{"id":44158,"date":"2020-05-19T15:48:34","date_gmt":"2020-05-19T15:48:34","guid":{"rendered":"\/forum\/forums\/topic\/turbulent-viscosity-ratio-limited-in-external-aerodynamics\/"},"modified":"2020-05-19T15:48:34","modified_gmt":"2020-05-19T15:48:34","slug":"turbulent-viscosity-ratio-limited-in-external-aerodynamics","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/turbulent-viscosity-ratio-limited-in-external-aerodynamics\/","title":{"rendered":"Turbulent Viscosity Ratio Limited in External Aerodynamics"},"content":{"rendered":"<p>Hi there,<br \/>I am doing an external aerodynamics simulation of a 3D model of a train under crosswind (cross-flow) effect. The mesh is hybrid and consists of a big hexahedral domain, and a smaller box inside the domain (around the train) containing tetrahedral and prism mesh that was generated using ICEM CFD. Minimum orthogonal quality is 0.05. Minimum quality criterion based on ICEM CFD is 0.1. Fluent case check has no recomendation in terms of mesh quality so far. Total elements are around 7M, and I am trying to keep it below 8M because of my hardware limitation.<\/p>\n<p><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/us.v-cdn.net\/6032193\/uploads\/attachments\/91eb8b86-89f8-4bb0-b4d4-ab6a00509dcc\/d320aa20-ac42-47ed-8345-abc001090f20_messageimage-1589176948107.jpg?width=690&amp;upscale=false\" alt=\"Big Domain and mesh quality\" width=\"724\" height=\"407\"><\/p>\n<p><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/us.v-cdn.net\/6032193\/uploads\/attachments\/91eb8b86-89f8-4bb0-b4d4-ab6a00509dcc\/5e0469a3-0428-4e32-8c34-abc001093530_smaller-domain.jpg?width=690&amp;upscale=false\" alt=\"smaller box surrounding the train\" width=\"496\" height=\"236\"><\/p>\n<p><\/p>\n<p>Boundary conditions are as follows:<br \/>front: inlet 44m\/s, 1% turb intensity, 0.05 length scale<br \/>left: inlet 20m\/s, 1% turb intensity, 0.02 length scale<br \/>right: pressure out, 0Pa, 1% backflow, 0.02 length scale<br \/>back: pressure out, 0Pa, 1% backflow, 0.05 length scale<br \/>top: symmetry<br \/>bottom: moving wall 44m\/s, specified shear=0<\/p>\n<p><\/p>\n<p>The calculation was first initialized by using first order k omega SST up to 500 iterations. After that, I switched to transient second order. I started to see message saying that turbulent viscosity limited to viscosity ratio of 1e+5 after around 250steps. The number of cells are increasing with every time steps, no sign of decreasing after around 200 steps. The time step size is 1e-3, and there are 30 iterations per time step.<\/p>\n<p><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/us.v-cdn.net\/6032193\/uploads\/attachments\/91eb8b86-89f8-4bb0-b4d4-ab6a00509dcc\/358c27cb-1927-43d2-b815-abc0010965c0_turbulent-viscoisity-ratio-steady-simple-44-20-second-643-turb-lim-po-blkg-70-kanan-0.jpg?width=690&amp;upscale=false\" alt=\"turbulent viscosity ratio limited\" width=\"463\" height=\"272\"><\/p>\n<p><\/p>\n<p>Can anybody please enlighten me on how to solve the turbulent viscosity limited problem? Did I miss something in my fluent settings or my mesh quality might be the problem?<\/p>\n<p><\/p>\n<p>Thanks,<br \/>Tim.<\/p>\n","protected":false},"template":"","class_list":["post-44158","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["16339"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["publish"],"_bbp_author_ip":[null],"_bbp_old_sticky_status_id":["normal"],"_bbp_likes_count":["0"],"_btv_view_count":["1762"],"_bbp_subscription":["247822"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["44158"],"_bbp_forum_id":["27792"],"_bbp_engagement":["59","173577"],"_bbp_voice_count":["2"],"_bbp_reply_count":["2"],"_bbp_last_reply_id":["115165"],"_bbp_last_active_id":["115165"],"_bbp_last_active_time":["2020-05-20 15:58:02"]},"test":"tim13"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/44158","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/44158\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=44158"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}