{"id":402184,"date":"2024-12-30T12:17:55","date_gmt":"2024-12-30T12:17:55","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/"},"modified":"2024-12-30T12:17:55","modified_gmt":"2024-12-30T12:17:55","slug":"how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/","title":{"rendered":"How molecular weight is defined using incompressible ideal gas in species model?"},"content":{"rendered":"<p>&lt;p&gt;Hello everyone,&lt;\/p&gt;&lt;p&gt;I&#8217;m modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However,&nbsp; the &#8220;Mw&#8221;, molecular weight of mixture, is not explicitly defined for users. Anyone konws how the molecular weight is calculated by fluent using incompressible ideal gas law in species model? It&#8217;s not illustrated in user guide nor theory guide.&nbsp;&lt;\/p&gt;&lt;p&gt;Best regards.&lt;\/p&gt;&lt;p&gt;<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/12\/30-12-2024-1735560647-mceclip1.png\" width=\"970\" height=\"466\" \/>&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-402184","topic","type-topic","status-publish","hentry","topic-tag-fluent","topic-tag-gas-dispersion","topic-tag-incompressible-flow","topic-tag-species-diffusion"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Hello everyone,I&#039;m modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the &quot;Mw&quot;, molecular weight of mixture, is not explicitly defined for users.\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/\" \/>\n\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 4.9.10\" \/>\n\t\t<meta property=\"og:locale\" content=\"en_US\" \/>\n\t\t<meta property=\"og:site_name\" content=\"Ansys Learning Forum | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"How molecular weight is defined using incompressible ideal gas in species model? | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"Hello everyone,I&#039;m modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the &quot;Mw&quot;, molecular weight of mixture, is not explicitly defined for users.\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2024-12-30T12:17:55+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2024-12-30T12:17:55+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"How molecular weight is defined using incompressible ideal gas in species model? | Ansys Learning Forum\" \/>\n\t\t<meta name=\"twitter:description\" content=\"Hello everyone,I&#039;m modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the &quot;Mw&quot;, molecular weight of mixture, is not explicitly defined for users.\" \/>\n\t\t<script type=\"application\/ld+json\" class=\"aioseo-schema\">\n\t\t\t{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\\\/#breadcrumblist\",\"itemListElement\":[{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/#listItem\",\"name\":\"Topics\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/#listItem\",\"position\":2,\"name\":\"Topics\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic-tag\\\/fluent\\\/#listItem\",\"name\":\"fluent\"},\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"name\":\"Home\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic-tag\\\/fluent\\\/#listItem\",\"position\":3,\"name\":\"fluent\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic-tag\\\/fluent\\\/\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\\\/#listItem\",\"name\":\"How molecular weight is defined using incompressible ideal gas in species model?\"},\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/#listItem\",\"name\":\"Topics\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\\\/#listItem\",\"position\":4,\"name\":\"How molecular weight is defined using incompressible ideal gas in species model?\",\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic-tag\\\/fluent\\\/#listItem\",\"name\":\"fluent\"}}]},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#organization\",\"name\":\"Ansys Learning Forum\",\"description\":\"Ansys Innovation Space\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\\\/#webpage\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\\\/\",\"name\":\"How molecular weight is defined using incompressible ideal gas in species model? | Ansys Learning Forum\",\"description\":\"Hello everyone,I'm modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the \\\"Mw\\\", molecular weight of mixture, is not explicitly defined for users.\",\"inLanguage\":\"en-US\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#website\"},\"breadcrumb\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\\\/#breadcrumblist\"},\"datePublished\":\"2024-12-30T12:17:55+00:00\",\"dateModified\":\"2024-12-30T12:17:55+00:00\"},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#website\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/\",\"name\":\"Ansys Learning Forum\",\"description\":\"Ansys Innovation Space\",\"inLanguage\":\"en-US\",\"publisher\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#organization\"}}]}\n\t\t<\/script>\n\t\t<!