{"id":164718,"date":"2023-03-17T08:58:30","date_gmt":"2023-03-17T08:58:30","guid":{"rendered":"\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/"},"modified":"2023-07-31T12:26:08","modified_gmt":"2023-07-31T12:26:08","slug":"polyflow-warning-from-frerem-vanishing-norm-for-direction-vector","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/","title":{"rendered":"POLYFLOW &#8211; ***WARNING*** from *frerem*  Vanishing norm for direction vector"},"content":{"rendered":"<p>As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface.  If too much conditions are assigned, it is possible that the calculated direction of motion vanishes.   The trouble typically appears when the direction of motion is zero or is tangential to the free surface. Make sure that the direction of motion do not vanish.  In other words, the selected constraints, if any, should be compatible with the geometry.<\/p>\n","protected":false},"template":"","class_list":["post-164718","topic","type-topic","status-publish","hentry","topic-tag-fluid-dynamics","topic-tag-general","topic-tag-other","topic-tag-polyflow"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<link rel=\"canonical\" href=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/\" \/>\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 Knowledge | Ansys Innovation Space\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"POLYFLOW \u2013 ***WARNING*** from *frerem* Vanishing norm for direction vector | Ansys Knowledge\" \/>\n\t\t<meta property=\"og:description\" content=\"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2023-03-17T08:58:30+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2023-07-31T12:26:08+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"POLYFLOW \u2013 ***WARNING*** from *frerem* Vanishing norm for direction vector | Ansys Knowledge\" \/>\n\t\t<meta name=\"twitter:description\" content=\"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction\" \/>\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\\\/knowledge\\\/forums\\\/topic\\\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\\\/#breadcrumblist\",\"itemListElement\":[{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge#listItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/topics\\\/#listItem\",\"name\":\"Topics\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/topics\\\/#listItem\",\"position\":2,\"name\":\"Topics\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/topics\\\/\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic-tag\\\/fluid-dynamics\\\/#listItem\",\"name\":\"fluid-dynamics\"},\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge#listItem\",\"name\":\"Home\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic-tag\\\/fluid-dynamics\\\/#listItem\",\"position\":3,\"name\":\"fluid-dynamics\",\"item\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic-tag\\\/fluid-dynamics\\\/\",\"nextItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic\\\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\\\/#listItem\",\"name\":\"POLYFLOW &#8211; ***WARNING*** from *frerem*  Vanishing norm for direction vector\"},\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/topics\\\/#listItem\",\"name\":\"Topics\"}},{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic\\\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\\\/#listItem\",\"position\":4,\"name\":\"POLYFLOW &#8211; ***WARNING*** from *frerem*  Vanishing norm for direction vector\",\"previousItem\":{\"@type\":\"ListItem\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic-tag\\\/fluid-dynamics\\\/#listItem\",\"name\":\"fluid-dynamics\"}}]},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/#organization\",\"name\":\"Ansys Knowledge\",\"description\":\"Ansys Innovation Space\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic\\\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\\\/#webpage\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic\\\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\\\/\",\"name\":\"POLYFLOW \\u2013 ***WARNING*** from *frerem* Vanishing norm for direction vector | Ansys Knowledge\",\"description\":\"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction\",\"inLanguage\":\"en-US\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/#website\"},\"breadcrumb\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/forums\\\/topic\\\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\\\/#breadcrumblist\"},\"datePublished\":\"2023-03-17T08:58:30+00:00\",\"dateModified\":\"2023-07-31T12:26:08+00:00\"},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/#website\",\"url\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/\",\"name\":\"Ansys Knowledge\",\"description\":\"Ansys Innovation Space\",\"inLanguage\":\"en-US\",\"publisher\":{\"@id\":\"https:\\\/\\\/innovationspace.ansys.com\\\/knowledge\\\/#organization\"}}]}\n\t\t<\/script>\n\t\t<!