{"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":[],"acf":[],"custom_fields":[{"0":{"_wp_page_template":["default"],"_bbp_forum_id":["27796"],"_bbp_author_ip":["23.56.168.180"],"_bbp_last_active_time":["1-24-2023  20:20:04"],"_btv_view_count":["4892"],"siebel_km_number":["2039847"],"product_version":["16"],"km_published_date":["2015-08-05T22:26:05.000Z"],"family":["Fluid Dynamics"],"application_name":["FLUENT"]},"test":"articlesansys-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/161683","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/161683\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/media?parent=161683"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}