{"id":37111,"date":"2019-08-13T07:58:00","date_gmt":"2019-08-13T07:58:00","guid":{"rendered":"\/forum\/forums\/topic\/ansys-aqwa-modelling-hydrostatic-stiffness\/"},"modified":"2019-08-13T07:58:00","modified_gmt":"2019-08-13T07:58:00","slug":"ansys-aqwa-modelling-hydrostatic-stiffness","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/ansys-aqwa-modelling-hydrostatic-stiffness\/","title":{"rendered":"ANSYS Aqwa &#8211; Modelling Hydrostatic Stiffness"},"content":{"rendered":"<p class=\"MsoNormal\" style=\"line-height: normal; background: white;\"><span style=\"font-size: 10.5pt; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; color: #111111; mso-fareast-language: EN-GB;\">Good afternoon,<\/span><\/p>\n<p><\/p>\n<p class=\"MsoNormal\" style=\"line-height: normal; background: white;\"><span style=\"font-size: 10.5pt; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; color: #111111; mso-fareast-language: EN-GB;\">I am currently modelling a floating structure with ANSYS Aqwa module and I believe there is an incoherence in this when considering the hydrostatic stiffness of the structure. I&#8217;ve run a test in a cylinder where the only restoring surge and sway forces are given by an added stiffness of 10000 and 2500 N\/m, respectively and all other degrees of freedom are blocked. Now, I have inserted an initial displacement in the sway direction of 20 [m] and the forces are correct (20 x 2500 = 50000 [N]). But when I add an initial condition RZ=30&ordm; things don&#8217;t seem to work. As I was trying to understand if the stiffness matrix rotates with the platform I believe two different things can happen:<\/span><\/p>\n<p><\/p>\n<p class=\"MsoNormal\" style=\"line-height: normal; background: white;\"><strong><span style=\"font-size: 10.5pt; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; color: #111111; mso-fareast-language: EN-GB;\">1 &#8211; If the matrix is defined in the global axis<\/span><\/strong><\/p>\n<p><\/p>\n<p class=\"MsoNormal\" style=\"line-height: normal; background: white;\"><span style=\"font-size: 10.5pt; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; color: #111111; mso-fareast-language: EN-GB;\">In this case, the results should be the same as in the situation with RZ=0&ordm;<\/span><\/p>\n<p><\/p>\n<p class=\"MsoNormal\" style=\"line-height: normal; background: white;\"><strong><span style=\"font-size: 10.5pt; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; color: #111111; mso-fareast-language: EN-GB;\">2 &#8211; If the matrix is defined in the local axis<\/span><\/strong><\/p>\n<p><\/p>\n<p class=\"MsoNormal\" style=\"line-height: normal; background: white;\"><span style=\"font-size: 10.5pt; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; color: #111111; mso-fareast-language: EN-GB;\">In this case, the forces should be computed with the respective displacement in the local axis and corresponding stiffness.<\/span><\/p>\n<p><\/p>\n<p class=\"MsoNormal\" style=\"line-height: normal; background: white;\"><span style=\"font-size: 10.5pt; font-family: 'Arial',sans-serif; mso-fareast-font-family: 'Times New Roman'; color: #111111; mso-fareast-language: EN-GB;\">However neither seems to happen. <\/span><\/p>\n","protected":false},"template":"","class_list":["post-37111","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["9286"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["publish"],"_bbp_author_ip":[null],"_bbp_old_sticky_status_id":["normal"],"_bbp_likes_count":["0","0"],"_btv_view_count":["2127"],"_bbp_subscription":["18179"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["37111"],"_bbp_forum_id":["27791"],"_bbp_engagement":["897","18179","158054","167277","169800"],"_bbp_voice_count":["5"],"_bbp_reply_count":["7"],"_bbp_last_reply_id":["304158"],"_bbp_last_active_id":["304158"],"_bbp_last_active_time":["2023-08-30 15:39:39"]},"test":"fcnqp"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/37111","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\/37111\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=37111"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}