{"id":171264,"date":"2023-06-05T07:06:01","date_gmt":"2023-06-05T07:06:01","guid":{"rendered":"\/knowledge\/forums\/topic\/i-have-hooked-the-surface-reaction-udf-define_sr_rate-to-a-surface-reaction-in-fluent-when-i-run-fluent-the-rate-for-that-surface-reaction-is-always-zero-no-matter-what-is-specified-in-the-udf-the\/"},"modified":"2023-07-31T12:30:13","modified_gmt":"2023-07-31T12:30:13","slug":"i-have-hooked-the-surface-reaction-udf-define_sr_rate-to-a-surface-reaction-in-fluent-when-i-run-fluent-the-rate-for-that-surface-reaction-is-always-zero-no-matter-what-is-specified-in-the-udf-the","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/i-have-hooked-the-surface-reaction-udf-define_sr_rate-to-a-surface-reaction-in-fluent-when-i-run-fluent-the-rate-for-that-surface-reaction-is-always-zero-no-matter-what-is-specified-in-the-udf-the\/","title":{"rendered":"I have hooked the surface reaction UDF DEFINE_SR_RATE to a surface reaction in Fluent. When I run Fluent, the rate for that surface reaction is always zero, no matter what is specified in the UDF. The UDF is properly hooked. What could be wrong?  Also, if both Arrehnius coefficients ( via GUI) and DEFINE_SR_RATE are specified for a surface reaction, which will take precedence?"},"content":{"rendered":"<p>The reaction is likely missing from the reaction mechanism. Surface reactions must be included in the reaction mechanism by editing the mechanism in the Mixture Template.  There, make sure that the Reaction Type is set to &#8220;All&#8221;  so that the surface reaction can be included in the mechanism. UDFs that are hooked and apply to a given surface reaction will take precedence over any coefficients that are defined in the GUI.<\/p>\n","protected":false},"template":"","class_list":["post-171264","topic","type-topic","status-publish","hentry","topic-tag-17-2","topic-tag-fluent","topic-tag-fluid-dynamics","topic-tag-species-reactions","topic-tag-surface-chemistry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"The reaction is likely missing from the reaction mechanism. Surface reactions must be included in the reaction mechanism by editing the mechanism in the Mixture Template. There, make sure that the Reaction Type is set to &quot;All&quot; so that the surface reaction can be included in the mechanism. 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Also, if both Arrehnius coefficients ( via GUI) and DEFINE_SR_RATE are specified for a surface reaction, which will take precedence? | Ansys Knowledge\" \/>\n\t\t<meta property=\"og:description\" content=\"The reaction is likely missing from the reaction mechanism. Surface reactions must be included in the reaction mechanism by editing the mechanism in the Mixture Template. There, make sure that the Reaction Type is set to &quot;All&quot; so that the surface reaction can be included in the mechanism. UDFs that are hooked and apply to\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/i-have-hooked-the-surface-reaction-udf-define_sr_rate-to-a-surface-reaction-in-fluent-when-i-run-fluent-the-rate-for-that-surface-reaction-is-always-zero-no-matter-what-is-specified-in-the-udf-the\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2023-06-05T07:06:01+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2023-07-31T12:30:13+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"I have hooked the surface reaction UDF DEFINE_SR_RATE to a surface reaction in Fluent. When I run Fluent, the rate for that surface reaction is always zero, no matter what is specified in the UDF. The UDF is properly hooked. What could be wrong? Also, if both Arrehnius coefficients ( via GUI) and DEFINE_SR_RATE are specified for a surface reaction, which will take precedence? | Ansys Knowledge\" \/>\n\t\t<meta name=\"twitter:description\" content=\"The reaction is likely missing from the reaction mechanism. Surface reactions must be included in the reaction mechanism by editing the mechanism in the Mixture Template. There, make sure that the Reaction Type is set to &quot;All&quot; so that the surface reaction can be included in the mechanism. 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Also, if both Arrehnius coefficients ( via GUI) and DEFINE_SR_RATE are specified for a surface reaction, which will take precedence?","previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluent\/#listItem","name":"fluent"}}]},{"@type":"Organization","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/#organization","name":"Ansys Knowledge","description":"Ansys Innovation Space","url":"https:\/\/innovationspace.ansys.com\/knowledge\/"},{"@type":"WebPage","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/i-have-hooked-the-surface-reaction-udf-define_sr_rate-to-a-surface-reaction-in-fluent-when-i-run-fluent-the-rate-for-that-surface-reaction-is-always-zero-no-matter-what-is-specified-in-the-udf-the\/#webpage","url":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/i-have-hooked-the-surface-reaction-udf-define_sr_rate-to-a-surface-reaction-in-fluent-when-i-run-fluent-the-rate-for-that-surface-reaction-is-always-zero-no-matter-what-is-specified-in-the-udf-the\/","name":"I have hooked the surface reaction UDF DEFINE_SR_RATE to a surface reaction in Fluent. 