{"id":360839,"date":"2024-04-06T11:13:07","date_gmt":"2024-04-06T11:13:07","guid":{"rendered":"\/forum\/forums\/topic\/trouble-with-population-balance-for-bubble-column-simulation\/"},"modified":"2024-04-06T11:13:07","modified_gmt":"2024-04-06T11:13:07","slug":"trouble-with-population-balance-for-bubble-column-simulation","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/trouble-with-population-balance-for-bubble-column-simulation\/","title":{"rendered":"Trouble with population balance for bubble column simulation"},"content":{"rendered":"<p>Hello!<\/p>\n<p>I am trying to simulate a bubble column in Fluent with the following geometry.&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/04\/06-04-2024-1712400152-mceclip0.png\" width=\"732\" height=\"445\"><\/p>\n<p>However, I run into problems when I try to use the QMOM to account for the bubbles&#8217; polydispersity, coalescence, and breakage phenomena. The problematic result I am getting can be seen in the following figure:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/04\/06-04-2024-1712400199-mceclip1.png\"><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/04\/06-04-2024-1712400202-mceclip2.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/04\/06-04-2024-1712400413-mceclip4.png\" width=\"412\" height=\"210\"><\/p>\n<p>What is problematic is the larger bubbles. They just keep slowly increasing during the simulation and don&#8217;t stop. And to my understanding, it doesn&#8217;t make sense for larger bubbles to be located in these areas. That is, between the bubble plumes at the inlet and in the recirculating liquid flows.<\/p>\n<p>I have tried several things to try and fix this, such as:<\/p>\n<ul>\n<li>Different types of grids\n<ul>\n<li>Poly-hexcore (Fluent meshing)<\/li>\n<li>Polyhedral (Fluent meshing)<\/li>\n<li>Hexahedral (ICEM blocking)<\/li>\n<\/ul>\n<\/li>\n<li>Refining the meshes\n<ul>\n<li>I have tried having from 20 000 to 130 000 cells in the mesh<\/li>\n<\/ul>\n<\/li>\n<li>Adjusting the timestep\n<ul>\n<li>Fixed timestep between 1e-5 and 0.005 [s]<\/li>\n<\/ul>\n<\/li>\n<li>Playing with Under relaxation factors<\/li>\n<li>Tried 4 and 6 moments<\/li>\n<li>Tried different spatial discretization schemes\n<ul>\n<li>All schemes QUICK<\/li>\n<li>All schemes are QUICK, except moments, which is 1st order upwind<\/li>\n<li>All schemes are QUICK, except moments and turbulence, which is 1st order upwind<\/li>\n<\/ul>\n<\/li>\n<li>Tried the different time schemes\n<ul>\n<li>1st order, 2nd order, 2nd order bounded<\/li>\n<\/ul>\n<\/li>\n<li>Tried enabling warped-face gradient correction and higher-order term relaxation.<\/li>\n<\/ul>\n<p>I&#8217;m honestly out of ideas on what might be wrong. Any help would be very appreciated!<\/p>\n<p>&nbsp;<\/p>\n<p>Some extra info:<\/p>\n<p>The poly-hex-core and polyhedral meshes are just standard meshes made with fluent meshing and using the improve orthogonality and skewness option. A mesh made by using&nbsp; blocking in ICEM can be seen below:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/04\/06-04-2024-1712401287-mceclip5.png\"><\/p>\n<p>I have used the following for boundary conditions:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/04\/06-04-2024-1712401962-mceclip6.png\"><\/p>\n","protected":false},"template":"","class_list":["post-360839","topic","type-topic","status-closed","hentry","topic-tag-fluent-cfd-ansys-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["343047","199"],"_bbp_author_ip":["23.52.43.88"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["470"],"_bbp_topic_status":["unanswered"],"_bbp_likes_count":["1"],"_bbp_topic_id":["360839"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","343047"],"_bbp_voice_count":["2"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["362514"],"_bbp_last_active_id":["362514"],"_bbp_last_active_time":["2024-04-16 15:14:09"]},"test":"trygvelsstud-ntnu-no"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/360839","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\/360839\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=360839"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}