{"id":199057,"date":"2026-06-26T19:46:41","date_gmt":"2026-06-26T19:46:41","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/knowledge\/?post_type=topic&#038;p=199057"},"modified":"2026-06-26T19:47:09","modified_gmt":"2026-06-26T19:47:09","slug":"how-do-i-define-where-refinement-should-occur-with-sph-adaptive-size-in-ansys-freeflow","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/how-do-i-define-where-refinement-should-occur-with-sph-adaptive-size-in-ansys-freeflow\/","title":{"rendered":"How do I define where refinement should occur with SPH Adaptive size in Ansys FreeFlow?"},"content":{"rendered":"<h1  id=\"\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-198650 size-full\" src=\"https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2.png\" alt=\"\" width=\"1600\" height=\"200\" srcset=\"https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2.png 1600w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2-300x38.png 300w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2-1024x128.png 1024w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2-768x96.png 768w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2-1536x192.png 1536w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2-24x3.png 24w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2-36x5.png 36w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/05\/Freeflow-FAQ-banner-v2-48x6.png 48w\" sizes=\"auto, (max-width: 1600px) 100vw, 1600px\" \/><\/h1>\n<h1  id=\"HOW-DO-I-DEFINE-WHERE-REFINEMENT-SHOULD-OCCUR-WITH-SPH-ADAPTIVE-SIZE-IN-ANSYS-FREEFLOW\"><strong>How do I define where refinement should occur with SPH Adaptive size in Ansys FreeFlow?<\/strong><\/h1>\n<div>\n<div class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">Ansys FreeFlow provides three approaches for defining refinement regions:<\/div>\n<h3  id=\"1-GEOMETRY-BOUNDARY-REFINEMENT\">1. Geometry Boundary Refinement<\/h3>\n<div class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">Refinement is applied based on proximity to selected geometry boundaries (walls).<br \/>\nYou specify:<\/div>\n<ul>\n<li class=\"___ccc16d0 fje8fi8 f1ng9h0j f1bwykku f18jd3zf\">A Refinement Distance Factor<\/li>\n<li class=\"___ccc16d0 fje8fi8 f1ng9h0j f1bwykku f18jd3zf\">A Refinement Level<\/li>\n<\/ul>\n<div class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">A refinement zone is computed as:<\/div>\n<div><\/div>\n<pre class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">Refinement Distance = Refinement Distance Factor \u00d7 Initial SPH Size<\/pre>\n<div><\/div>\n<div class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">All SPH elements within this distance from the selected geometry are refined. The refinement region is subdivided into volumes proportional to its size, with refinement levels that increase gradually across these partitions. The figure below provides a schematic representation of this process.<\/div>\n<\/div>\n<div><\/div>\n<div><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-199058 aligncenter\" src=\"https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/06\/Picture1.png\" alt=\"\" width=\"220\" height=\"304\" srcset=\"https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/06\/Picture1.png 451w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/06\/Picture1-217x300.png 217w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/06\/Picture1-17x24.png 17w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/06\/Picture1-26x36.png 26w, https:\/\/innovationspace.ansys.com\/knowledge\/wp-content\/uploads\/sites\/4\/2026\/06\/Picture1-35x48.png 35w\" sizes=\"auto, (max-width: 220px) 100vw, 220px\" \/><\/div>\n<div>\n<h3  id=\"2-CUBIC-REGION-OF-INTEREST-ROI\">2. Cubic Region of Interest (ROI)<\/h3>\n<div class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">You define a cube-shaped region in space. All SPH elements inside the cube are refined according to the selected refinement level.