{"id":403326,"date":"2025-01-02T23:15:15","date_gmt":"2025-01-02T23:15:15","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/mixture-binary-diffusion-cofficent-inf-value\/"},"modified":"2025-01-02T23:16:20","modified_gmt":"2025-01-02T23:16:20","slug":"mixture-binary-diffusion-cofficent-inf-value","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/mixture-binary-diffusion-cofficent-inf-value\/","title":{"rendered":"Mixture Binary Diffusion Coefficient(INF Value)"},"content":{"rendered":"<p>&lt;p&gt;&lt;p&gt;Hello,&nbsp;&lt;\/p&gt;&lt;p&gt;I need help determining why my opposed flow simulations are not producing real mixture binary diffusion coefficients. I am receiving the INF mixture binary diffusion coefficient across the whole domain in the Ansys output file.&lt;\/p&gt;&lt;p&gt;Initially, I ran opposed flow flame (OFB) simulations with formaldehyde and air in inlets one and two, respectively. The velocity of the gas flows is relatively low, which should allow for diffusion of the species across a significant portion of the control volume. I initially used a mixture averaged diffusion coefficient approach, and I received infinite diffusion coefficients for all my gasses but still produced a solution. I then switched to a multi-component mixture and still had the same issue. I increased my max grid points to 1000 across 0.43 CM domain length. I still did not get real values for the diffusion coefficients. I then went to the Ansys-provided OFB simulation example with hydrogen and air. I repeated the same process and still received &#8220;INF&#8221; diffusion coefficients.&nbsp;&lt;\/p&gt;&lt;p&gt;From the theory manual, the binary diffusion coefficients is written as follows:&nbsp;&lt;\/p&gt;&lt;p&gt;<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2025\/01\/02-01-2025-1735859459-mceclip0.png\" \/>&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;I checked the Transport file, and it appears to have the reduced collision diameter defined, but I am unsure how to check if it is appropriately calculating the (1,1) collision integral.&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;Has anyone come across this issue before? If so, do you know what the problem is? If not, do you know what could be causing Chemkin to output INF diffusion coefficients?&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-403326","topic","type-topic","status-publish","hentry","topic-tag-ansys-chemkin","topic-tag-chemkin","topic-tag-species-transport"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["403326"],"_bbp_subscription":["348362","23673"],"_bbp_author_ip":["208.127.66.230"],"_bbp_last_reply_id":["404770"],"_bbp_last_active_id":["404770"],"_bbp_last_active_time":["2025-01-13 23:08:31"],"_bbp_reply_count":["7"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["348362","23673"],"_btv_view_count":["475"],"_bbp_topic_status":["unanswered"],"_edit_last":["348362"],"_bbp_revision_log":["a:1:{i:403327;a:2:{s:6:\"author\";i:348362;s:6:\"reason\";s:20:\"coefficient spelling\";}}"],"_bbp_likes_count":["1"],"_bbp_notification_enabled":["348362"]},"test":"djr6248psu-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/403326","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":1,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/403326\/revisions"}],"predecessor-version":[{"id":403327,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/403326\/revisions\/403327"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=403326"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}