{"id":158147,"date":"2022-06-06T09:58:49","date_gmt":"2022-06-06T09:58:49","guid":{"rendered":"\/knowledge\/forums\/topic\/in-modal-analysis-the-requested-frequencies-have-been-calculated-which-can-be-seen-in-the-solution-data-but-the-solver-continues-on-to-another-lanczos-cycle-without-converging-further-how-to-stop\/"},"modified":"2022-06-06T09:58:49","modified_gmt":"2022-06-06T09:58:49","slug":"in-modal-analysis-the-requested-frequencies-have-been-calculated-which-can-be-seen-in-the-solution-data-but-the-solver-continues-on-to-another-lanczos-cycle-without-converging-further-how-to-stop","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/in-modal-analysis-the-requested-frequencies-have-been-calculated-which-can-be-seen-in-the-solution-data-but-the-solver-continues-on-to-another-lanczos-cycle-without-converging-further-how-to-stop\/","title":{"rendered":"In modal analysis, the requested frequencies have been calculated which can be seen in the solution data. but the solver continues on to another &#8220;Lanczos cycle&#8221; without converging further. How to stop this?"},"content":{"rendered":"<p>This behavior is most usually due to a very ill-conditioned system. Try changing the solver from Block Lanczos (direct) to subspace.  Subspace better handles indefinite matrices than the Block Lanczos (BL) method.  This can be done in Analysis Settings -> Solver Type -> Subspace. Usually what is happening is that there is a disagreement between the number of modes to be found between what the BL found and what the Sturm sequence check finds.  So a new BL cycle is done with a new shift, but then the same disagreement is found but in the opposite direction.  the subspace does not perform a Sturm check by default, so it can bypass the issue altogether and &#8216;fix&#8217; what is causing the ill conditioned model. But at the expensive of a possible less accurate model.   There is also an option to turn off the Sturm checking for the BL method via the new LANBOPT command.<\/p>\n","protected":false},"template":"","class_list":["post-158147","topic","type-topic","status-publish","hentry","topic-tag-frequency","topic-tag-modal-analysis"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_wp_page_template":["default"],"_bbp_last_active_time":["06-06-2022 20:20"],"_bbp_forum_id":["27792"],"_btv_view_count":["3342"],"_bbp_likes_count":["0"]},"test":"articlesansys-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/topics\/158147","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\/158147\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/knowledge\/wp-json\/wp\/v2\/media?parent=158147"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}