<br \/>\nThis approach is useful for localized flow features such as impacts, mixing zones, or free surface interactions.<\/div>\n<h3  id=\"3-CYLINDRICAL-REGION-OF-INTEREST-ROI\">3. Cylindrical Region of Interest (ROI)<\/h3>\n<div class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">You define a cylindrical region in which SPH elements are refined.<\/div>\n<ul>\n<li class=\"___ccc16d0 fje8fi8 f1ng9h0j f1bwykku f18jd3zf\"><strong>If no hole ratio is specified:<\/strong>\n<ul>\n<li class=\"___ccc16d0 fje8fi8 f1ng9h0j f1bwykku f18jd3zf\">All elements inside the cylinder are refined<\/li>\n<\/ul>\n<\/li>\n<li class=\"___ccc16d0 fje8fi8 f1ng9h0j f1bwykku f18jd3zf\"><strong>If a hole ratio is specified:<\/strong>\n<ul>\n<li class=\"___ccc16d0 fje8fi8 f1ng9h0j f1bwykku f18jd3zf\">Only elements outside the hole region are refined<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<div class=\"paragraph-in-scc-markdown-text ___1ngh792 ftgm304 f1iaxwol\">This is particularly useful for pipes, jets, nozzles, and axis-aligned flow features. The user can combine different ROI geometries and set one refinement level for each ROI.<\/div>\n<\/div>\n<div><\/div>\n<div>\n<div class=\"packages-rocky\">\n<div class=\"additional-package-rocky col-md-5\">\n<p>Access more FAQs and Tips in the page:<\/p>\n<div><a class=\"download\" href=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/ansys-freeflow-faqs-and-tips\/\" target=\"_blank\" rel=\"noopener\">FreeFlow FAQs and Tips<\/a><\/div>\n<\/div>\n<\/div>\n<div>\n<h6 class=\"paragraph\" style=\"text-align: center\" align=\"right\" class=\"paragraph\" style=\"text-align: center\" align=\"right\"  id=\"ANSYS-FREEFLOW-SMOOTHED-PARTICLE-HYDRODYNAMICS-SPH-SIMULATION-SOFTWARE\"><span class=\"eop\"><span style=\"font-size: 16.0pt\"><em>Ansys FreeFlow\u2122 smoothed-particle hydrodynamics (SPH) simulation software<\/em><\/span><\/span><\/h6>\n<\/div>\n<\/div>\n","protected":false},"template":"","class_list":["post-199057","topic","type-topic","status-publish","hentry","topic-tag-ansys-freeflow","topic-tag-ansys-freeflow-content","topic-tag-ansys-freeflow-faqs","topic-tag-ansys-freeflow-sph","topic-tag-freeflow-refinement","topic-tag-sph-adaptive-size","topic-tag-sph-faqs","filter-by-application-ansys-freeflow","application-products-ansys-freeflow"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_edit_lock":["1782505033:17114"],"_edit_last":["17114"],"_aioseo_title":[null],"_aioseo_description":[null],"_aioseo_keywords":["a:0:{}"],"_aioseo_og_title":[null],"_aioseo_og_description":[null],"_aioseo_og_article_section":[""],"_aioseo_og_article_tags":["a:0:{}"],"_aioseo_twitter_title":[null],"_aioseo_twitter_description":[null],"application_name":[""],"_application_name":["field_64a80903c8e15"],"filter_by_optics_product":["Lumerical"],"_filter_by_optics_product":["field_64fb192ba3121"],"family":[""],"_family":["field_64a809229a857"],"siebel_km_number":[""],"_siebel_km_number":["field_63ecbffce60db"],"salesforce_km_number":[""],"_salesforce_km_number":["field_63ecc018e60dc"],"km_published_date":[""],"_km_published_date":["field_64c77704499dd"],"product_version":[""],"_product_version":["field_64c776cb4fd2e"],"_bbp_forum_id":["27796"],"_bbp_topic_id":["199057"],"_bbp_author_ip":["192.104.24.234"],"_bbp_last_reply_id":["0"],"_bbp_last_active_id":["199059"],"_bbp_last_active_time":["2026-06-26 19:46:41"],"_bbp_reply_count":["0"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["0"],"_btv_view_count":["108"],"_bbp_likes_count":["1"]},"test":"articlesansys-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/199057","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":1,"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/199057\/revisions"}],"predecessor-version":[{"id":199059,"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/199057\/revisions\/199059"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/media?parent=199057"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}