{"id":396850,"date":"2024-12-09T22:23:59","date_gmt":"2024-12-09T22:23:59","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/fsi-coupling\/"},"modified":"2024-12-09T22:26:06","modified_gmt":"2024-12-09T22:26:06","slug":"fsi-coupling","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/fsi-coupling\/","title":{"rendered":"FSI coupling"},"content":{"rendered":"

<p><p>Hi all,<br><br>I am working on this LS-DYNA FSI model with a honeycomb like aluminum structure (red) floating on water (blue) as seen in the attached figure. The structure is made of sixteen chambers – eight on top and eight on bottom, separated by a thin horizontal aluminum layer. The bottom eight chambers are supposed to be filled with air and some water so that the buoyant force keeps the specimen floating on water without the top chambers getting immersed below water level. Both ambient air and trapped air are modeled as an AMMG with a continuous layer right above the water AMMG. I have defined coupling among various parts with Constrained_Lagrange_in_Solid. I am having issues with S-ALE approach so just using traditional ALE approach right now. I cannot use the volume filling keyword for coupling.<br><br>When I gravity initialize the model as shown in the third figure, the code shows error messages saying ‘invalid pointer’. But when I lower the specimen into the water so that the horizontal aluminum partition is below water level then the code progresses without any error message. We have experimental results demonstrating that the specimen should float on water below the partition level so that the bottom eight chambers are partially air filled. The idea is to apply earthquake motions so that those trapped air (between water and the horizontal aluminum layer) provides seismic input attenuation by compressing and expanding during the rocking of the specimen.<br><br>I would like to get your suggestions on how I can -<br>1) gravity initialize this model with the initial specimen position right above the water level? In the attachments, third configuration does not converge but the fourth one does. I wonder if the model is not constrained enough with the third configuration since there is a very small contact between the specimen and the water only by the specimen’s thin edges. But the fourth configuration has more contact with water with the horizontal partition.<br>2) define the coupling between the bottom chambers and air and (b) the bottom chambers and water. In the current model, I have created a LAG seg-set by selecting the interior surfaces of all the bottom eight air chambers and creating two coupling cards – 1. water and seg-set and 2. trapped air and seg-set. Can these coupling cards simulate the compression and expansion of the trapped air?<\/p><p>\"\"\"\"<\/p><p>\"\"\"\"<\/p><\/p><p>Thank you,<\/p><p>Mamun<\/p><\/p>\n","protected":false},"template":"","class_list":["post-396850","topic","type-topic","status-publish","hentry","topic-tag-constraint-issue","topic-tag-contact-and-coupling","topic-tag-fsi-simulation"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27814"],"_bbp_topic_id":["396850"],"_bbp_subscription":["465627","37202"],"_bbp_author_ip":["131.243.224.12"],"_bbp_last_reply_id":["397146"],"_bbp_last_active_id":["397146"],"_bbp_last_active_time":["2024-12-11 17:47:11"],"_bbp_reply_count":["1"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["465627","37202"],"_btv_view_count":["413"],"_bbp_topic_status":["unanswered"],"_bbp_notification_enabled":["465627"],"_edit_last":["465627"],"_bbp_revision_log":["a:1:{i:396851;a:2:{s:6:\"author\";i:465627;s:6:\"reason\";s:0:\"\";}}"]},"test":"mmiahlbl-gov"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/396850","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":1,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/396850\/revisions"}],"predecessor-version":[{"id":396851,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/396850\/revisions\/396851"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=396850"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}