{"id":162054,"date":"2023-01-25T07:34:10","date_gmt":"2023-01-25T07:34:10","guid":{"rendered":"\/knowledge\/forums\/topic\/why-am-i-getting-a-piston-force-with-hsfld242-that-is-1-3rd-what-i-expect\/"},"modified":"2023-07-31T12:36:20","modified_gmt":"2023-07-31T12:36:20","slug":"why-am-i-getting-a-piston-force-with-hsfld242-that-is-1-3rd-what-i-expect","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/why-am-i-getting-a-piston-force-with-hsfld242-that-is-1-3rd-what-i-expect\/","title":{"rendered":"Why am I getting a piston force with hsfld242 that is 1\/3rd what I expect?"},"content":{"rendered":"<p>You need to define the negative fluid volume.  (Structural Analysis Guide Section 18.4: Example model using hydrostatic fluid elements)  Otherwise the fluid volume that is attached to the piston wall doesn&#8217;t change since it is attached to the non-moving mesh of the cylinder.  A good convergence norm for this analysis is HDSP.  Note that the volume of a cone is 1\/3rd the volume of a cylinder of the same height and diameter so the conical fluid volume defined by the piston surface (which is moving) was 1\/3rd the total and produced a force 1\/3rd of the expected value.<\/p>\n","protected":false},"template":"","class_list":["post-162054","topic","type-topic","status-publish","hentry","topic-tag-14-5","topic-tag-fluids","topic-tag-hydrostatic","topic-tag-mechanical-apdl-f-ansys","topic-tag-modeling-and-meshing","topic-tag-structural-mechanics"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_wp_page_template":["default"],"_bbp_forum_id":["27789"],"_bbp_last_active_time":["1-24-2023  20:20:31"],"_bbp_author_ip":["23.56.168.180"],"_btv_view_count":["376"],"siebel_km_number":["2026853"],"product_version":["14.5"],"km_published_date":["2012-12-29T22:16:03.000Z"],"family":["Structural Mechanics"],"application_name":["Mechanical APDL (f. ANSYS)"]},"test":"articlesansys-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/162054","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\/162054\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/media?parent=162054"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}