video showing how a toy boat is dramatically slowed by the effect.<\/a><\/p>\n<p>The explanation is that movement of the boat causes a wave to form beneath the surface at the interface between the fresh and salty waters. This wave eventually catches up with the boat and breaks, dragging the boat to a halt.<\/p>\n<p>What&#8217; s fascinating is that while all this is going on beneath the water, the surface remains absolutely flat.<\/p>\n<p>Presumably these guys have posted this paper in anticipation of the Gallery of Fluid Motion 2008 at the upcoming <a href=\"http:\/\/www.aps.org\/units\/dfd\/meetings\/meeting.cfm?name=DFD08\">meeting of the APS Division of Fluid Dynamics <\/a>in San Antonio in November.<\/p>\n<p>Ref: <a href=\"http:\/\/arxiv.org\/abs\/0810.1702\">arxiv.org\/abs\/0810.1702<\/a>: Dead Waters: Large Amplitude Interfacial Waves Generated by a Boat in a Stratified Fluid<\/p>\n<p class=\"MsoNormal\"><span lang=\"EN-GB\"><o:p>\u00a0<\/o:p><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Dead water is the curious phenomenon when ships become sluggish and difficult to control in stratified waters in which a fresh layer sits on top of salty water. Such conditions often occur in arctic regions where water run off from melting glaciers or ice flows can float on top of denser salty water. The effect [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,17],"tags":[],"class_list":["post-669","post","type-post","status-publish","format-standard","hentry","category-mean-machines","category-slimey-stuff"],"_links":{"self":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/posts\/669","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=669"}],"version-history":[{"count":0,"href":"http:\/\/arxivblog.com\/index.php?rest_route=\/wp\/v2\/posts\/669\/revisions"}],"wp:attachment":[{"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=669"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=669"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/arxivblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=669"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}