{"id":165423,"date":"2022-01-10T20:16:46","date_gmt":"2022-01-10T20:16:46","guid":{"rendered":"\/forum\/forums\/topic\/ansys-workbench-harmonic-response-expansion-pass\/"},"modified":"2022-01-13T09:56:52","modified_gmt":"2022-01-13T09:56:52","slug":"ansys-workbench-harmonic-response-expansion-pass","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/ansys-workbench-harmonic-response-expansion-pass\/","title":{"rendered":"ANSYS Workbench Harmonic Response Expansion Pass"},"content":{"rendered":"
\n
\n

I am a relatively new ANSYS user trying to find my way after years of using NASTRAN with PATRAN & FEMAP. I have found that some problems I want to solve are far more intuitive and powerful in ANSYS but some things remain very frustrating. I am hoping someone can help me to understand this one!<\/p>\n

I am using ANSYS 2021R1. In Workbench I have a modestly sized shell element model (~65K nodes and elements) that I am running a base acceleration analysis on with the intent of developing base drive transfer functions to a small number of nodes. To do this I have a Modal system feeding three Harmonic Response systems. The Modal system has the structure in question grounded at its base. Each of the Harmonic Response systems has a 0-300Hz 1g acceleration load applied as a base excitation applied in either the X, Y, or Z axes. I am using the modal superposition technique. The structure in question has about 50 modes in the analysis frequency range.<\/p>\n

Everything works just fine and I can get the answers that I want. The issue that I have is that the MSUP expansion pass ("Expanding Harmonic Solution") step takes A LONG TIME. The modal solution and harmonic solution take maybe 10 minutes; the harmonic expansion pass takes ~3 hours (depending on the # of frequency points etc.) This really surprises me because I am only recovering displacement results – so what is ANSYS doing for all that time? My NASTRAN experience tells me that somehow I should be able to get the solver to spit out what I want in far less time.<\/p>\n

I have tried a few things to speed things up with no significant change in compute time: <\/p>\n

1.) I have turned off all of the un-needed output requests (all of them, in fact…) in the harmonic solution.<\/p>\n

2.) I have tried reducing the number of results stored in the .rst file using OUTRES commands in a APDL command snippet. <\/p>\n

3.) Just to mention it, "Skip Expansion" does not work because of the base excitation input.<\/p>\n

I'm wondering if the last point is really the issue – does ANSYS need to do a larger expansion to apply the base excitation? Can I get around this by applying the base excitation another way; i.e. large mass method?<\/p>\n

I'm sure my not understanding this problem has to do with the script-like execution of ANSYS vs. the deck\/batch-like execution of NASTRAN. Can anyone offer any insight \/ tips to speed up my solve? I can of course provide more details if necessary.<\/p>\n","protected":false},"template":"","class_list":["post-165423","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":[""],"_bbp_old_reply_author_name_id":["Anonymous"],"_bbp_old_is_reply_anonymous_id":["false"],"_btv_view_count":["5770"],"_bbp_likes_count":["0"],"_bbp_subscription":["237369"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["165423"],"_bbp_forum_id":["27791"],"_bbp_engagement":["58821","166004","219634","235392"],"_bbp_voice_count":["4"],"_bbp_reply_count":["16"],"_bbp_last_reply_id":["202416"],"_bbp_last_active_id":["202416"],"_bbp_last_active_time":["2022-01-13 09:56:52"]},"test":"msoflle-rochester-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/165423","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\/165423\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=165423"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}