{"id":453648,"date":"2026-03-03T12:35:34","date_gmt":"2026-03-03T12:35:34","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/periodic-bc-length-problem\/"},"modified":"2026-03-03T12:35:34","modified_gmt":"2026-03-03T12:35:34","slug":"periodic-bc-length-problem","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/periodic-bc-length-problem\/","title":{"rendered":"Periodic BC length problem"},"content":{"rendered":"<p>&lt;p&gt;Hi&lt;\/p&gt;&lt;p&gt;I am using a periodic bc along the length of a 3D pipe which is semi-circular cross-section. I have no slip BC at all walls and a slip BC at the top surface. I saw that the results are vastly dependent upon the periodic length taken along the streamwise direction. If i take a bigger length the results are coming much better than if i take only one-cell or a very short length along the streamwise direction. Why is this? The results should be independent upon the streamwise length? Can someone please clarify, thanks. I am using 2nd order for mom, pressure and first order for Reynolds stresses, coupled and least square cell based.&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-453648","topic","type-topic","status-publish","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["453648"],"_bbp_subscription":["296506","199"],"_bbp_author_ip":["129.11.145.115"],"_bbp_last_reply_id":["454585"],"_bbp_last_active_id":["454585"],"_bbp_last_active_time":["2026-03-16 10:04:16"],"_bbp_reply_count":["12"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["296506","199"],"_btv_view_count":["43"],"_bbp_topic_status":["unanswered"]},"test":"scaboleeds-ac-uk"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/453648","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\/453648\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=453648"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}