{"id":47571,"date":"2019-11-05T11:26:57","date_gmt":"2019-11-05T10:26:57","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-o-numero-critico-de-reynolds-definicao\/"},"modified":"2020-01-24T10:10:02","modified_gmt":"2020-01-24T09:10:02","slug":"o-que-e-o-numero-critico-de-reynolds-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-numero-critico-de-reynolds-definicao\/","title":{"rendered":"O que \u00e9 o n\u00famero cr\u00edtico de Reynolds &#8211; defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">O n\u00famero cr\u00edtico de Reynolds est\u00e1 associado \u00e0 transi\u00e7\u00e3o laminar-turbulenta, na qual um fluxo laminar se torna turbulento.\u00a0N\u00famero cr\u00edtico de Reynolds<\/div>\n<\/div>\n<div class=\"su-divider su-divider-style-dotted\"><\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2>N\u00famero cr\u00edtico de Reynolds<\/h2>\n<p><strong><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Reynolds-Number.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-14465 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Reynolds-Number-300x151.png\" alt=\"N\u00famero de Reynolds\" width=\"300\" height=\"151\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Reynolds-Number-300x151.png\" \/><\/a>O\u00a0<a title=\"N\u00famero de Reynolds\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/reynolds-number\/\">n\u00famero de Reynolds<\/a><\/strong>\u00a0\u00a0\u00e9 a raz\u00e3o de\u00a0\u00a0<strong>for\u00e7as inerciais<\/strong>\u00a0para\u00a0\u00a0<strong>for\u00e7as\u00a0\u00a0<\/strong><strong>viscosas<\/strong>\u00a0\u00a0e \u00e9 um par\u00e2metro conveniente para prever se uma condi\u00e7\u00e3o de fluxo ser\u00e1\u00a0\u00a0<strong><a title=\"Fluxo Laminar - Fluxo Viscoso\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-laminar-fluxo-viscoso-definicao\/\">laminar<\/a>\u00a0ou\u00a0<a title=\"Fluxo turbulento\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-turbulento-definicao\/\">turbulenta<\/a><\/strong>\u00a0.<\/p>\n<p>O\u00a0<strong>n\u00famero cr\u00edtico de Reynolds<\/strong>\u00a0\u00a0est\u00e1 associado \u00e0\u00a0\u00a0<strong>transi\u00e7\u00e3o laminar-turbulenta,\u00a0<\/strong>\u00a0na qual um fluxo laminar se torna turbulento.\u00a0Esse \u00e9 um processo extraordinariamente complicado, que atualmente n\u00e3o \u00e9 totalmente compreendido.<\/p>\n<h2>N\u00famero cr\u00edtico de Reynolds para fluxo em um tubo<\/h2>\n<p>Para o fluxo em um tubo de di\u00e2metro\u00a0\u00a0<span class=\"texhtml\"><i>D<\/i><\/span>\u00a0, observa\u00e7\u00f5es experimentais mostram que, para o fluxo &#8220;totalmente desenvolvido&#8221;, o n\u00famero cr\u00edtico de Reynolds \u00e9 de\u00a0\u00a0<strong>Re\u00a0<sub>d, crit<\/sub>\u00a0\u00a0= 2300.<\/strong><\/p>\n<ul>\n<li><strong>Fluxo laminar.\u00a0<\/strong>\u00a0Para fins pr\u00e1ticos, se o n\u00famero de Reynolds for\u00a0\u00a0<strong>menor que 2000<\/strong>\u00a0, o fluxo ser\u00e1 laminar.\u00a0O n\u00famero de Reynolds de transi\u00e7\u00e3o aceito para o fluxo em um tubo circular \u00e9\u00a0\u00a0<strong>Re\u00a0<sub>d, crit<\/sub>\u00a0\u00a0= 2300.<\/strong><\/li>\n<li><strong>Fluxo de transi\u00e7\u00e3o.\u00a0<\/strong>\u00a0Nos n\u00fameros de Reynolds\u00a0\u00a0<strong>entre 2000 e 4000,<\/strong>\u00a0\u00a0o fluxo \u00e9 inst\u00e1vel como resultado do in\u00edcio da turbul\u00eancia.\u00a0Esses fluxos \u00e0s vezes s\u00e3o chamados de fluxos de transi\u00e7\u00e3o.<\/li>\n<li><strong>Fluxo turbulento.\u00a0<\/strong>\u00a0Se o n\u00famero de Reynolds for\u00a0\u00a0<strong>maior que 3500<\/strong>\u00a0, o fluxo ser\u00e1 turbulento.<\/li>\n<\/ul>\n<p>Observe que, o n\u00famero cr\u00edtico de Reynolds \u00e9 diferente para cada geometria.<\/p>\n<h2>N\u00famero cr\u00edtico de Reynolds no fluxo da camada limite sobre uma placa plana.<\/h2>\n<div>\n<p>Ao determinar se a camada limite \u00e9 laminar ou turbulenta, \u00e9 freq\u00fcentemente razo\u00e1vel supor que a transi\u00e7\u00e3o comece em algum local\u00a0<strong>x\u00a0<sub>cr\u00edtico<\/sub><\/strong>\u00a0, como mostrado na figura.\u00a0Esta localiza\u00e7\u00e3o \u00e9 determinada pelo n\u00famero cr\u00edtico de Reynolds,\u00a0<strong>Re\u00a0<sub>x, crit<\/sub><\/strong>\u00a0.\u00a0Para o fluxo sobre uma placa plana,<\/p>\n<div>\n<p><strong>a transi\u00e7\u00e3o da<\/strong>\u00a0\u00a0camada limite\u00a0<strong>laminar para a turbulenta<\/strong>\u00a0ocorre quando o n\u00famero de Reynolds em x excede\u00a0\u00a0<strong>Re\u00a0<sub>x, crit<\/sub><\/strong><strong>\u00a0\u00a0~ 500.000<\/strong>\u00a0.