{"id":372418,"date":"2024-07-17T14:48:48","date_gmt":"2024-07-17T14:48:48","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/strange-divergence-in-natural-circulation-simulation-simulation-using-vof\/"},"modified":"2024-07-17T14:48:48","modified_gmt":"2024-07-17T14:48:48","slug":"strange-divergence-in-natural-circulation-simulation-simulation-using-vof","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/strange-divergence-in-natural-circulation-simulation-simulation-using-vof\/","title":{"rendered":"Strange Divergence in natural circulation simulation simulation using VOF"},"content":{"rendered":"<p>Hi everyone,&nbsp;<\/p>\n<p>I&#8217;m a freshman doing transient simulation. I&#8217;m doing 2D tranient natural circulation simulation using VOF model. In the case, Water will be heated and generated vapor to drive the circulation. Model is shown below.&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721226563-mceclip2.png\" width=\"397\" height=\"167\"><\/p>\n<p>&nbsp;<\/p>\n<p>Firstly, solution converge and contour seemed reasonable. However, solution suddenly diverged with global courant number surged to 9322.7.&nbsp;&nbsp;<\/p>\n<p>Discretization scheme and&nbsp; residual and console is shown below.&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721226730-mceclip3.png\" width=\"268\" height=\"503\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721225978-mceclip0.png\" width=\"518\" height=\"481\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721226012-mceclip1.png\" width=\"515\" height=\"388\"><\/p>\n<p>messages shown indicates that velocity field is abnormal and it did. Below velocity, volume fraction of vapor and&nbsp; at last time step.&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721226956-mceclip5.png\" width=\"391\" height=\"212\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721227287-mceclip6.png\" width=\"379\" height=\"198\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721227354-mceclip7.png\" width=\"404\" height=\"216\"><\/p>\n<p>I really have no idea that I have encountered the siuation when I run it again.&nbsp;<\/p>\n<p>I&#8217;m using Lee model and parameters used in the model is by default. Fixed e-4 time step is set.&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/17-07-2024-1721226808-mceclip4.png\" width=\"672\" height=\"399\"><\/p>\n<p>I&#8217;m really confused by the sudden ascending courant number and abrupt divergence. Any kind of suggestions would do me a great help<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"template":"","class_list":["post-372418","topic","type-topic","status-closed","hentry","topic-tag-c-vof","topic-tag-courant-number","topic-tag-fluent","topic-tag-transient"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["51510","199"],"_bbp_author_ip":["2001:250:3002:3270:7f84:d980:f12:d1e5"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_bbp_likes_count":["1"],"_btv_view_count":["207"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["372418"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","51510"],"_bbp_voice_count":["2"],"_bbp_reply_count":["6"],"_bbp_last_reply_id":["373002"],"_bbp_last_active_id":["373002"],"_bbp_last_active_time":["2024-07-22 12:20:09"]},"test":"bfdef4e41fe840e99014e0c0ef18055b3cd7380f"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/372418","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\/372418\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=372418"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}