{"id":429082,"date":"2025-04-16T05:23:40","date_gmt":"2025-04-16T05:23:40","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/local-vs-global-cfl\/"},"modified":"2025-04-16T05:23:40","modified_gmt":"2025-04-16T05:23:40","slug":"local-vs-global-cfl","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/local-vs-global-cfl\/","title":{"rendered":"Local vs Global CFL"},"content":{"rendered":"<p>&lt;p&gt;Dear all,&nbsp;&lt;\/p&gt;&lt;p&gt;I am running a transient simulation of a partially-filled rotating cylinder with a explicit VOF formulation. Therefore I a monitoring both the global CFL and the maximum local CFL. My global CFL is around 0.15 but my maximum local CFL is around 0.5. I wanted to ask you if I can increase my maximum local CFL, as long as I keep my global CFL below 0.5 (to keep a stable simulation). Moreover, I also trying to imlpement surface tension effect. However, when I introduce surface tension between the water and the air, I have a large numerical diffusion at the interface when I start rotating. This numerical diffusion at the interface only starts when I start rotating the cylinder, and seems to be independent of the timestep that I take. I am using a constant value for the surface of&nbsp; 0.072N\/m, CSF model, Wall adhesion.&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-429082","topic","type-topic","status-publish","hentry","topic-tag-cfl-time-step-1","topic-tag-fluent","topic-tag-surface-tension","topic-tag-timestep-size-1"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["429082"],"_bbp_subscription":["505095","199"],"_bbp_author_ip":["152.88.0.137"],"_bbp_last_reply_id":["429125"],"_bbp_last_active_id":["429125"],"_bbp_last_active_time":["2025-04-16 10:40:53"],"_bbp_reply_count":["3"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["505095","199"],"_btv_view_count":["122"],"_bbp_topic_status":["unanswered"]},"test":"jose-simongremingerempa-ch"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/429082","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\/429082\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=429082"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}