{"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":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Hello,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\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/\" \/>\n\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 4.9.10\" \/>\n\t\t<meta property=\"og:locale\" content=\"en_US\" \/>\n\t\t<meta property=\"og:site_name\" content=\"Ansys Learning Forum | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"Simulating Semi-Batch Process (Change Velocity) | Ansys Learning Forum\" \/>\n\t\t<meta property=\"og:description\" content=\"Hello,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\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2026-07-16T10:27:28+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2026-07-16T10:27:28+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"Simulating Semi-Batch Process (Change Velocity) | Ansys Learning Forum\" \/>\n\t\t<meta name=\"twitter:description\" content=\"Hello,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\" \/>\n\t\t<script type=\"application\/ld+json\" class=\"aioseo-schema\">\n\t\t\t{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/simulating-semi-batch-process-change-velocity\\\/#breadcrumblist\",\"itemListElement\":[{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/#listItem\",\"name\":\"Topics\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/#listItem\",\"position\":2,\"name\":\"Topics\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/simulating-semi-batch-process-change-velocity\\\/#listItem\",\"name\":\"Simulating Semi-Batch Process (Change Velocity)\"},\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum#listItem\",\"name\":\"Home\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/simulating-semi-batch-process-change-velocity\\\/#listItem\",\"position\":3,\"name\":\"Simulating Semi-Batch Process (Change Velocity)\",\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/topics\\\/#listItem\",\"name\":\"Topics\"}}]},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#organization\",\"name\":\"Ansys Learning Forum\",\"description\":\"Ansys Innovation Space\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/simulating-semi-batch-process-change-velocity\\\/#webpage\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/simulating-semi-batch-process-change-velocity\\\/\",\"name\":\"Simulating Semi-Batch Process (Change Velocity) | Ansys Learning Forum\",\"description\":\"Hello,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\",\"inLanguage\":\"en-US\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#website\"},\"breadcrumb\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/forums\\\/topic\\\/simulating-semi-batch-process-change-velocity\\\/#breadcrumblist\"},\"datePublished\":\"2026-07-16T10:27:28+00:00\",\"dateModified\":\"2026-07-16T10:27:28+00:00\"},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#website\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/\",\"name\":\"Ansys Learning Forum\",\"description\":\"Ansys Innovation Space\",\"inLanguage\":\"en-US\",\"publisher\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/forum\\\/#organization\"}}]}\n\t\t<\/script>\n\t\t<!-- All in One SEO -->\n\n","aioseo_head_json":{"title":"Simulating Semi-Batch Process (Change Velocity) | Ansys Learning Forum","description":"Hello,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","canonical_url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"BreadcrumbList","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/#breadcrumblist","itemListElement":[{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum#listItem","position":1,"name":"Home","item":"https:\/\/innovationspace.ansys.com\/forum","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/topics\/#listItem","name":"Topics"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/topics\/#listItem","position":2,"name":"Topics","item":"https:\/\/innovationspace.ansys.com\/forum\/topics\/","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/#listItem","name":"Simulating Semi-Batch Process (Change Velocity)"},"previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum#listItem","name":"Home"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/#listItem","position":3,"name":"Simulating Semi-Batch Process (Change Velocity)","previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/forum\/topics\/#listItem","name":"Topics"}}]},{"@type":"Organization","@id":"https:\/\/innovationspace.ansys.com\/forum\/#organization","name":"Ansys