{"id":161699,"date":"2023-01-25T07:16:44","date_gmt":"2023-01-25T07:16:44","guid":{"rendered":"\/knowledge\/forums\/topic\/why-is-the-courant-number-specified-for-an-implicit-time-marching-scheme-when-the-time-step-size-is-already-an-input\/"},"modified":"2023-07-31T12:35:44","modified_gmt":"2023-07-31T12:35:44","slug":"why-is-the-courant-number-specified-for-an-implicit-time-marching-scheme-when-the-time-step-size-is-already-an-input","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/why-is-the-courant-number-specified-for-an-implicit-time-marching-scheme-when-the-time-step-size-is-already-an-input\/","title":{"rendered":"Why is the Courant number specified for an implicit time marching scheme when the time step size is already an input?"},"content":{"rendered":"<p>The implicit time marching method is a &#8220;dual&#8221; time formulation, which implies that the marching is done in physical time as well as in &#8220;pseudo&#8221; time. The &#8220;pseudo&#8221; time marching, also known as &#8220;inner iterations&#8221;, is performed to advance the solution from one physical time to the next physical time. The next physical time is given by the current physical time plus the user specified time step size.  The &#8220;pseudo&#8221; time step size used for these &#8220;inner iterations&#8221; are calculated using the Courant number based on the stability theory. The Courant number is specified in the Solution Controls panel.  The number of &#8220;inner iterations&#8221; performed depend on the &#8220;max. iterations per time step&#8221; parameter specified in the Solution> run calculation panel and the convergence criteria for residuals set in the monitors panel.<\/p>\n","protected":false},"template":"","class_list":["post-161699","topic","type-topic","status-publish","hentry","topic-tag-4457","topic-tag-fluent","topic-tag-fluid-dynamics","topic-tag-general","topic-tag-general-fluent"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"The implicit time marching method is a &quot;dual&quot; time formulation, which implies that the marching is done in physical time as well as in &quot;pseudo&quot; time. The &quot;pseudo&quot; time marching, also known as &quot;inner iterations&quot;, is performed to advance the solution from one physical time to the next physical time. The next physical time is\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/why-is-the-courant-number-specified-for-an-implicit-time-marching-scheme-when-the-time-step-size-is-already-an-input\/\" \/>\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 Knowledge | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"Why is the Courant number specified for an implicit time marching scheme when the time step size is already an input? | Ansys Knowledge\" \/>\n\t\t<meta property=\"og:description\" content=\"The implicit time marching method is a &quot;dual&quot; time formulation, which implies that the marching is done in physical time as well as in &quot;pseudo&quot; time. The &quot;pseudo&quot; time marching, also known as &quot;inner iterations&quot;, is performed to advance the solution from one physical time to the next physical time. The next physical time is\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/why-is-the-courant-number-specified-for-an-implicit-time-marching-scheme-when-the-time-step-size-is-already-an-input\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2023-01-25T07:16:44+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2023-07-31T12:35:44+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"Why is the Courant number specified for an implicit time marching scheme when the time step size is already an input? | Ansys Knowledge\" \/>\n\t\t<meta name=\"twitter:description\" content=\"The implicit time marching method is a &quot;dual&quot; time formulation, which implies that the marching is done in physical time as well as in &quot;pseudo&quot; time. The &quot;pseudo&quot; time marching, also known as &quot;inner iterations&quot;, is performed to advance the solution from one physical time to the next physical time. 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