{"id":381300,"date":"2024-09-02T06:40:03","date_gmt":"2024-09-02T06:40:03","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/"},"modified":"2024-09-02T06:40:03","modified_gmt":"2024-09-02T06:40:03","slug":"381300","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/","title":{"rendered":"Reply To: Convergence issue in pipe flow"},"content":{"rendered":"<p>&lt;p&gt;Why are you running the simulations in transient? What did you use as an initial condition? It is always good practice to start from a converged steady-state solution to &#8220;help&#8221; the solver find the correct solution.&lt;\/p&gt;&lt;p&gt;My first guess is that the 0.5 [s] is too large a time step to capture any unsteadiness in the higher velocity case.&nbsp; Compare the velocity profiles from two different times. Where are the areas where there are significant differences? If you were to decrease the time step size, you may be able to better capture the unsteadiness. Yes laminar flows can be unsteady. &lt;\/p&gt;&lt;p&gt;Think back to y = sin(x) . If you have too big a step in x then you won&#8217;t recoginze the curve that appears. A similar thing happens when solving an unsteady problem. We and the solver need to be able to resolve the unsteadiness by decreasing Dt.&nbsp;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-381300","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=\"Why are you running the simulations in transient? What did you use as an initial condition? It is always good practice to start from a converged steady-state solution to &quot;help&quot; the solver find the correct solution.My first guess is that the 0.5 [s] is too large a time step to capture any unsteadiness in the\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/\" \/>\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: Convergence issue in pipe flow | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"Why are you running the simulations in transient? What did you use as an initial condition? It is always good practice to start from a converged steady-state solution to &quot;help&quot; the solver find the correct solution.My first guess is that the 0.5 [s] is too large a time step to capture any unsteadiness in the\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2024-09-02T06:40:03+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2024-09-02T06:40:03+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"Reply To: Convergence issue in pipe flow | Ansys Learning Forum\" \/>\n\t\t<meta name=\"twitter:description\" content=\"Why are you running the simulations in transient? What did you use as an initial condition? It is always good practice to start from a converged steady-state solution to &quot;help&quot; the solver find the correct solution.My first guess is that the 0.5 [s] is too large a time step to capture any unsteadiness in the\" \/>\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\\\/381300\\\/#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\\\/381300\\\/#listItem\",\"name\":\"Reply To: Convergence issue in pipe flow\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/381300\\\/#listItem\",\"position\":2,\"name\":\"Reply To: Convergence issue in pipe flow\",\"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\\\/381300\\\/#webpage\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/reply\\\/381300\\\/\",\"name\":\"Reply To: Convergence issue in pipe flow | Ansys Learning Forum\",\"description\":\"Why are you running the simulations in transient? What did you use as an initial condition? 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It is always good practice to start from a converged steady-state solution to \"help\" the solver find the correct solution.My first guess is that the 0.5 [s] is too large a time step to capture any unsteadiness in the","canonical_url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"BreadcrumbList","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/#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\/381300\/#listItem","name":"Reply To: Convergence issue in pipe flow"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/#listItem","position":2,"name":"Reply To: Convergence issue in pipe flow","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\/381300\/#webpage","url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/","name":"Reply To: Convergence issue in pipe flow | Ansys Learning Forum","description":"Why are you running the simulations in transient? 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What did you use as an initial condition? It is always good practice to start from a converged steady-state solution to &quot;help&quot; the solver find the correct solution.My first guess is that the 0.5 [s] is too large a time step to capture any unsteadiness in the","og:url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/381300\/","article:published_time":"2024-09-02T06:40:03+00:00","article:modified_time":"2024-09-02T06:40:03+00:00","twitter:card":"summary_large_image","twitter:title":"Reply To: Convergence issue in pipe flow | Ansys Learning Forum","twitter:description":"Why are you running the simulations in transient? What did you use as an initial condition? 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