{"id":383069,"date":"2024-09-19T04:28:47","date_gmt":"2024-09-19T04:28:47","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/changing-the-boundary-condition-after-flow-time-gt-1s\/"},"modified":"2024-09-19T04:28:47","modified_gmt":"2024-09-19T04:28:47","slug":"changing-the-boundary-condition-after-flow-time-gt-1s","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/changing-the-boundary-condition-after-flow-time-gt-1s\/","title":{"rendered":"Changing the boundary condition after flow time &gt; 1s"},"content":{"rendered":"<p>&lt;p&gt;Hi,&lt;\/p&gt;&lt;p&gt;I&#8217;m running a transient simulation with some user defined scalars. One of the uds is space charge and have the unit Coulombs\/kg (C\/kg). The UDS is implemented using the default unsteady function and mass flux as the flux function.&nbsp;&lt;\/p&gt;&lt;p&gt;On a wall, I want to set zero flux boundary condition on the space charge uds initially. However, after a flowtime of more than 1 second. I want the wall to act as a sink that depletes that uds at a rate of 0.1 C\/(m^2.s).&lt;\/p&gt;&lt;p&gt;I would like to know if the following method correct:&nbsp;&lt;\/p&gt;&lt;p&gt;1. Set the bc of the wall as &#8220;specified flux&#8221; and set the value as an expression. The expression is &#8220;if(t&gt;1[s], 0.1, 0)&#8221;&lt;\/p&gt;&lt;p&gt;I don&#8217;t think it is right, cause the expression always yield to 0, how do I implement this?&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&nbsp;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-383069","topic","type-topic","status-publish","hentry","topic-tag-boundary-conditions","topic-tag-transient"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["451626","199842","13659"],"_bbp_author_ip":["193.114.139.226"],"_btv_view_count":["309"],"_bbp_topic_status":["unanswered"],"_bbp_likes_count":["1"],"_bbp_topic_id":["383069"],"_bbp_forum_id":["27792"],"_bbp_engagement":["13659","199842","451626"],"_bbp_voice_count":["3"],"_bbp_reply_count":["3"],"_bbp_last_reply_id":["388054"],"_bbp_last_active_id":["388054"],"_bbp_last_active_time":["2024-10-03 19:50:46"]},"test":"adi959719gmail-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/383069","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\/383069\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=383069"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}