-- All in One SEO -->\n\n","aioseo_head_json":{"title":"POLYFLOW \u2013 ***WARNING*** from *frerem* Vanishing norm for direction vector | Ansys Knowledge","description":"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction","canonical_url":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"BreadcrumbList","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/#breadcrumblist","itemListElement":[{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge#listItem","position":1,"name":"Home","item":"https:\/\/innovationspace.ansys.com\/knowledge","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/topics\/#listItem","name":"Topics"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/topics\/#listItem","position":2,"name":"Topics","item":"https:\/\/innovationspace.ansys.com\/knowledge\/topics\/","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluid-dynamics\/#listItem","name":"fluid-dynamics"},"previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge#listItem","name":"Home"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluid-dynamics\/#listItem","position":3,"name":"fluid-dynamics","item":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluid-dynamics\/","nextItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/#listItem","name":"POLYFLOW &#8211; ***WARNING*** from *frerem*  Vanishing norm for direction vector"},"previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/topics\/#listItem","name":"Topics"}},{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/#listItem","position":4,"name":"POLYFLOW &#8211; ***WARNING*** from *frerem*  Vanishing norm for direction vector","previousItem":{"@type":"ListItem","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluid-dynamics\/#listItem","name":"fluid-dynamics"}}]},{"@type":"Organization","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/#organization","name":"Ansys Knowledge","description":"Ansys Innovation Space","url":"https:\/\/innovationspace.ansys.com\/knowledge\/"},{"@type":"WebPage","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/#webpage","url":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/","name":"POLYFLOW \u2013 ***WARNING*** from *frerem* Vanishing norm for direction vector | Ansys Knowledge","description":"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction","inLanguage":"en-US","isPartOf":{"@id":"https:\/\/innovationspace.ansys.com\/knowledge\/#website"},"breadcrumb":{"@id":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/#breadcrumblist"},"datePublished":"2023-03-17T08:58:30+00:00","dateModified":"2023-07-31T12:26:08+00:00"},{"@type":"WebSite","@id":"https:\/\/innovationspace.ansys.com\/knowledge\/#website","url":"https:\/\/innovationspace.ansys.com\/knowledge\/","name":"Ansys Knowledge","description":"Ansys Innovation Space","inLanguage":"en-US","publisher":{"@id":"https:\/\/innovationspace.ansys.com\/knowledge\/#organization"}}]},"og:locale":"en_US","og:site_name":"Ansys Knowledge | Ansys Innovation Space","og:type":"article","og:title":"POLYFLOW \u2013 ***WARNING*** from *frerem* Vanishing norm for direction vector | Ansys Knowledge","og:description":"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction","og:url":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/","article:published_time":"2023-03-17T08:58:30+00:00","article:modified_time":"2023-07-31T12:26:08+00:00","twitter:card":"summary_large_image","twitter:title":"POLYFLOW \u2013 ***WARNING*** from *frerem* Vanishing norm for direction vector | Ansys Knowledge","twitter:description":"As a consequence of this error message, the calculation usually stops. A flow case with free surface may require the calculation of direction of motion for nodal displacements on the free surface. If too much conditions are assigned, it is possible that the calculated direction of motion vanishes. The trouble typically appears when the direction"},"aioseo_meta_data":{"post_id":"164718","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":"2025-10-17 21:34:38","updated":"2026-07-29 14:33:31","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\/knowledge\" 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\/knowledge\/topics\/\" title=\"Topics\">Topics<\/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\/knowledge\/forums\/topic-tag\/fluid-dynamics\/\" title=\"fluid-dynamics\">fluid-dynamics<\/a>\n\t\t<\/span><span class=\"aioseo-breadcrumb-separator\">&raquo;<\/span><span class=\"aioseo-breadcrumb\">\n\t\t\tPOLYFLOW \u2013 ***WARNING*** from *frerem*  Vanishing norm for direction vector\n\t\t<\/span><\/div>","aioseo_breadcrumb_json":[{"label":"Home","link":"https:\/\/innovationspace.ansys.com\/knowledge"},{"label":"Topics","link":"https:\/\/innovationspace.ansys.com\/knowledge\/topics\/"},{"label":"fluid-dynamics","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic-tag\/fluid-dynamics\/"},{"label":"POLYFLOW &#8211; ***WARNING*** from *frerem*  Vanishing norm for direction vector","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/polyflow-warning-from-frerem-vanishing-norm-for-direction-vector\/"}],"acf":[],"custom_fields":[{"0":{"_wp_page_template":["default"],"_bbp_last_active_time":["3-15-2023  20:20:42"],"_bbp_forum_id":["27796"],"_bbp_author_ip":["23.56.168.180"],"_btv_view_count":["376"],"siebel_km_number":["1046"],"product_version":["Other"],"km_published_date":["2004-06-21T00:00:00.000Z"],"family":["Fluid Dynamics"],"application_name":["POLYFLOW"]},"test":"articlesansys-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/164718","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":0,"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/164718\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/media?parent=164718"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}