{"id":373331,"date":"2024-07-24T00:57:37","date_gmt":"2024-07-24T00:57:37","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/?post_type=topic&#038;p=373331"},"modified":"2024-07-24T00:57:37","modified_gmt":"2024-07-24T00:57:37","slug":"doubt-on-gravity-effect-at-pipe-oulet-in-fluent","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/doubt-on-gravity-effect-at-pipe-oulet-in-fluent\/","title":{"rendered":"Doubt on gravity effect at pipe oulet in Fluent"},"content":{"rendered":"<p>Hi! I&#8217;m simulating some sort of y-elbow piping, as of now I have a prevalently hydrogen stream outflowing in ambient air.<br \/>The flow is going upwards, in the same direction of my&nbsp;<em>Y&nbsp;<\/em> axis. If I set gravity at -9.81<em>m\/s^2<\/em> (with force of gravity pushing down), I get this:<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/24-07-2024-1721781789-gravity-.png\" alt=\"\"><\/p>\n<p>The way the low density H2 flow is stopped and pushed back by the denser ambient air really leaves me puzzled, it really looks like the buoyancy effects are reversed here.<\/p>\n<p>I tried changing the sign of the gravity value, and I see something which embodies the expectation I originally had:<img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/24-07-2024-1721782114-gravityplus.png\" alt=\"\"><\/p>\n<p>The contour inside the pipe fades to red because the hydrogen stream is partly premixed with air.<br \/>And finally if I try to set it to 0 <em>m\/s^2<\/em>, I get the obvious confirmation that gravity is playing quite a role in the first contour I uploaded.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/24-07-2024-1721782041-gravity0.png\" alt=\"\"><\/p>\n<p>I&#8217;m using the ideal gas model with operating density set to 0.<\/p>\n<p>Am I beautifully mixing things up, or is there actually something strange going on?<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"template":"","class_list":["post-373331","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":["79.18.229.105"],"_bbp_subscription":["60427","199"],"_btv_view_count":["251"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["373331"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","60427"],"_bbp_voice_count":["2"],"_bbp_reply_count":["9"],"_bbp_last_reply_id":["374730"],"_bbp_last_active_id":["374730"],"_bbp_last_active_time":["2024-08-01 15:22:34"]},"test":"alex-chiellamail-polimi-it"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/373331","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\/373331\/revisions"}],"predecessor-version":[{"id":373332,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/373331\/revisions\/373332"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=373331"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}