{"id":295681,"date":"2023-07-31T14:45:14","date_gmt":"2023-07-31T14:45:14","guid":{"rendered":"\/forum\/forums\/topic\/time-step-determination-for-les-based-case\/"},"modified":"2023-07-31T14:45:14","modified_gmt":"2023-07-31T14:45:14","slug":"time-step-determination-for-les-based-case","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/time-step-determination-for-les-based-case\/","title":{"rendered":"Time-step determination for LES based case"},"content":{"rendered":"<p class=\"MsoNormal\">Hi everyone,<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\">I have some doubts regarding time step calculations and i am using <strong>CFL = (u * <span>&Delta;<\/span>t\/<span>&Delta;<\/span>x)<\/strong> formular. I use <strong>CFL <\/strong>number as <em>1<\/em> , for <strong>u <\/strong>i&nbsp;am using <em>383.9 m\/s<\/em> but <strong><span>&Delta;<\/span>x<\/strong> is what confusing me. According to some resources <strong><span>&Delta;<\/span>x<\/strong> represent the meaning of ,<span style=\"text-decoration: underline\">characteristic length<\/span>, <span style=\"text-decoration: underline\">x direction cell length<\/span>, <span style=\"text-decoration: underline\">minimum grid size<\/span>, and <span style=\"text-decoration: underline\">cell length<\/span>. So I don&rsquo;t know what definition to choose in this case.<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\">My<strong> <span>&Delta;<\/span>x<\/strong>, <strong><span>&Delta;<\/span>y<\/strong>, and <strong><span>&Delta;<\/span>z<\/strong> mesh sizes around my blade (wall) are below,<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\"><strong>\u2206Y<\/strong><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span>1.66E-06m (<em>Y+ = 1<\/em>)<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\"><strong>\u2206X<\/strong><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span>1.99E-04m (<em>X+ = 120<\/em>)<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\"><strong>\u2206Z<\/strong><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <\/span>4.98E-05m (<em>Z+ = 30<\/em>)<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\">So, what value should i use for my time-step calculations ?<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\">Also, i have seen some people are using cube root method as well, can someone explain this method as well, and are there any other methods that ANSYS has recommended to calculate time-step ?<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\">&nbsp;<\/p>\n<p class=\"MsoNormal\" style=\"text-align: justify\">Highly appreciate for the guidance.<\/p>\n","protected":false},"template":"","class_list":["post-295681","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["255600","13659","199842"],"_bbp_author_ip":["23.206.193.154"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["1374"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["295681"],"_bbp_forum_id":["27792"],"_bbp_engagement":["13659","199842","255600"],"_bbp_voice_count":["3"],"_bbp_reply_count":["6"],"_bbp_last_reply_id":["296727"],"_bbp_last_active_id":["296727"],"_bbp_last_active_time":["2023-08-03 10:33:50"]},"test":"k1465822kingston-ac-uk"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/295681","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\/295681\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=295681"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}