{"id":450971,"date":"2026-01-22T02:06:23","date_gmt":"2026-01-22T02:06:23","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/difficulty-in-complex-source-term-linearization\/"},"modified":"2026-01-22T02:06:23","modified_gmt":"2026-01-22T02:06:23","slug":"difficulty-in-complex-source-term-linearization","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/difficulty-in-complex-source-term-linearization\/","title":{"rendered":"Difficulty in Complex Source Term Linearization"},"content":{"rendered":"<p>&lt;p&gt;Hello everyone\uff01&lt;\/p&gt;&lt;p&gt;&nbsp;I used <strong>DEFINE_SOURCE<\/strong> to define mass, momentum, and energy source terms. I am now encountering <strong>convergence difficulties<\/strong>. After investigation, it seems the issue may be that I did not linearize the source terms. In the calculation, I specified them as explicit: <strong>dS[eqn] = 0<\/strong>. I am now planning to address the problem through <strong>source term linearization<\/strong>, but my <strong>source terms are very complex<\/strong>, making it difficult to derive the derivatives of the source terms with respect to the solution variables. In this case, <strong>how should I specify dS[eqn]?<\/strong> Additionally, I have observed that even with dS[eqn] = 0, convergence can be achieved for <strong>positive source terms<\/strong>, but it fails for <strong>negative source terms<\/strong>.&lt;\/p&gt;&lt;p&gt;Thank you very much for your time and assistance!&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-450971","topic","type-topic","status-publish","hentry","topic-tag-define-source","topic-tag-numerical-instability-2","topic-tag-udf"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["291848"],"_bbp_topic_id":["450971"],"_bbp_subscription":["526202","23673"],"_bbp_author_ip":["45.39.199.149"],"_bbp_last_reply_id":["451111"],"_bbp_last_active_id":["451111"],"_bbp_last_active_time":["2026-01-23 03:27:19"],"_bbp_reply_count":["2"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["526202","23673"],"_btv_view_count":["239"],"_bbp_topic_status":["unanswered"]},"test":"james411projectgmail-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/450971","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\/450971\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=450971"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}