{"id":461214,"date":"2026-07-11T13:20:35","date_gmt":"2026-07-11T13:20:35","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/residuals-spikes-even-when-physical-flow-field-is-correct\/"},"modified":"2026-07-11T13:20:35","modified_gmt":"2026-07-11T13:20:35","slug":"residuals-spikes-even-when-physical-flow-field-is-correct","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/residuals-spikes-even-when-physical-flow-field-is-correct\/","title":{"rendered":"Residuals spikes even when physical flow field is correct"},"content":{"rendered":"<p>&lt;p&gt;Hello there,&lt;br&gt;&lt;br&gt;I am simulating a 3D combustion problem and I noticed large residual spikes as shown in the image. I checked all possible reasons of that which I could find online such as mesh quality, check physical flow field, under relaxation factor, etc. My mesh reports min orthogonal quality ~0.17 which I believe is fine, the physical flow field is as expected (not perfectly stable but flame is establishing correctly), tried reducing under relaxation factors, but no change. Since, I kept it overnight so I actually don&#8217;t know exactly after what iteration these spikes started. But I was running another simulation with exact same setup but different mesh, observing that, I assume spikes started after 1500 iteration. One more important note is that, I previously ran few same setup simulation with different meshes but I never encountered spikes in that. Can you please suggest something on this?&lt;br&gt;&lt;br&gt;Method: Steady-state, pressure based, absolute, gravity on&lt;br&gt;Models: Standard k-epsilon, partially premixed combustion with FGM&lt;br&gt;Scheme: SIMPLE (tried with SIMPLEC also, but still same issue)&lt;br&gt;Fuel\/Ox: H2\/Air&lt;\/p&gt;&lt;p&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/07\/11-07-2026-1783775923-residuals.png\" alt=\"\" width=\"683\" height=\"442\" \/>&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-461214","topic","type-topic","status-publish","hentry","topic-tag-cfd-combustion","topic-tag-cfd-fluent","topic-tag-hydrogen-combustion","topic-tag-residuals"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["461214"],"_bbp_subscription":["540264","199"],"_bbp_author_ip":["14.139.128.12"],"_bbp_last_reply_id":["461248"],"_bbp_last_active_id":["461248"],"_bbp_last_active_time":["2026-07-13 08:46:12"],"_bbp_reply_count":["1"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["540264","199"],"_btv_view_count":["28"],"_bbp_topic_status":["unanswered"]},"test":"shezanghamatgmail-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/461214","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\/461214\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=461214"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}