\u00a0A transi\u00e7\u00e3o pode ocorrer mais cedo, mas depende principalmente da\u00a0<strong>rugosidade<\/strong>\u00a0da\u00a0\u00a0<strong>superf\u00edcie<\/strong>\u00a0.\u00a0A camada limite turbulenta espessa mais rapidamente do que a camada limite laminar como resultado do aumento da tens\u00e3o de cisalhamento na superf\u00edcie do corpo.<\/p>\n<div><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boundary-layer-on-flat-plate.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-14390 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boundary-layer-on-flat-plate.png\" alt=\"Camada limite na placa plana\" width=\"1025\" height=\"357\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boundary-layer-on-flat-plate.png\" \/><\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div><\/div>\n<div>\n<h2><span>Exemplo: n\u00famero cr\u00edtico de Reynolds<\/span><\/h2>\n<p><span>Uma placa plana longa e fina \u00e9 colocada paralelamente a uma\u00a0\u00a0<\/span><strong><span>de 1 m \/ s<\/span><\/strong><span>\u00a0\u00a0de fluxo de \u00e1gua a\u00a0<\/span><strong><span>\u00a020 \u00b0 C<\/span><\/strong><span>\u00a0.\u00a0Assume-se que a viscosidade cinem\u00e1tica de \u00e1gua a 20 \u00b0 C \u00e9 igual a\u00a0\u00a0<\/span><strong><span>1 x 10\u00a0<\/span><sup><span>-6<\/span><\/sup><span>\u00a0\u00a0m\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0\/ s<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>A\u00a0\u00a0<\/span><strong><span>que dist\u00e2ncia x<\/span><\/strong><span>\u00a0\u00a0da borda anterior estar\u00e1 a\u00a0\u00a0<\/span><strong><span>transi\u00e7\u00e3o<\/span><\/strong><span>\u00a0\u00a0da camada limite laminar para a turbulenta (ou seja, encontre Re\u00a0<\/span><sub><span>x<\/span><\/sub><span>\u00a0\u00a0~ 500.000).<\/span><\/p>\n<p><strong><span>Solu\u00e7\u00e3o:<\/span><\/strong><\/p>\n<p><span>Para localizar a transi\u00e7\u00e3o da camada limite laminar para a turbulenta, precisamos encontrar x em que\u00a0\u00a0<\/span><strong><span>Re\u00a0<\/span><sub><span>x<\/span><\/sub><span>\u00a0\u00a0~ 500.000<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><strong><span>x<\/span><\/strong><span>\u00a0\u00a0= 500 000 x 1 \u00d7 10\u00a0<\/span><sup><span>-6<\/span><\/sup><span>\u00a0\u00a0[m\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0\/ s] \/ 1 [m \/ s] =\u00a0\u00a0<\/span><strong><span>0,5 m<\/span><\/strong><\/p>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div>\n<p>&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;.<\/p>\n<p>Este artigo \u00e9 baseado na tradu\u00e7\u00e3o autom\u00e1tica do artigo original em ingl\u00eas. Para mais informa\u00e7\u00f5es, consulte o artigo em ingl\u00eas. Voc\u00ea pode nos ajudar. Se voc\u00ea deseja corrigir a tradu\u00e7\u00e3o, envie-a para: translations@nuclear-power.com ou preencha o formul\u00e1rio de tradu\u00e7\u00e3o on-line. Agradecemos sua ajuda, atualizaremos a tradu\u00e7\u00e3o o mais r\u00e1pido poss\u00edvel. Obrigado.<\/p>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>O n\u00famero cr\u00edtico de Reynolds est\u00e1 associado \u00e0 transi\u00e7\u00e3o laminar-turbulenta, na qual um fluxo laminar se torna turbulento.\u00a0N\u00famero cr\u00edtico de Reynolds N\u00famero cr\u00edtico de Reynolds O\u00a0n\u00famero de Reynolds\u00a0\u00a0\u00e9 a raz\u00e3o de\u00a0\u00a0for\u00e7as inerciais\u00a0para\u00a0\u00a0for\u00e7as\u00a0\u00a0viscosas\u00a0\u00a0e \u00e9 um par\u00e2metro conveniente para prever se uma condi\u00e7\u00e3o de fluxo ser\u00e1\u00a0\u00a0laminar\u00a0ou\u00a0turbulenta\u00a0. O\u00a0n\u00famero cr\u00edtico de Reynolds\u00a0\u00a0est\u00e1 associado \u00e0\u00a0\u00a0transi\u00e7\u00e3o laminar-turbulenta,\u00a0\u00a0na qual um fluxo laminar &#8230; <a title=\"O que \u00e9 o n\u00famero cr\u00edtico de Reynolds &#8211; defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-numero-critico-de-reynolds-definicao\/\" aria-label=\"More on O que \u00e9 o n\u00famero cr\u00edtico de Reynolds &#8211; defini\u00e7\u00e3o\">Ler mais<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[14],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v15.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>O que \u00e9 o n\u00famero cr\u00edtico de Reynolds - defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"O n\u00famero cr\u00edtico de Reynolds est\u00e1 associado \u00e0 transi\u00e7\u00e3o laminar-turbulenta, na qual um fluxo laminar se torna turbulento. 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