Learning Forum","description":"Ansys Innovation Space","url":"https:\/\/innovationspace.ansys.com\/forum\/"},{"@type":"WebPage","@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/#webpage","url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/","name":"Simulating Semi-Batch Process (Change Velocity) | Ansys Learning Forum","description":"Hello,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","inLanguage":"en-US","isPartOf":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/#website"},"breadcrumb":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/#breadcrumblist"},"datePublished":"2026-07-16T10:27:28+00:00","dateModified":"2026-07-16T10:27:28+00:00"},{"@type":"WebSite","@id":"https:\/\/innovationspace.ansys.com\/forum\/#website","url":"https:\/\/innovationspace.ansys.com\/forum\/","name":"Ansys Learning Forum","description":"Ansys Innovation Space","inLanguage":"en-US","publisher":{"@id":"https:\/\/innovationspace.ansys.com\/forum\/#organization"}}]},"og:locale":"en_US","og:site_name":"Ansys Learning Forum | Ansys Innovation Space","og:type":"article","og:title":"Simulating Semi-Batch Process (Change Velocity) | Ansys Learning Forum","og:description":"Hello,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","og:url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/","article:published_time":"2026-07-16T10:27:28+00:00","article:modified_time":"2026-07-16T10:27:28+00:00","twitter:card":"summary_large_image","twitter:title":"Simulating Semi-Batch Process (Change Velocity) | Ansys Learning Forum","twitter:description":"Hello,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"},"aioseo_meta_data":{"post_id":"461409","title":null,"description":null,"keywords":null,"keyphrases":null,"primary_term":null,"canonical_url":null,"og_title":null,"og_description":null,"og_object_type":"default","og_image_type":"default","og_image_url":null,"og_image_width":null,"og_image_height":null,"og_image_custom_url":null,"og_image_custom_fields":null,"og_video":null,"og_custom_url":null,"og_article_section":null,"og_article_tags":null,"twitter_use_og":false,"twitter_card":"default","twitter_image_type":"default","twitter_image_url":null,"twitter_image_custom_url":null,"twitter_image_custom_fields":null,"twitter_title":null,"twitter_description":null,"schema":{"blockGraphs":[],"customGraphs":[],"default":{"data":{"Article":[],"Course":[],"Dataset":[],"FAQPage":[],"Movie":[],"Person":[],"Product":[],"ProductReview":[],"Car":[],"Recipe":[],"Service":[],"SoftwareApplication":[],"WebPage":[]},"graphName":"","isEnabled":true},"graphs":[]},"schema_type":"default","schema_type_options":null,"pillar_content":false,"robots_default":true,"robots_noindex":false,"robots_noarchive":false,"robots_nosnippet":false,"robots_nofollow":false,"robots_noimageindex":false,"robots_noodp":false,"robots_notranslate":false,"robots_max_snippet":null,"robots_max_videopreview":null,"robots_max_imagepreview":"large","priority":null,"frequency":null,"local_seo":null,"limit_modified_date":false,"created":"2026-07-16 10:42:03","updated":"2026-07-16 10:42:03","ai":null,"breadcrumb_settings":null,"seo_analyzer_scan_date":null},"aioseo_breadcrumb":"<div class=\"aioseo-breadcrumbs\"><span class=\"aioseo-breadcrumb\">\n\t\t\t<a href=\"https:\/\/innovationspace.ansys.com\/forum\" title=\"Home\">Home<\/a>\n\t\t<\/span><span class=\"aioseo-breadcrumb-separator\">&raquo;<\/span><span class=\"aioseo-breadcrumb\">\n\t\t\t<a href=\"https:\/\/innovationspace.ansys.com\/forum\/topics\/\" title=\"Topics\">Topics<\/a>\n\t\t<\/span><span class=\"aioseo-breadcrumb-separator\">&raquo;<\/span><span class=\"aioseo-breadcrumb\">\n\t\t\tSimulating Semi-Batch Process (Change Velocity)\n\t\t<\/span><\/div>","aioseo_breadcrumb_json":[{"label":"Home","link":"https:\/\/innovationspace.ansys.com\/forum"},{"label":"Topics","link":"https:\/\/innovationspace.ansys.com\/forum\/topics\/"},{"label":"Simulating Semi-Batch Process (Change Velocity)","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/simulating-semi-batch-process-change-velocity\/"}],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["461409"],"_bbp_subscription":["282802","711628"],"_bbp_author_ip":["194.80.234.171"],"_bbp_last_reply_id":["461729"],"_bbp_last_active_id":["461729"],"_bbp_last_active_time":["2026-07-23 10:23:42"],"_bbp_reply_count":["2"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["282802","711628"],"_btv_view_count":["111"],"_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}]}}