{"id":461409,"date":"2026-07-16T10:27:28","date_gmt":"2026-07-16T10:27:28","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/"},"modified":"2026-07-16T10:27:28","modified_gmt":"2026-07-16T10:27:28","slug":"simulating-semi-batch-process-change-velocity","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/","title":{"rendered":"Simulating Semi-Batch Process (Change Velocity)"},"content":{"rendered":"<p>&lt;p&gt;Hello,&lt;\/p&gt;&lt;p&gt;I am currently modelling a semi-batch precipitation process in an agitated vessel, where I have multiphase VOF (free surface tracking and volume tracking), SST k-w CC turbulence model, species transport (mass balance) and user defined scalars (population balance) with UDFs for source terms and I want to introduce a change by closing feed inlet boundary condition. I have a velocity-inlet (0.00877 m\/s) for feed pipe face and pressure-outlet for top.&lt;\/p&gt;&lt;p&gt;As I understand there are two ways to do this:&lt;\/p&gt;<\/p>\n<ol>\n<li>Change velocity-inlet to wall<\/li>\n<li>Set velocity-inlet to 0 m\/s<\/li>\n<\/ol>\n<p>&lt;p&gt;I tried the first option but it causes the solver to be very unstable and I cannot get reproducible results even with controlled time step size. Is the second option viable and what is the most robust way of going about this?&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-461409","topic","type-topic","status-publish","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["461409"],"_bbp_subscription":["282802"],"_bbp_author_ip":["194.80.234.171"],"_bbp_last_reply_id":["0"],"_bbp_last_active_id":["461409"],"_bbp_last_active_time":["2026-07-16 10:27:28"],"_bbp_reply_count":["0"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["1"],"_bbp_engagement":["282802"],"_btv_view_count":["38"],"_bbp_topic_status":["unanswered"]},"test":"ll17s5rleeds-ac-uk"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/461409","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\/461409\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=461409"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}