{"id":349759,"date":"2024-02-07T21:21:21","date_gmt":"2024-02-07T21:21:21","guid":{"rendered":"\/forum\/forums\/topic\/negative-internal-energy-in-sph-simulation\/"},"modified":"2024-02-07T21:21:21","modified_gmt":"2024-02-07T21:21:21","slug":"negative-internal-energy-in-sph-simulation","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/negative-internal-energy-in-sph-simulation\/","title":{"rendered":"Negative internal energy in SPH simulation"},"content":{"rendered":"<p>Hello,<\/p>\n<p>&nbsp;<\/p>\n<p>When I use LS-Prepost to read the result files, I find that for some cases, the total internal energy will appear an extremely negative value:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/02\/07-02-2024-1707339972-mceclip0.png\"><\/p>\n<p>Also, the total kinetic energy cannot be fully displayed (as you can see, the same part but with different time frames, it should end at 10^-6s but there is no output after 8^-6s):<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/02\/07-02-2024-1707340048-mceclip1.png\"><\/p>\n<p>However, the results are convergent for other cases (same model but with different material properties). Also, for different meshes, the results will be different as well.<\/p>\n<p>&nbsp;<\/p>\n<p>What I want to ask is:<\/p>\n<ol>\n<li>I suppose that it will be a numerical error in LS-DYNA. Are there any methods to solve it? For example, to set a smaller time step size or change some other settings in LS-Run?<\/li>\n<li>Are there any methods in LS-Prepost to directly output the particle (nodal) internal energy? I can find the icon (internal energy in SPH Fringe Comp) but I cannot find internal energy in the history output icon, only part energy, which shows the same results as matsum. If I can get the individual results, I can manually delete the extreme particles and see the results.<\/li>\n<li>&nbsp;<\/li>\n<li><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/02\/07-02-2024-1707340581-mceclip2.png\"><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/02\/07-02-2024-1707340725-mceclip3.png\"><\/li>\n<\/ol>\n<p>Best,<\/p>\n<p>Rong<\/p>\n","protected":false},"template":"","class_list":["post-349759","topic","type-topic","status-closed","hentry","topic-tag-energy-error","topic-tag-ls-dyna","topic-tag-sph"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["22672","13468"],"_bbp_author_ip":["23.218.248.135"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["812"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["349759"],"_bbp_forum_id":["27814"],"_bbp_engagement":["13468","22672"],"_bbp_voice_count":["2"],"_bbp_reply_count":["2"],"_bbp_last_reply_id":["357665"],"_bbp_last_active_id":["357665"],"_bbp_last_active_time":["2024-03-18 15:03:24"]},"test":"rji229uky-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/349759","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\/349759\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=349759"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}