{"id":166395,"date":"2022-02-14T22:10:56","date_gmt":"2022-02-14T22:10:56","guid":{"rendered":"\/forum\/forums\/topic\/ansys-insight-slow-convergence-in-fdtd\/"},"modified":"2024-08-26T23:59:14","modified_gmt":"2024-08-26T23:59:14","slug":"ansys-insight-slow-convergence-in-fdtd","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/ansys-insight-slow-convergence-in-fdtd\/","title":{"rendered":"Ansys Insight: Slow convergence in FDTD"},"content":{"rendered":"<div class=\"Item-Body\">\n<div class=\"Message userContent\">\n<p>This post tries to provide some suggestions for the causes and solutions for slow convergence in FDTD. Any other suggestions and experiences are welcome to share here.<\/p>\n<p>In FDTD, it is common that some simulations take long time to converge, or to reach the autoshutoff min. Those are slow convergence cases. Basically, the causes of slow convergence can be classified into three categories: physics, simulation settings, and hardware.<\/p>\n<h2>Physics:<\/h2>\n<p>This type of slow convergence is due to the nature of device-light interaction: the device has strong resonance, and thus it needs long simulation time to converge.<\/p>\n<p>Depending on the final results one desires, such slow convergence may not need to simulate long time:<\/p>\n<ol>\n<li>Q calculation. Time monitors can be used with very short simulation time and the result can be extracted by some post processing. Please refer this article: <a href=\"https:\/\/support.lumerical.com\/hc\/en-us\/articles\/360041611774-Quality-factor-calculations-for-a-resonant-cavity\" rel=\"nofollow\">Quality factor calculations for a resonant cavity<\/a> and Q analysis group.<\/li>\n<li>Field profile for high Q device. Many devices need frequency-domain results, which usually require long simulation time to get <a href=\"\/forum\/index.php?p=\/discussion\/25276\/simulation-time-and-frequency-domain-monitors\" rel=\"nofollow\">accurate Fourier transform<\/a>. If the goal is to get the profile instead of accurate value,&nbsp;the <a href=\"https:\/\/support.lumerical.com\/hc\/en-us\/articles\/360034902473-Understanding-time-apodization-in-frequency-domain-monitors\" rel=\"nofollow\">apodization method<\/a> can be used in the frequency domain monitor. Please refer this example: <a href=\"https:\/\/support.lumerical.com\/hc\/en-us\/articles\/360041611674-Correcting-field-amplitudes-for-high-Q-cavities\" rel=\"nofollow\">Correcting field amplitudes for high-Q cavities<\/a>&nbsp;<\/li>\n<li>Materials with very small real refractive index: very lossy materials require much finer mesh thus very small time step. For example the silver material in visible light. In such cases, long simulation with slow convergence is normal.<\/li>\n<\/ol>\n<h2><\/h2>\n","protected":false},"template":"","class_list":["post-166395","topic","type-topic","status-publish","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_btv_view_count":["2228"],"_bbp_likes_count":["1"],"_bbp_subscription":["2592"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["166395"],"_bbp_forum_id":["27833"],"_bbp_engagement":["2592"],"_bbp_voice_count":["1"],"_bbp_reply_count":["1"],"_bbp_last_reply_id":["205484"],"_bbp_last_active_id":["205484"],"_bbp_last_active_time":["2022-02-14 22:38:38"],"_bbp_notification_enabled":["498852"]},"test":"gsun"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/166395","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\/166395\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=166395"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}