{"id":393679,"date":"2024-11-12T01:56:55","date_gmt":"2024-11-12T01:56:55","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/general-inquiries-about-how-to-use-pseudo-transient-under-relaxation\/"},"modified":"2024-11-12T01:56:55","modified_gmt":"2024-11-12T01:56:55","slug":"general-inquiries-about-how-to-use-pseudo-transient-under-relaxation","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/general-inquiries-about-how-to-use-pseudo-transient-under-relaxation\/","title":{"rendered":"General Inquiries about how to use Pseudo transient Under-relaxation"},"content":{"rendered":"<p>&lt;p&gt;Hello! I&#8217;m using pseudo-transient to help dampen the solution&#8217;s oscillations for my steady-state simulation, but I&#8217;m not sure if my approach is correct, mainly with how to calculate the pseudo time step.&lt;\/p&gt;&lt;p&gt;I know Fluent&#8217;s defaults seem to do something like one-third of the flow-through time (length of domain divided by representative velocity), but is there a benefit to reducing the time-step further? The flow-through time for my model is about 1 second, so I tried 0.1 to start but didn&#8217;t see much reduction in the solution&#8217;s oscillations.&lt;\/p&gt;&lt;p&gt;When I went as far down as 1e-5 seconds, I satrted to see the residuals go down to a much lower value and the oscillations seem to die out, but this seems to be extreme compared to what I&#8217;ve read in the fluent user guide. They suggest values within an order of magnitude of the flow-through time, but the pseudo-time-step I applied is much much smaller.&nbsp;&lt;\/p&gt;&lt;p&gt;For reference, I&#8217;m performing about 13,000 iterations, which also seems pretty extreme from what I would expect. The flow is an internal, incompressible flow and is using the k-omega sst turbulence model.&nbsp;&lt;\/p&gt;&lt;p&gt;Any guidance?&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-393679","topic","type-topic","status-publish","hentry","topic-tag-fluent","topic-tag-pseudo-transient","topic-tag-steady-state"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":["98.239.138.115"],"_btv_view_count":["1646"],"_bbp_topic_status":["unanswered"],"_bbp_subscription":["199"],"_bbp_topic_id":["393679"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","240657"],"_bbp_voice_count":["2"],"_bbp_reply_count":["1"],"_bbp_last_reply_id":["393762"],"_bbp_last_active_id":["393762"],"_bbp_last_active_time":["2024-11-12 11:18:16"]},"test":"nobrienandrew-cmu-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/393679","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\/393679\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=393679"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}