{"id":55091,"date":"2017-10-17T05:34:19","date_gmt":"2017-10-17T05:34:19","guid":{"rendered":"\/forum\/forums\/reply\/55091\/"},"modified":"2017-10-17T05:34:19","modified_gmt":"2017-10-17T05:34:19","slug":"55091","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/55091\/","title":{"rendered":"Reply To: Speedup simulations of laminar flows with low Reynolds number"},"content":{"rendered":"<p><span style=\"font-family: 'Open Sans', Arial, Helvetica, sans-serif; font-size: 15px;\">You frequently observe that the convergence of the residuals is very good, but the velocity and pressure at monitor points change very slowly on meshes with aspect ratios bigger than 800. This behaviour is caused by the default settings for the ANSYS CFX Solver. The hidden expert parameter: d diffusion option = 3 (1, by default) changes the numerics of the Rhie and Chow algorithm. The effect increases with cell aspect ratio. Note that, as the parameter value of 3 increases the non-linearity, it can cause convergence troubles, e.g. in strong non-Newtonian fluids. Additional keywords: low Re Number, slow convergence<\/span><\/p>\n","protected":false},"template":"","class_list":["post-55091","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"You frequently observe that the convergence of the residuals is very good, but the velocity and pressure at monitor points change very slowly on meshes with aspect ratios bigger than 800. This behaviour is caused by the default settings for the ANSYS CFX Solver. The hidden expert parameter: d diffusion option = 3 (1, by\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/55091\/\" \/>\n\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 4.9.10\" \/>\n\t\t<meta property=\"og:locale\" content=\"en_US\" \/>\n\t\t<meta property=\"og:site_name\" content=\"Ansys Learning Forum | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"Reply To: Speedup simulations of laminar flows with low Reynolds number | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"You frequently observe that the convergence of the residuals is very good, but the velocity and pressure at monitor points change very slowly on meshes with aspect ratios bigger than 800. This behaviour is caused by the default settings for the ANSYS CFX Solver. The hidden expert parameter: d diffusion option = 3 (1, by\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/55091\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2017-10-17T05:34:19+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2017-10-17T05:34:19+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"Reply To: Speedup simulations of laminar flows with low Reynolds number | Ansys Learning Forum\" \/>\n\t\t<meta name=\"twitter:description\" content=\"You frequently observe that the convergence of the residuals is very good, but the velocity and pressure at monitor points change very slowly on meshes with aspect ratios bigger than 800. This behaviour is caused by the default settings for the ANSYS CFX Solver. The hidden expert parameter: d diffusion option = 3 (1, by\" \/>\n\t\t<script type=\"application\/ld+json\" class=\"aioseo-schema\">\n\t\t\t{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/55091\\\/#breadcrumblist\",\"itemListElement\":[{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/55091\\\/#listItem\",\"name\":\"Reply To: Speedup simulations of laminar flows with low Reynolds number\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/55091\\\/#listItem\",\"position\":2,\"name\":\"Reply To: Speedup simulations of laminar flows with low Reynolds number\",\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"name\":\"Home\"}}]},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#organization\",\"name\":\"Ansys Learning Forum\",\"description\":\"Ansys Innovation Space\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/55091\\\/#webpage\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/55091\\\/\",\"name\":\"Reply To: Speedup simulations of laminar flows with low Reynolds number | Ansys Learning Forum\",\"description\":\"You frequently observe that the convergence of the residuals is very good, but the velocity and pressure at monitor points change very slowly on meshes with aspect ratios bigger than 800. This behaviour is caused by the default settings for the ANSYS CFX Solver. 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