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UDFs that are hooked and apply to"},"aioseo_meta_data":{"post_id":"171264","title":null,"description":null,"keywords":null,"keyphrases":null,"primary_term":null,"canonical_url":null,"og_title":null,"og_description":null,"og_object_type":"default","og_image_type":"default","og_image_url":null,"og_image_width":null,"og_image_height":null,"og_image_custom_url":null,"og_image_custom_fields":null,"og_video":null,"og_custom_url":null,"og_article_section":null,"og_article_tags":null,"twitter_use_og":false,"twitter_card":"default","twitter_image_type":"default","twitter_image_url":null,"twitter_image_custom_url":null,"twitter_image_custom_fields":null,"twitter_title":null,"twitter_description":null,"schema":{"blockGraphs":[],"customGraphs":[],"default":{"data":{"Article":[],"Course":[],"Dataset":[],"FAQPage":[],"Movie":[],"Person":[],"Product":[],"ProductReview":[],"Car":[],"Recipe":[],"Service":[],"SoftwareApplication":[],"WebPage":[]},"graphName":"","isEnabled":true},"graphs":[]},"schema_type":"default","schema_type_options":null,"pillar_content":false,"robots_default":true,"robots_noindex":false,"robots_noarchive":false,"robots_nosnippet":false,"robots_nofollow":false,"robots_noimageindex":false,"robots_noodp":false,"robots_notranslate":false,"robots_max_snippet":null,"robots_max_videopreview":null,"robots_max_imagepreview":"large","priority":null,"frequency":null,"local_seo":null,"limit_modified_date":false,"created":"2025-10-18 01:47:12","updated":"2026-07-30 05:36:18","ai":null,"breadcrumb_settings":null,"seo_analyzer_scan_date":null},"aioseo_breadcrumb":"<div class=\"aioseo-breadcrumbs\"><span class=\"aioseo-breadcrumb\">\n\t\t\t<a href=\"https:\/\/innovationspace.ansys.com\/knowledge\" title=\"Home\">Home<\/a>\n\t\t<\/span><span class=\"aioseo-breadcrumb-separator\">&raquo;<\/span><span class=\"aioseo-breadcrumb\">\n\t\t\t<a href=\"https:\/\/innovationspace.ansys.com\/knowledge\/topics\/\" title=\"Topics\">Topics<\/a>\n\t\t<\/span><span class=\"aioseo-breadcrumb-separator\">&raquo;<\/span><span class=\"aioseo-breadcrumb\">\n\t\t\t<a href=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluent\/\" title=\"fluent\">fluent<\/a>\n\t\t<\/span><span class=\"aioseo-breadcrumb-separator\">&raquo;<\/span><span class=\"aioseo-breadcrumb\">\n\t\t\tI have hooked the surface reaction UDF DEFINE_SR_RATE to a surface reaction in Fluent. When I run Fluent, the rate for that surface reaction is always zero, no matter what is specified in the UDF. The UDF is properly hooked. What could be wrong?  Also, if both Arrehnius coefficients ( via GUI) and DEFINE_SR_RATE are specified for a surface reaction, which will take precedence?\n\t\t<\/span><\/div>","aioseo_breadcrumb_json":[{"label":"Home","link":"https:\/\/innovationspace.ansys.com\/knowledge"},{"label":"Topics","link":"https:\/\/innovationspace.ansys.com\/knowledge\/topics\/"},{"label":"fluent","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluent\/"},{"label":"I have hooked the surface reaction UDF DEFINE_SR_RATE to a surface reaction in Fluent. When I run Fluent, the rate for that surface reaction is always zero, no matter what is specified in the UDF. The UDF is properly hooked. What could be wrong?  Also, if both Arrehnius coefficients ( via GUI) and DEFINE_SR_RATE are specified for a surface reaction, which will take precedence?","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/i-have-hooked-the-surface-reaction-udf-define_sr_rate-to-a-surface-reaction-in-fluent-when-i-run-fluent-the-rate-for-that-surface-reaction-is-always-zero-no-matter-what-is-specified-in-the-udf-the\/"}],"acf":[],"custom_fields":[{"0":{"_wp_page_template":["default"],"_bbp_last_active_time":["2\/6\/2023 20:20"],"_bbp_forum_id":["27784"],"_bbp_author_ip":["209.182.204.162"],"_btv_view_count":["1216"],"siebel_km_number":["2048548"],"product_version":["17.2"],"km_published_date":["2017-03-01T00:00:00.000Z"],"family":["Fluid Dynamics"],"application_name":["FLUENT"]},"test":"articlesansys-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/171264","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/171264\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/media?parent=171264"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}