{"id":161683,"date":"2023-01-25T07:16:40","date_gmt":"2023-01-25T07:16:40","guid":{"rendered":"\/knowledge\/forums\/topic\/what-can-we-do-if-the-turbulence-viscosity-ratio-increases-to-a-large-number-or-even-reaches-the-limit\/"},"modified":"2023-07-31T12:35:42","modified_gmt":"2023-07-31T12:35:42","slug":"what-can-we-do-if-the-turbulence-viscosity-ratio-increases-to-a-large-number-or-even-reaches-the-limit","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/what-can-we-do-if-the-turbulence-viscosity-ratio-increases-to-a-large-number-or-even-reaches-the-limit\/","title":{"rendered":"What can we do if the turbulence viscosity ratio increases to a large number or even reaches the limit?"},"content":{"rendered":"<p>The possible causes for large turbulent viscosity ratio include: &#8211; Bad initial conditions for the turbulence quantities (k and e) &#8211; Improper turbulent boundary conditions &#8211; Skewed cells If the problem is not caused by bad mesh, then the onset of the phenomena can usually be avoided by: -Turn off solving turbulence equations for the first 100-200 iterations -Turn on turbulence and continue iterations If the problem occurs in the midst of the iteration process, then use the following procedure: &#8211; Stop the iteration &#8211; Turn off all equations except the turbulence equations &#8211; Increase turbulence URFs (k and e) to 1 and iterate for 20-50 iterations &#8211; Turn back all equations and reduce the turbulence URFs to 0.5-0.8 and then continue iterations &#8211; Repeat the above steps for several times For faster convergence, it might be useful to obtain an initial solution with the standard k-e model before switching to a more advanced turbulence model. Because some turbulent flows are inherently unsteady, verify if the flow has any unsteady behavior and switch to transient calculation if needed.<\/p>\n","protected":false},"template":"","class_list":["post-161683","topic","type-topic","status-publish","hentry","topic-tag-4424","topic-tag-convergence-problems","topic-tag-fluent","topic-tag-fluid-dynamics","topic-tag-turbulence"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"The possible causes for large turbulent viscosity ratio include: - Bad initial conditions for the turbulence quantities (k and e) - Improper turbulent boundary conditions - Skewed cells If the problem is not caused by bad mesh, then the onset of the phenomena can usually be avoided by: -Turn off solving turbulence equations for the\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" 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