{"id":459719,"date":"2026-06-14T14:46:55","date_gmt":"2026-06-14T14:46:55","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/inconsistency-ls-prepost-and-manual-for-icfd_boundary_prescribed_sptransp_conc\/"},"modified":"2026-06-14T14:46:55","modified_gmt":"2026-06-14T14:46:55","slug":"inconsistency-ls-prepost-and-manual-for-icfd_boundary_prescribed_sptransp_conc","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/inconsistency-ls-prepost-and-manual-for-icfd_boundary_prescribed_sptransp_conc\/","title":{"rendered":"Inconsistency LS-PrePost and manual for ICFD_BOUNDARY_PRESCRIBED_SPTRANSP_CONC"},"content":{"rendered":"<p>&lt;p&gt;Hello everyone,&lt;\/p&gt;&lt;p&gt;I encountered a possible inconsistency when setting the concentration boundary condition for species transport in LS-DYNA.&lt;\/p&gt;&lt;p&gt;The keyword&nbsp;<strong><code>*ICFD_BOUNDARY_PRESCRIBED_&lt;wbr&gt;SPTRANSP_CONC<\/code><\/strong>&nbsp;appears differently in the&nbsp;<strong>LS-PrePost keyword interface<\/strong>&nbsp;and in the&nbsp;<strong>LS-DYNA manual<\/strong>.&lt;\/p&gt;&lt;p&gt;In&nbsp;<strong>LS-PrePost<\/strong>, the keyword is shown as a&nbsp;<strong>two-line structure<\/strong>:&lt;\/p&gt;<\/p>\n<ul>\n<li>&lt;p&gt;the first line defines the&nbsp;<strong>PID<\/strong>&lt;\/p&gt;<\/li>\n<li>&lt;p&gt;the second line contains the&nbsp;<strong>LCID values<\/strong>&lt;\/p&gt;<\/li>\n<\/ul>\n<p>&lt;p&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/06\/14-06-2026-1781448179-1.png\" alt=\"\" \/>&lt;\/p&gt;&lt;p&gt;However, in the&nbsp;<strong>LS-DYNA manual<\/strong>, the keyword is documented in a&nbsp;<strong>single-line format<\/strong>&nbsp;where&nbsp;<strong>PID, LCID and CONC fields<\/strong>&nbsp;appear together.&lt;\/p&gt;&lt;p&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/06\/14-06-2026-1781448285-2.png\" alt=\"\" \/>&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;Because of this difference, I observed the following behaviour:&lt;\/p&gt;<\/p>\n<ol>\n<li>&lt;p&gt;If I follow the format shown in&nbsp;<strong>LS-PrePost<\/strong>, the solver produces an error:&lt;\/p&gt;<\/li>\n<\/ol>\n<p>&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&nbsp;&lt;\/div&gt;&lt;div&gt;&lt;div&gt;&lt;div id=&#8221;m_2277478720517859887gmail-code-block-viewer&#8221; dir=&#8221;ltr&#8221;&gt;&lt;div&gt;&lt;div&gt;input conversion error&lt;br&gt;forrtl: severe (64)&nbsp;&lt;\/div&gt;&lt;div&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/06\/14-06-2026-1781448302-3.png\" alt=\"\" \/>&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;div&gt;&lt;div&gt;&nbsp;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;p&gt;and the simulation cannot start.&lt;\/p&gt;&lt;p&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/06\/14-06-2026-1781448395-5.png\" alt=\"\" \/>&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;<\/p>\n<ol start=\"2\">\n<li>&lt;p&gt;<strong>Even<\/strong>&nbsp;if I instead follow the&nbsp;<strong>manual format<\/strong>&nbsp;and remove the second line, the simulation runs but the&nbsp;<strong>concentration boundary condition does not seem to be applied<\/strong>. In this case:&lt;\/p&gt;<\/li>\n<\/ol>\n<ul>\n<li>&lt;p&gt;the inlet concentration remains&nbsp;<strong>zero<\/strong>&lt;\/p&gt;<\/li>\n<li>&lt;p&gt;residuals for the scalar transport equation are&nbsp;<strong>not computed&lt;br&gt;<\/strong>&lt;\/p&gt;&lt;p&gt;<strong><img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2026\/06\/14-06-2026-1781448349-4.png\" alt=\"\" \/>&lt;br&gt;<\/strong>&lt;\/p&gt;<\/li>\n<\/ul>\n<p>&lt;p&gt;I also noticed a similar mismatch for another keyword related to species transport:&lt;\/p&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&lt;div&gt;&nbsp;&lt;\/div&gt;&lt;div&gt;&lt;div&gt;&lt;div id=&#8221;m_2277478720517859887gmail-code-block-viewer&#8221; dir=&#8221;ltr&#8221;&gt;&lt;div&gt;&lt;div&gt;*ICFD_MODEL_SPECIES_TRANSPORT&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;div&gt;&lt;div&gt;&nbsp;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;\/div&gt;&lt;p&gt;where the format in the&nbsp;<strong>LS-PrePost interface<\/strong>&nbsp;does not fully match the&nbsp;<strong>manual description<\/strong>.&lt;\/p&gt;&lt;p&gt;Because of this inconsistency I am currently unable to run simulations that require&nbsp;<strong>inlet concentration boundary conditions for species transport<\/strong>.&lt;\/p&gt;&lt;p&gt;Could anyone clarify:&lt;\/p&gt;<\/p>\n<ul>\n<li>&lt;p&gt;<strong>The correct keyword format&nbsp;&nbsp;<code>*ICFD_BOUNDARY_&lt;wbr&gt;PRESCRIBED_SPTRANSP_CONC<\/code><\/strong>&lt;\/p&gt;<\/li>\n<li>&lt;p&gt;whether this difference between LS-PrePost and the manual is expected&lt;\/p&gt;<\/li>\n<li>&lt;p&gt;or if this might be a bug?&lt;\/p&gt;<\/li>\n<\/ul>\n<p>&lt;div&gt;My LS-DYNA version: R16 SMP and LS-PrePost version: 4.12.6&lt;\/div&gt;&lt;p&gt;Thank you so so so much for any guidance!&nbsp;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-459719","topic","type-topic","status-publish","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27814"],"_bbp_topic_id":["459719"],"_bbp_subscription":["658864","58821","480261"],"_bbp_author_ip":["86.12.29.194"],"_bbp_last_reply_id":["460092"],"_bbp_last_active_id":["460092"],"_bbp_last_active_time":["2026-06-19 13:05:00"],"_bbp_reply_count":["10"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["3"],"_bbp_engagement":["658864","58821","480261"],"_btv_view_count":["182"],"_bbp_topic_status":["unanswered"],"_bbp_notification_enabled":["658864"],"_bbp_likes_count":["1"]},"test":"k23052087kcl-ac-uk"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/459719","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\/459719\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=459719"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}