-- All in One SEO -->\n\n","aioseo_head_json":{"title":"How molecular weight is defined using incompressible ideal gas in species model? | Ansys Learning Forum","description":"Hello everyone,I'm modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the \"Mw\", molecular weight of mixture, is not explicitly defined for users.","canonical_url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"BreadcrumbList","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/#breadcrumblist","itemListElement":[{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum#listItem","position":1,"name":"Home","item":"https:\/\/innovationspace.ansys.com\/forum","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/topics\/#listItem","name":"Topics"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/topics\/#listItem","position":2,"name":"Topics","item":"https:\/\/innovationspace.ansys.com\/forum\/topics\/","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic-tag\/fluent\/#listItem","name":"fluent"},"previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum#listItem","name":"Home"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic-tag\/fluent\/#listItem","position":3,"name":"fluent","item":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic-tag\/fluent\/","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/#listItem","name":"How molecular weight is defined using incompressible ideal gas in species model?"},"previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/topics\/#listItem","name":"Topics"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/#listItem","position":4,"name":"How molecular weight is defined using incompressible ideal gas in species model?","previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic-tag\/fluent\/#listItem","name":"fluent"}}]},{"@type":"Organization","@id":"https:\/\/innovationspace.ansys.com\/forum\/#organization","name":"Ansys Learning Forum","description":"Ansys Innovation Space","url":"https:\/\/innovationspace.ansys.com\/forum\/"},{"@type":"WebPage","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/#webpage","url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/","name":"How molecular weight is defined using incompressible ideal gas in species model? | Ansys Learning Forum","description":"Hello everyone,I'm modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the \"Mw\", molecular weight of mixture, is not explicitly defined for users.","inLanguage":"en-US","isPartOf":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/#website"},"breadcrumb":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/#breadcrumblist"},"datePublished":"2024-12-30T12:17:55+00:00","dateModified":"2024-12-30T12:17:55+00:00"},{"@type":"WebSite","@id":"https:\/\/innovationspace.ansys.com\/forum\/#website","url":"https:\/\/innovationspace.ansys.com\/forum\/","name":"Ansys Learning Forum","description":"Ansys Innovation Space","inLanguage":"en-US","publisher":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/#organization"}}]},"og:locale":"en_US","og:site_name":"Ansys Learning Forum | Ansys Innovation Space","og:type":"article","og:title":"How molecular weight is defined using incompressible ideal gas in species model? | Ansys Learning Forum","og:description":"Hello everyone,I'm modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the &quot;Mw&quot;, molecular weight of mixture, is not explicitly defined for users.","og:url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/","article:published_time":"2024-12-30T12:17:55+00:00","article:modified_time":"2024-12-30T12:17:55+00:00","twitter:card":"summary_large_image","twitter:title":"How molecular weight is defined using incompressible ideal gas in species model? | Ansys Learning Forum","twitter:description":"Hello everyone,I'm modeling dispersion of CO in the air. The species model without chemical reaction is used. I have specified the density of mixture material as incompressible ideal gas. The incompressible ideal gas is defined as followed as reference in user guide. However, the &quot;Mw&quot;, molecular weight of mixture, is not explicitly defined for users."},"aioseo_meta_data":{"post_id":"402184","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":"2025-10-19 10:47:19","updated":"2026-09-17 15:04:10","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\/forum\" 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\/forum\/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\/forum\/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\tHow molecular weight is defined using incompressible ideal gas in species model?\n\t\t<\/span><\/div>","aioseo_breadcrumb_json":[{"label":"Home","link":"https:\/\/innovationspace.ansys.com\/forum"},{"label":"Topics","link":"https:\/\/innovationspace.ansys.com\/forum\/topics\/"},{"label":"fluent","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic-tag\/fluent\/"},{"label":"How molecular weight is defined using incompressible ideal gas in species model?","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-molecular-weight-is-defined-using-incompressible-ideal-gas-in-species-model\/"}],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["402184"],"_bbp_subscription":["51510","23673"],"_bbp_author_ip":["58.249.112.28"],"_bbp_last_reply_id":["403096"],"_bbp_last_active_id":["403096"],"_bbp_last_active_time":["2024-12-31 17:51:53"],"_bbp_reply_count":["1"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["51510","23673"],"_btv_view_count":["651"],"_bbp_topic_status":["unanswered"]},"test":"bfdef4e41fe840e99014e0c0ef18055b3cd7380f"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/402184","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\/402184\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=402184"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}